Simplified approach to computer science Sir Wagner ™ ii TABLE OF CONTENTS Contents TABLE OF CONTENTS ........................................................................................................................... II INTRODUCTION TO COMPUTER SCIENCE ........................................................................................... 1 DEFINITION OF A COMPUTER .............................................................................................................. 1 Components of a computer ....................................................................................................................... 1 CLASSIFICATION OF COMPUTERS ....................................................................................................... 1 Super computer ......................................................................................................................................... 1 Characteristics ........................................................................................................................................... 1 Mainframe computers ............................................................................................................................... 1 Characteristics ........................................................................................................................................... 2 Mini computers ......................................................................................................................................... 2 Characteristics ........................................................................................................................................... 2 Desktop computers.................................................................................................................................... 2 Characteristics ........................................................................................................................................... 2 HARD WARE AND SOFTWARE ............................................................................................................. 3 HARDWARE ........................................................................................................................................... 3 Categories of hardware ............................................................................................................................. 3 INPUT DEVICES ..................................................................................................................................... 3 OUTPUT DEVICES ................................................................................................................................. 3 STORAGE DEVICES .............................................................................................................................. 6 APPLICATION OF HARDWARE DEVICES ............................................................................................ 8 Point of sale (POS) terminal ..................................................................................................................... 8 Automated Teller Machine (ATM) ........................................................................................................... 8 Components of an ATM ........................................................................................................................... 9 Data capturing systems ............................................................................................................................. 9 shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ iii SOFTWARE ........................................................................................................................................... 10 Classes of software ................................................................................................................................. 10 APPLICATION SOFTWARE ................................................................................................................ 10 General purpose software ....................................................................................................................... 10 Special purpose software ........................................................................................................................ 10 Off the shelf software.............................................................................................................................. 10 Customised software ............................................................................................................................... 11 SYSTEMS SOFTWARE ........................................................................................................................ 11 Operating System .................................................................................................................................... 12 Functions of operating system ................................................................................................................ 12 Types of operating systems ..................................................................................................................... 13 Personal computer operating system....................................................................................................... 13 Utilities.................................................................................................................................................... 14 Language translators ............................................................................................................................... 14 HARDWARE AND SOFTWARE MAINTENANCE ................................................................................. 14 Relationship between hardware and software ......................................................................................... 14 Troubleshooting ...................................................................................................................................... 14 COMPUTER NETWORKS AND INTERNET TECHNOLOGIES .............................................................. 15 COMPUTER NETWORKS ...................................................................................................................... 15 Reasons for networking .......................................................................................................................... 15 Advantages of Networking ..................................................................................................................... 15 Disadvantages of Networking ................................................................................................................. 15 Network architectures ............................................................................................................................. 15 Peer to peer network ............................................................................................................................... 15 Classification of networks....................................................................................................................... 16 Classes of Networks ................................................................................................................................ 16 LANS and WANS................................................................................................................................... 16 Local area network.................................................................................................................................. 16 Pan and can ............................................................................................................................................. 16 Wide area network .................................................................................................................................. 16 Network topologies ................................................................................................................................. 16 Topologies include .................................................................................................................................. 16 Bus topology: .......................................................................................................................................... 16 shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ iv Star topology: .......................................................................................................................................... 16 Ring network topology ........................................................................................................................... 16 Advantages of Ring Network.................................................................................................................. 17 Disadvantages of Ring Network ............................................................................................................. 17 Mesh Network......................................................................................................................................... 17 Advantages of Mesh Network................................................................................................................. 17 Disadvantages of Mesh Network ............................................................................................................ 17 INTERNET SERVICES ........................................................................................................................... 17 Email ....................................................................................................................................................... 17 E-commerce ............................................................................................................................................ 17 E-learning................................................................................................................................................ 18 Social media ............................................................................................................................................ 18 DATA TRANSMISSION ......................................................................................................................... 18 Data transmission modes ........................................................................................................................ 18 Full duplex/Duplex ................................................................................................................................. 18 Advantages of Duplex............................................................................................................................. 18 Half Duplex transmission modes ............................................................................................................ 19 Advantages of Half Duplex Transmission .............................................................................................. 19 Simplex transmission .............................................................................................................................. 19 Advantages.............................................................................................................................................. 19 DATA TRANSMISSION MEDIA ............................................................................................................ 19 Bounded media ....................................................................................................................................... 19 Twisted pair cable ................................................................................................................................... 19 Characteristics of twisted pair cables ...................................................................................................... 20 Coaxial cable........................................................................................................................................... 20 Characteristics ......................................................................................................................................... 20 Fibre optic cable...................................................................................................................................... 20 Fibre optic cable characteristics .............................................................................................................. 20 Unbounded transmission media .............................................................................................................. 20 Radio transmission .................................................................................................................................. 20 Characteristics of radio frequency transmission ..................................................................................... 20 Microwave transmission ......................................................................................................................... 21 shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ v Satellite transmission .............................................................................................................................. 21 Internet service providers ........................................................................................................................ 21 Services offered by ISPs ......................................................................................................................... 21 MOBILE TECHNOLOGIES .................................................................................................................... 21 Mobile phone .......................................................................................................................................... 21 Feature phone .......................................................................................................................................... 21 Smartphones............................................................................................................................................ 21 Satellite communication.......................................................................................................................... 21 PDA Personal digital assistant ................................................................................................................ 22 Tablet ...................................................................................................................................................... 22 Application of mobile technologies ........................................................................................................ 22 Agriculture .............................................................................................................................................. 22 Communication ....................................................................................................................................... 22 Entertainment .......................................................................................................................................... 22 Education ................................................................................................................................................ 22 Mobile shopping ..................................................................................................................................... 23 Mobile banking ....................................................................................................................................... 23 Mobile marketing .................................................................................................................................... 23 WIRELESS TECHNOLOGIES ............................................................................................................... 23 WiFi ........................................................................................................................................................ 23 WiMax .................................................................................................................................................... 23 Bluetooth ................................................................................................................................................. 24 Infrared.................................................................................................................................................... 24 Microwave .............................................................................................................................................. 24 COMMUNICATION PROTOCOLS ........................................................................................................ 24 Networking hardware.............................................................................................................................. 24 Network interface card ............................................................................................................................ 24 Modem .................................................................................................................................................... 25 Switch ..................................................................................................................................................... 25 shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ vi SECURITY AND ETHICS ..................................................................................................................... 26 COMPUTER VIRUS .............................................................................................................................. 26 How does it affect a computer?............................................................................................................... 26 How do viruses spread? .......................................................................................................................... 26 Methods of preventing viruses ................................................................................................................ 26 Ethics ...................................................................................................................................................... 26 Cyber security ......................................................................................................................................... 26 CYBER WELLNESS .............................................................................................................................. 27 Importance of cyber wellness ................................................................................................................. 27 Cyber use ................................................................................................................................................ 27 Characteristics of safe and unsafe sites ................................................................................................... 27 Signs of a safe website ............................................................................................................................ 27 Signs of an unsafe website ...................................................................................................................... 27 Handling online content and behavior .................................................................................................... 27 Online Relationships ............................................................................................................................... 28 COPYRIGHT ISSUES ............................................................................................................................ 28 Copyright ................................................................................................................................................ 28 Copyright infringement ........................................................................................................................... 28 Importance of copyrights ........................................................................................................................ 28 PLAGIARISM AND PIRACY ................................................................................................................ 28 Plagiarism ............................................................................................................................................... 28 Consequences of plagiarism.................................................................................................................... 28 Piracy ...................................................................................................................................................... 28 Consequences of piracy .......................................................................................................................... 28 COMPUTER CRIME.............................................................................................................................. 29 Data protection measures ........................................................................................................................ 29 COMPUTER ETHICS ............................................................................................................................ 29 The ten commandments of computer ethics ........................................................................................... 29 shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ vii PRIVACY .............................................................................................................................................. 29 DATA INTEGRITY ............................................................................................................................... 30 It may be compromised by ...................................................................................................................... 30 Data integrity best practices include: ...................................................................................................... 30 DATA VERIFICATION ......................................................................................................................... 30 Data validation methods ......................................................................................................................... 30 DATA VALIDATION ............................................................................................................................ 30 Data validation methods ......................................................................................................................... 30 SYSTEM SECURITY .............................................................................................................................. 31 Network security measures ..................................................................................................................... 31 Fire wall .................................................................................................................................................. 31 Intrusion detection system IDS ............................................................................................................... 31 Types ....................................................................................................................................................... 31 Proxy server ............................................................................................................................................ 31 Encryption ............................................................................................................................................... 31 Additional safeguards to computer network and data ............................................................................. 32 CYBER CRIME ..................................................................................................................................... 32 Common types of cybercrime ................................................................................................................. 32 Effects of cybercrime .............................................................................................................................. 32 Examples of cyber crime ........................................................................................................................ 32 Spoofing .................................................................................................................................................. 32 Sniffing ................................................................................................................................................... 32 Fraud ....................................................................................................................................................... 32 Hacking ................................................................................................................................................... 32 DATA BACKUP .................................................................................................................................... 33 Reasons for backup ................................................................................................................................. 33 Backup hardware .................................................................................................................................... 33 Magnetic tape .......................................................................................................................................... 33 Magnetic disc .......................................................................................................................................... 33 shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ viii TYPES OF BACKUP ............................................................................................................................. 33 Complete backup .................................................................................................................................... 33 Partial backup.......................................................................................................................................... 34 User defined backup ............................................................................................................................... 34 CLOUD BACKUP .................................................................................................................................. 34 DATA LOSS PREVENTION .................................................................................................................. 34 DATA RECOVERY ............................................................................................................................... 34 Data loss can be caused by...................................................................................................................... 34 Data can be recovered from .................................................................................................................... 34 DATA RECOVERY TOOLS ................................................................................................................... 34 Disaster recovery .................................................................................................................................... 34 Disaster recovery plan............................................................................................................................. 35 Factors to consider .................................................................................................................................. 35 Creating a disaster recovery plan ............................................................................................................ 35 Document the DRP ................................................................................................................................. 35 Test the DRP ........................................................................................................................................... 35 SYSTEMS ANALSIS AND DESIGN ...................................................................................................... 36 SYSTEMS DEVELOPMENT LIFE CYCLE ............................................................................................ 36 The generic model................................................................................................................................... 36 STAGES IN THE SYSTEMS DEVELOPMENT LIFE CYCLE Abbreviation: (P.F.A.D.I.C.M.) ....... 36 PROBLEM IDENTIFICATION/ RECOGNITION/DEFINITION and Problem Solving ..................... 37 The problem solving process .................................................................................................................. 37 Data collection techniques ...................................................................................................................... 37 FEASIBILITY STUDY .......................................................................................................................... 38 SYSTEM ANALYSIS ............................................................................................................................ 39 SYSTEMS DESIGN .................................................................................................................................... 42 DEVELOPMENT AND TESTING ................................................................................................................. 44 DOCUMENTATION .................................................................................................................................. 45 SYSTEM IMPLEMENTATION .................................................................................................................... 46 shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 1 INTRODUCTION TO COMPUTER SCIENCE Definition of a computer A computer is an electronic device that operates by following instructions stored in its memory that accepts data as input, process it (processing) following specified procedures to produce results as output and store the information as storage for later use. Components of a computer Control unit Input device Arithmetic/Logic Unit Output device Memory unit Classification of Computers Super computer, mainframe, minicomputer, desktop, and portable computers Super computer A computer with great speed and memory, It can do jobs faster than other computers of its generation. Characteristics It is the largest computer It is the fastest computer It is the most expensive computer It can handle over ten thousand (10000) users at a time. It is mainly used in large scientific and research laboratories for processing speed, memory and other services which may not be available in smaller computers. Mainframe computers They are powerful computers Mainly used by government institutions and companies Used for tasks such as census, industry and consumer statistics, shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 2 The term is used to distinguish very big computers from less powerful ones. Characteristics Smaller than supercomputer Less processing speed than super computer Cheaper than super computers Can be used by hundreds of users at the same time They can be big enough to occupy an entire room Ideally used as servers in organisations Mini computers It is a computer that possesses most of the features and capabilities of a mainframe computer but smaller in size. It fills the space between a microcomputer and mainframe computer. They are mainly used as small to mid-range servers operating businesses and scientific applications. However, the term minicomputer has diminished and has merged with servers. It may also being called a mid-range computer. Characteristics Smaller than mainframe computer Mostly used by businesses to process large amounts of information such as controlling ATMs Used for inventory control in supermarkets, insurance claim processing and payroll Desktop computers A personal computer designed for regular use Personal computer pc is the common name Used at a single location. Characteristics Cheap and easy to use Small enough to fit on top of desks and are rarely moved Widely used for business, academic and home applications shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 3 HARD WARE AND SOFTWARE HARDWARE It comprises of several components that fall into two broad categories, namely, hardware and software. Hardware these are the physical components of a computer those we can see and touch. Physical components of a computer system such as input devices processing devices and output or storage devices. Categories of hardware Hardware can be categorised into input devices, output devices, processing devices, and storage devices. INPUT DEVICES Keying devices are used to enter data into a computer by typing on keys with letters, numbers, mathematical symbols and other special symbols. The most common is a QWERTY keyboard. Keyboards can also be seen on other devices such as ATMs They can be virtual or physical Pointing devices used by a user to point to a desired location on a computer Mouse, trackball, touch pad l and joysticks are all pointing devices Scanning devices they capture a copy of texts or photographs from a paper and reproduces same data on the computer Image scanners are used to transform printed images into an electronic format that can be stored (saved) in the computer. Special purpose scanner OUTPUT DEVICES •Any peripheral that receives or displays output from a computer. •Computer hardware equipment used to communicate the results of data processing carried out by a computer to the outside world Computers produce softcopy output, hardcopy output and audio output A soft copy is the unprinted digital document file A hardcopy is produced on a paper or some material that can be touched and carried for being shown to others Audio output is the ability of the computer to output sound Examples of Output Device Monitor Printer Plotter Speakers Projector Monitor •The device which displays computer output as softcopy. •The monitor displays the video and graphics information generated by the computer through the video card. •Monitors are very similar to televisions but usually display information at a much higher resolution. Monitors can display graphics, text and video. The size of a monitor is measured in inches diagonally across the screen; 15, 17, 19 and 21 inch monitors are the most common sizes. A color monitor can display from 16 to over 1 million different colors. Types of Monitor shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 4 •Cathode Ray Tube (CRT) •Liquid Crystal Display (LCD) •Light-emitting Diode Cathode Ray Tube (CRT) •Large •Heavy •Produce heat •Not expensive Liquid Crystal Display (LCD) •Less space •Lighter •Low power consumption •Expensive •Limited viewing angle Light-emitting Diode (LED) •Less space •Lighter •Very expensive •Provide higher contrast and better viewing angles than LCD monitor Printer •Printer is an external hardware device responsible for taking computer data and generating a hard copy of that data. •Printers are one of the most used peripherals on computers and are commonly used to print text, images, and photos Types of Printer Printers can be categorised into: •Impact Printer •Non-Impact Printer Impact Printer •It strikes paper and ribbon together to form a character, like a typewriter. Advantages Disadvantages •Less expensive •Can make multiple copies with multipart paper •Noisy •Print quality lower in some types •Poor graphics or none at all •Slow Daisy-wheel •Similar to a ball-head typewriter, this type of printer has a plastic or metal wheel on which the shape of each character stands out in relief. •A hammer presses the wheel against a ribbon, which in turn makes an ink stain in the shape of the character on the paper. •Daisy-wheel printers produce letter-quality print but cannot print graphics. Dot-Matrix •Creates characters by striking pins against an ink ribbon. •Each pin makes a dot, and combinations of dots form characters and illustrate shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ Non-Impact Printer •It uses ink spray, toner powder or inkless Advantages •Quiet •Can handle graphics and often a wider variety of fonts than impact printers •Fast 5 Disadvantages •More expensive •Occupies a lot of space •The cost of maintaining it is high Multifunction Printer (Toner-based) •An MFP is an office machine which incorporates the functionality of multiple devices in one. •A typical MFP may act as a combination of some or all of the following devices: –Printer –Scanner –Photocopier –Fax Ink-jet Printer •Inkjet printer operates by propelling variably-sized droplets of liquid or molten material (ink) onto almost any sized page. •They are the most common type of computer printer used by consumers. Thermal Printer (Inkless) •Thermal printers work by selectively heating regions of special heat-sensitive paper. •These printers are commonly used in calculators and fax machines; and although they are inexpensive and print relatively fast, they produce low resolution print jobs. Printing Speed The printing speed is measured in: cps (characters per second) lpm (lines per minute) ppm (pages per minute) Plotter The plotter is a computer printer for printing vector graphics Plotters are used in applications such as computer-aided design such as diagrams, layouts, specification sheets and banners The plotter is capable of producing color drawings in a matter of minutes Plotters differ from printers in that they draw lines using a pen Plotters are considerably more expensive than printers Speakers A hardware device connected to a computer's sound card that outputs sounds generated by the computer. Speakers can be used for various sounds meant to alert the user, as well as music and spoken text Headphones Headphones give sound output from the computer. They are similar to speakers, except they are worn on the ears so only one person can hear the output at a time. Projector An output device that can be directly plugged to a computer system for projecting information from a computer on to a large screen Useful for making presentations to a group of people with direct use of a computer shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 6 Full-fledged multimedia presentation with audio, video, image, and animation can be prepared and made using this facility An output device that can take the display of a computer screen and project a large version of it onto a flat surface. Projectors are often used in meetings and presentations so that everyone in the room can view the presentation. Types of projector •Cathode Ray Tube (CRT) projector •Liquid Crystal Display (LCD) projector •Digital Light Processing (DLP) projector STORAGE DEVICES A storage device is any computing hardware that is used for storing, porting and extracting data files and objects. It can hold and store information both temporarily and permanently, and can be internal or external to a computer, server or any similar computing device. A storage device may also be known as a storage medium or storage media. Storage devices keep information for later use Information is stored by the computer on storage media Examples of storage media Hard drive, floppy disk, compact disk (cd), zips drive, memory cards, memory stick and magnetic tape drive and online storage. HARD DISK it is found in system unit •hard disk drive is the main, and usually largest, data storage device in a computer. •it can store anywhere from160gigabytes to 2terabytes. •hard disk speed is the speed at which content can be read and written on a hard disk. COMPACT DISC (CD) Compact disk is a storage device which keeps information and music Played on computer, DVD player or a radio some cds are read only( CD -ROM)-data can only be once i.e. once the pits are burnt on to the surface ,that part of the disc cannot be used again for storage although it can be replayed endless times. Some are rewritable (CD-R) - this means you can save the data over and over again ADVANTAGES OF CDS small and portable very cheap to produce DISADVANTAGES OF CDS fairly fragile, easy to scratch very cheap to produce smaller storage capacity than hard drive or dvd needs to be protected from heat DIGITAL VERSATILE DISC (DVD) A disc capable of storing large amounts of data on one disc the size of a standard compact disc. Today they are widely used for storing and viewing movies and other data. A DVD is capable of holding any data and are most often used to store movie data, games, and install data for programs. Can be easily break Store very large capacity of data shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 7 They are also cheap Sound and picture quality is good and why they used to store films Easily break like cd WHAT IS THE DIFFERENCE BETWEEN A DVD AND A CD? Physically, a DVD and cd look the same both discs are the same size and typically have one side with a label and the other side that the laser reads, unless it is a double-sided DVD. However, the technology that makes up a DVD allows for the same size disc to hold a lot more data than a cd. MEMORY CARD Flash memory cards are small storage devices that are used to store the data backups such as the text , the pictures , audio, and video , They are more compact and portable than CDs or DVD , And they can hold more data than a CD , many gigabyte a storage media which stores memory These are commonly used in portable electronic devices, such as digital cameras, mobile phones, laptop computers, tablets, mp3 players and video game consoles. memory cards are solid state media , They are free from mechanical difficulties or damages , They are small , light and compact with high storage capacity , And they require less amount of power . DISADVANTAGES OF MEMORY CARDS Memory Cards can break easily , They can be lost , misplaced or smashed easily , They can be affected by the electronic corruption , and they make the entire card unreadable , They are more expensive than CD or DVD , The metal part can be snapped off or damaged if they are handled roughly . USB MEMORY STICK Solid way of storing data Most USB flash drives are removable and rewritable Physically, they are small, durable and reliable. The larger their storage space, the faster they tend to operate Mistakenly referred as to usb FLOPPY DISK a flexible removable magnetic disk, typically encased in hard plastic, used for storing data not commonly used nowadays available in 3.5 inches floppy 5.25 inches floppy 8 inches floppy Advantages: 1) Floppies are cheap and can be used many times 2) Floppies are easy to transport and handle Disadvantages: 1) Floppies don’t have much storage capacity 2) Floppies can get affected by heat 3) They have to handle more carefully MAGNETIC TAPES Definition - What does Magnetic Tape mean? Magnetic tape is a type of physical storage media for different kinds of data Magnetic tape is one of the oldest technologies for electronic data storage. Advantages A single magnetic tape cartridge can store large amounts of data up to 1 Terabyte. Large cartridges are used by big companies and institutions that require continuous recording and backup of data. Data collection can go on without interruption overnight or for an entire weekend. Magnetic tape can be recorded over and reused repeatedly. Large amounts of information are stored. Magnetic tape is inexpensive and budget friendly. shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 8 Disadvantages Special equipment must be purchased and set up for recording and storing data. The data can only be read on the special equipment. If the data is stored near a strong magnetic field or a large speaker, the tape can be damaged. Magnetic tape has a lifespan of 15 years. Data quality gradually erodes over time. It is necessary to keep older tape equipment just to be able to read the stored data. CLOUD STORAGE Cloud storage means the Storage of data online in the cloud, “Wherein data is stored in and accessible from multiple distributed and connected resources that comprise a cloud. Cloud storage can provide the benefits of greater accessibility and reliability; rapid deployment; strong protection for data backup, archival and disaster recovery purposes EXAMPLES: Google drive flicker Microsoft skydive drop box Application of hardware devices Point of sale (POS) terminal Electronic device used to process electronic payments at retail locations. May work together with a bar code reader to determine if item names and prices. Generally has its core a personal computer, which is provided with application specific programs and I/O (input and output) devices for the particular environment in which it will serve POS in a restaurant is likely to have all menu stored in a database that is accessed to retrieve information to do with prices of food items and others. It typically does the following Reads item name and price Reads the information on customer's credit or debit card. Transfer funds from customer account to the sellers account ( if the card has sufficient funds, otherwise reject the transaction). Records the transaction and prints a receipt. Regardless of the software used, every POS should at least have the hardware below: a) Register screen A standard monitor that displays the product database The device also enables other functions such as employee clock in and viewing sales reports. b) Barcode scanner Scanning barcodes pull out product information (name and price) from the database and adds it to receipt total. Barcodes may be interested with inventory or stock management systems to automatically adjust stock levels when an item is scanned. c) Receipt printer Prints customer receipt d) Card reader Enables the POS to facilitate electronic payments made by debit or credit card Automated Teller Machine (ATM) Is an automatic banking machine that allows bank customers to bank customers to access their accounts without any help from a bank teller Customers have a magnetically encoded plastic card and a pin(Personal identification number) to perform ATM transactions They can perform the following on an � Withdraw cash Pay bills shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 9 Make deposits Obtain statements Effect bank transfers Components of an ATM a) Input device Card reader An input device that reads data from a card when inserted into the machine Card reader is part of the identification of you particular account number and the magnetic strip on the backside of the ATM card is used for connection with the card reader. The card once swiped or pressed on the card reader or inserted in the card reader which captures your account information. Data from the card is passed on the host processor server. The host processor, thus, uses this data to get information to get the information from the card holder. Keypad The keypad enables the ATM user to enter their PIN or amount they would like to withdraw. It also has an enter key that communicates whether to approve the requested transaction and delete and cancel facility that cancels any transaction. Some keypads are touch screens. b) Output devices Speaker Most advanced � s has a speaker facility that provides audio feedback when a particular key is pressed. This of benefit to the blind as they can do their banking without any help Display screen Displays the transaction information Each step of withdrawal is shown by the display screen. Leased line machines commonly use monochrome or colour crt (cathode ray tube). Dial up machines use a monochrome or LCD (liquid crystal display) for their screens. Receipt printer Prints all the details of transactions such as date and time, the amount withdrawn and balance of your account Cash dispenser: Central system of the ATM machine where the required money is obtained Counts each note and give the required amount. This action is carried out by Hy prediction sensors. A complete record of each transaction is kept by the ATM with the help of a Real time clock (RTC) device. Data capturing systems An electronic data capture (EDC) system is a computerized system designed for the collection of data in electronic format. EDC solutions are widely adopted by pharmaceutical companies and contract research organisations (CRO). Some of the most fundamental EDC functionalities comprise of quality checking of already collected data, allowing researchers to enter data into a centralized database and forming web- based data entry forms. Typically, EDC systems provide: A graphical user interface component for data entry. A validation component to check user data. A reporting tool for analysis of the collected data. Examples of Electronic Data Capture systems include: Medrido Castor EDC Aetiol Datalabs Poimapper Advantages of EDC Allows logic checks to highlight discrepancies to site during data entry. shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 10 Data can be reported in real-time, ensuring safety data are readily available for central review, advantageous for high risk- risk trials. Queries can be sent instantly with reduced turnaround times for data clarification. Using EDC reduces paper management time require less physical storage space. Disadvantages of EDC Specific training is required and site staff needs to be encouraged to submit data immediately following participants visits, instead of batching data entry. Database user access and internet browser compatibility monitoring systems are required to ensure only current site staff have access and are using a supported browser. SOFTWARE Software can be defined as the programs/instructions that make the hardware to work. Set of programs that contains instructions that tell the computer what to do and how to perform each task. Classes of software They are two classes Systems Software and Application Software APPLICATION SOFTWARE Refers to programs that enable the user to achieve specific objectives e.g. creating documents, spread sheets, designing. It is classified in to categories General purpose software Special purpose software General purpose software Software that performs general tasks Tasks that can be done by anyone regardless of their profession or area of specialisation. In this category belongs the following: Word processing software e.g. Microsoft (Ms) word. Spreadsheets e.g. Microsoft (Ms) Excel Database Management Software e.g. (Ms) access Presentation graphics e.g. Microsoft (MS) power point Dtp Desktop Publishing e.g. Microsoft (Ms) publisher Special purpose software Refers to application software that is meant for use by professionals in specific industry like mining, hospitality, transport, agriculture, banking and insurance, retail and medical. NB Take note people in these areas need general purpose software to perform certain tasks such as word processing or presentation. Programs dedicated to very specific functions within a knowledge area of profession such as accounting, engineering, manufacturing, transport and logistics, statistics There are two ways of acquiring software Off the shelf software Customized software Off the shelf software Ready-made software that you purchase .e.g. Microsoft Office Characteristics of off the shelf software Sold in stores can be sold on the Internet. shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 11 Installation can be standard or custom. Can be purchased, installed and used immediately. Written to solve specific problem. Can be designed to do one particular task e.g. payroll, stock control Advantages Less expensive than custom written because of economies of scale Readily available since it can be bought from a shop or the internet and installed right away. Large user base that is available in the form of advice forums, 3rd party books and training courses. In addition staff may be already be familiar with software. Software is tried and tested therefore there are fewer bugs than newly written software Runs on a wide range of hardware Disadvantages Ownership can be high due to license and upgrades. Software may not completely fit the task since it would have been developed for a wide range of customers. Software may have too many additional unwanted extras. Customised software Specifically developed for some specific organisation or user. Also known as tailor made software. Also known as bespoke software. Characteristics Takes a lot to time to write and test since requirements would be unique. Designed and written specifically for one company. Advantages Designed to do exactly what the user wants. Can be written to run on user-specified hardware. Can be interested with existing software. Disadvantages Time consuming to have it developed Expensive since the one customer has to pay for all expenses. There are no economies of scale. There is limited support since nobody else would be using that software. 3rd part books not likely to be available. New staff unlikely to be familiar with software. Systems software A group of programs (software) that is almost always sold together with the computer. It helps you manage and control the hardware of your computer system. . SYSTEMS SOFTWARE Refers to a group of programs (software) almost always sold together with the computer. In other words, it helps you manage and control the hardware of your computer. It also provides an interface between you and the computer. To every computer software for it to be able to run Operating System (OS) is a part of systems software that provides a communication medium between application software and computer hardware. E.g. Windows 10, Linux, MacOs desktop computers and laptops, while Android for smartphones. Utility software these are programs that are used to manage computer system effectively. Language translators are also known as Systems Development software. These are programs used to develop software (system and application software). System Development software is also referred to as programming languages. A programming language is a language used to write software and understood by computers. Examples are Java, Visual Basic, Python and C etc. Programming language understood by computers that is used to write software. Programming is the process of writing (developing) computer instructions (software). shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 12 Programmer is the one who develops computer software. Examples include java, visual basic, python C, C#, java script, html, php etc. It can be divided into three categories namely Operating system Utilities Language translators Operating System Is the part of systems software that provides a communication medium between application software and computer hardware. It ensures connectivity between hardware of computers and the application software Examples are Windows 10, android, Linux, and apple iOS etc. Operating systems Operating System and utility software belong to the category of systems software. Though different Operating systems are available for computers performing similar functions. Most of these functions are performed automatically in the background, often without the users’ awareness. Basic minimum software that a computer needs for it to function. Provides a user interface that allows that allows one to work with the computer. Manage all the hardware resources Provides a platform for managing files and application programs. Functions of operating system Manages the computer resources, such as the CPU, memory, disk drives, and printers. Provides the foundation for application software to be launched. Establishes a user interface Determines the to types of application software that can be installed. Coordinates the applications running on the computer at any given time. Reports errors such as printer out of paper, software error etc. Executes and provides services for application software. Manages the computer’s memory and processes, it is sometimes referred to as a task manager. Also called a device manager because it controls how input and output devices (hardware) function on a computer system. Allows the user to communicate with the computer. It is an interface between the user and the computer Below are more functions of an operating system: 1) Routes data between the hardware resources and the application programs. It provides device drivers or refers the user to install a specific driver. 2) Booting/ starting the computer Starts the user interface and properly shuts down the hardware. Instructions for booting are stored on the Basic input output system (BIOS) chip that resides on the motherboard. They are two basic ways of starting a computer cold boot and warm boot. Cold boot refers to turning on a computer that has been shut down. Warm boot refers to starting a computer without turning of power. A proper shutdown command is recommended so that programs and files are properly closed. During booting depending type of os a message is displayed on the screen. Upon completion of booting the user interface or the login screen will display. 3) Providing a user interface. User interface (UI) refers to the means which you interact with the computer. shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 4) 5) 6) 7) 13 They are two types of interfaces, namely graphical user interface and command line interface. A GUI presents visual images such as buttons, tiles or icons that you tap or click to tell the OS what you want to do whilst a CLI requires that you type commands onto a prompt such as c:\users\firstname using a keyboard Network specialists will sometimes use a CLI to configure or troubleshoot a network device. Managing application programs and coordinating the flow of data. Manages the installed programs and allows you to run, install and uninstall programs. It provides a task manager thereby it manages computer resources. It allocates data to and software to or from the CPU as needed. Manages the CPU, cache memory, Ram, input, output devices. Configuring hardware and peripheral devices. Configures all devices that are installed or connected to the computer. Each device requires specific software known as driver software for it to properly function on a computer. Examples are printer drivers, sound drivers etc. Normally drivers are supplied by manufacturers and usually come as a CD. In some cases operating systems already provides some of the drivers. Plug and play refers to a situation where the driver is readily available. Providing a file system Keeps track of files stored on the computer. Provides tools for managing files. Copying, renaming, moving or deleting. Utility programs restore, clean up, search, defragment storage devices and back up files are included in the OS package. Software updates and security. If permitted it automatically downloads available updates It provides program fixes, security enhancement and updates of device drivers Types of operating systems They are several categories of Operating systems that are used in the field of computing. One way is by considering if they are used on networks or not. Based on this classification we have. a) Standalone Operating systems Is the one that works on a desktop? Provides its services to just one computer at a time. Examples: windows 10 home, windows 7 enterprise. b) Network Operating Systems (network OS or NOS) Designed to support computers and peripherals devices connected in a network Enable sharing the sharing of data files, application programs and other services such as printing, over a Local Area network (LAN) Example: windows 2000 server, UNIX, NetWare, Linux and Windows .net etc. etc. c) Embedded Operating Systems Designed for embedded systems. Embedded systems are specially designed computers that are found inside other gadgets or equipment. Examples of embedded systems are mobile phones, washing machines, microwave oven, ATM and digital camera to mention a few. Examples of embedded operating systems are: palm os, Android OS, Windows CE, iOS, Symbian, pocket PC 2002. Personal computer operating system It depends on the hardware because some hardware is designed for specifically for a particular OS. Mac books and apple computers are compatible with mac OS The OS should be compatible with the hardware in terms of in terms of data bus size. shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 14 A 64 bit OS cannot be installed on a computer less than 64 bit. Utilities Software programs that are used for effectively managing a computer system. They can be referred to as housekeeping tools. Programs which improve the functioning of the operating system or supply missing or additional functionality. They perform the following tasks. Backing up files. Compress files e.g WinRAR, WinZip, power iso. Decreasing the size of files, resulting in faster downloads. Searching for and managing files. File management functions such as: copy files; determine how and where files are stored and delete files. Search utility. To Providing antivirus software protection - antivirus software protects the computer from viruses. Examples: are bit Defender, Kaspersky, Norton and set nod32 antivirus. Help utility. Language translators A Translator is a program that translates a source program/code into an equivalent object code [machine code] before the program is executed by the computer. System development software fall under this category. Used to develop software (systems and application software). HARDWARE and SOFTWARE MAINTENANCE A computer is functional if hardware and software are working properly computers just like any other machines sometimes get faulty and fail to function This means either hardware or software can malfunction. Relationship between hardware and software Hardware and software are mutually depended on each other Hardware without a set of instructions cannot be utilized hence it’s of no value Software can also not be utilized without supporting hardware In order for proper functionality of the computer relevant software should be installed on to the appropriate hardware Every device of hardware requires a device driver so it can function properly Device Driver Program(software) that controls a particular type of device that is attached to your computer Troubleshooting A systematic approach to problem solving that is often used to find and correct faults with computer systems The first step is to gather enough information on the issue, such as undesired behavior or lack of expected functionality shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 15 COMPUTER NETWORKS AND INTERNET TECHNOLOGIES Computer networks Refers to a collection of computers and other devices connected together in order to communicate. A network can be as small as just two devices connected or as big as millions or more computers connected. Networks can be wired or wireless. Reasons for networking Sharing information Sharing resources (such as printers) Sharing communication such as receiving and sending emails. Networks can be wireless or wired, depending on the medium of communication. Expensive peripherals like printers and scanners can be shared between users. Messages can be sent easily and faster between users whether on WAN or LAN. Avoids duplication of information as users can access the same file on the network Network software can be purchased cheaply than buying individual packages for each computer. It is possible to access data or programs from any terminal or workstation. Data and programs can be stored centrally making it easier to maintain and backup. Users can be easily prevented from accessing files not intended for them. Allows sharing of files, software and data held in computers Allows emails to be send between users Advantages of Networking Disadvantages of Networking Sophisticated equipment is needed, which may be expensive to buy. Security of data can be a problem due to hacking. Wiring can be expensive both to buy and to install; wiring can be sunk on the ground to avoid trailing cables. If a server breaks down, the whole network becomes unusable. Networks need experienced network managers, who will be highly paid to keep the network running Network architectures Client a computer that requires service from another computer on a network Server a computer that processes the request and sends back a response Network: A connection of computers for them to share data, files and resources like a printer the client. Host a computer connected to a network of computers. Data communication: The process of transferring data through networked computers Some networks have specific computers designed as servers, while others do not. In a network where no specific computers designed as a server, every computer can assume the role of a server or client depending on whether it is requesting a service or processing a received request or processing a received request to fulfill it, respectively. Peer to peer network A network that does not have designated services. Client/Server Is a network that does not have designated server shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 16 Classification of networks It is often based on the hardware and software technologies used to interconnect the computers and the geographical coverage. -Computer networks are grouped into Local Area Networks (LAN) and Wide Area Networks (WAN). -However we also have WLAN (Wireless Local Area Networks), MAN (Metropolitan Area Networks) and PAN (Personal Area Networks); and these are described below. Classes of Networks LANS and WANS Local area network Covers a small geographical area Examples: office, house, classroom, lab hotel, university or school. Covers a small geographic area Pan can be as small as a phone connected to a laptop to share files. Pan and can Wide area network A computer network that covers a broad geographical area Any computer network whose communication links span city, town/metropolitan, regional or national boundaries NB bank network The largest WAN covers the world. Man metropolitan area network Spans across city or town Network topologies Topology refers to the arrangement or layout pattern of computers and other devices in a computer network Also called network architecture It can be physical or logical They are named on how computers are arranged in that network Devices on a network are called nodes or hosts Nodes includes VOIP ( voice over internet protocol) phones, computers and peripheral devices like printers Topologies include Star, Ring, Bus, Mash Bus topology: A network topology in which each workstation is connected to a main cable (backbone) through which the network is established. The Backbone acts as the common medium; any signals sent or received go through the backbone in order to reach the recipient. Star topology: A network topology in which each workstation is connected to a central node/connection point through which the network s established The central node (hub) re-directs and directs the packets according to the data traffic and their recipient. Ring network topology Computers are connected together to form a circle and uses a token when transferring data. Data/information travels in one direction only. Information moves around the ring in sequence from its source to its destination. shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 17 As data passes from one computer to another in the ring, each computer removes any data relevant to it and adds any data it wishes to send. The diagram below illustrates the physical configuration of a ring network: Advantages of Ring Network Data processing is faster as each computer processes its own processor. Has very high data transfer rates. Uses a token to avoid data collision or loss It is possible to create large networks using this topology If one computer breaks down, others will remain working as they have their own processors and storage facilities. Performs better than star network when traffic is very heavy Disadvantages of Ring Network If one computer breaks down, the whole network is disrupted. a faulty connection between two stations can cause network failure Its requirements are expensive, that is buying several computers with processors and storage facilities. It is difficult to link the computers together. Difficult to add another computer without disrupting the networking Only the computer with the token is allowed to send data at a given time. One may not send data when another node (computer) is still sending its own data. System is less secure as token together with data has to pass through other nodes that do not concern it. Mesh Network A network in which each computer serves as a relay point for directly sending information to any other computer on the network No central device oversees a mesh network, and no set route is used to pass data back and forth between computers. Thus, if any one computer is damaged or temporarily unavailable, information is dynamically rerouted to other computers—a process known as self-healing Advantages of Mesh Network If one computer breaks down, others will remain functional. If one computer breaks down, the network is not disturbed. Computers have their own storage and processing capabilities. Expensive to buy computers with their storage and processing facilities Too much cabling is involved, which may be expensive. Disadvantages of Mesh Network INTERNET SERVICES These include email, e-commerce, e-learning and social media Email Long back mail was sent by post Short for electronic mail Used to send electronic messages over the internet It real time meaning the message is delivered there and then Examples of companies that that offer email services Gmail, yahoo, cool toad and many more E-commerce The buying and selling through the internet It does not have geographical limitations shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 18 You can buy and sell in the comfort of your home Payments can be done virtually or online using credit cards master cards, mobile money transfer or you have to visit the bank Advantages of e-commerce Buying and selling is 24hr a day and 7 days a week (24/7) Eliminates travelling costs to make a purchase No time wasted in queues Transactions can be done by several people simultaneously Reduces the risk of moving around with cash E-learning The short for electronic learning Also referred to as online learning, computer mediated learning, web based learning, and technology mediated learning or virtual learning A computer based learning and teaching system that enables people to learn from anywhere at any time. Learning conducted via the internet or any other electronic media You can learn anywhere from anywhere Examples websites, social media platforms YouTube Advantages of e-learning You learn from anywhere at any time You can self-pace your learning depending on learner speed and commitment It can be interactive, engaging and effective It reduces cost of learning It is flexible in terms of time tables Learning can be fun for example gaming Social media Refers to internet based applications and tools that facilitate the creation of tools that facilitate the creation and sharing of information, ideas and other forms of expression among people and communities Members who participate in a particular social network form a virtual community While it presents seems to emphasize on defining social interactions it is being used for other purposes like marketing, learning and many more. DATA TRANSMISSION Is the process of transmitting or transferring data between two or more digital devices connected on a network? It allows devices to communicate with each other During communication, computer data is transmitted between e sending and receiving computers. The mechanism is called data transmission modes They are three modes of data transmission. They are three modes of data transmission Data transmission modes Full duplex/Duplex Simultaneous transmission of data in both directions It is both bidirectional and simultaneous The channel can transmit data signals in both directions on one signal carrier simultaneously One example is a mobile phone High transmission speed Improved communication efficiency due to simultaneous sending and receiving of data signals. Advantages of Duplex shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 19 Half Duplex transmission modes Sending and receiving of data is bidirectional but not simultaneous. When the other end is receiving the other end should be transmitting Example walkie talkie Cheaper to extend over long distances Since data is transferred over a single wire Fewer wires are required when extending it. Though they is need for electric components the electric components are cheaper There is no wire timing problems caused by different wire lengths. Unlike in parallel It is cheaper than full duplex since it uses one channel for both sending and receiving. The flow of data is unidirectional Common example is a radio station Radio stations send signal to their audiences but never receive signals from them thus the data transmission is one directional In computer networks it is common on fiber optic communication One strand is designed for sending signals only and the other one for receiving signals Entire bandwidth can be used during transmission Cheaper in hardware since there is no need for receiving channel but sending only. Advantages of Half Duplex Transmission Simplex transmission Advantages Data transmission media It is the pathway through which data is transmitted or carried between the sender and the receiver (medium in singular and media in plural). Normally data is transferred in electromagnetic signals Electric signals are in the form of electric current whilst electromagnetic signals are a series of electromagnetic energy pulses at various frequencies. Transmission media can also be referred to as communication media. It is classified in to two bounded and unbounded media Bounded media are also called guided or wired whilst unbounded are also known as unguided or wireless Bounded media Any data transmission medial that confines data signals to a specific path using a wire cable. It is therefore referred to as wired medium Any data using wire or cable, it is therefore referred to as wired medium. Data signals traversing bounded media are directed and contained by the physical limits of transmission media Examples Fibre optic cable Coaxial cable Twisted pair cable Twisted pair cable Copper wires are cheaper and are of good performance hence they are commonly used. However, they are susceptible to signal interference if at least two wires are lying together. The signal interference is known as electromagnetic interference and may result in distortion of communication To reduce the electromagnetic interference in copper cables, pairs of of copper wires are twisted together, hence the name twisted pair cables Ethernet cable is an example shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 20 Characteristics of twisted pair cables It is relatively cheaper It has low noise immunity It can be affected by external magnetic interference It has the lowest bandwidth compared to coaxial and fibre optic cables Maximum cable length between hub and computer is 100m It is an insulated copper wire with mesh wire shielding and insulating cover. May be reoffered to as coax It has high capacitance, meaning it has good signal propagation It has low magnetic interference (low noise), it is bulky and stiff to bend. It has higher immunity to noise than twisted pair. It is less affected by external magnetic field It is more expensive than twisted pair cable but less expensive than fibre optic cable. It has higher bandwidth than a twisted pair cable but lower than a fibre optic cable The maximum cable length between hub and computer is 500m It is similar in construction to the coaxial cable but it is faster and more expensive It has a narrow strand of glass core, plastic buffer, Kevlar cushion and plastic shield. It has a very high transmission speed and very high capacity. it is highly immune to noise since it is not affected by electrical noise It is not affected by electromagnetic interference. it is the most expensive compared to twisted pair and coaxial cables it has a very high bandwidth maximum cable length 80km Coaxial cable Characteristics Fibre optic cable Fibre optic cable characteristics Unbounded transmission media Data signals flow through the air. Oftenly referred to as wireless transmission. Data signals are not guided or bounded by a physical channel to flow Therefore are three types: Radio transmission, microwave transmission , and satellite transmission It is the sending of data signals through air by modulating electromagnetic wave frequencies below usable light .It carries data signals over relatively long distances. Radio frequency (RF) waves are relatively easier to generate They travel long distance unlike microwave RF can easily penetrate building s .They can travel in an direction from the source , thus there no need for careful physical aligning of transmitter and receiver They are prone to interference from electrical equipment. Behavior of RF waves is dependent upon frequencies. They tend to travel in straight lines and bounce off obstacles when frequencies are high, whereas they pass through obstacles at low frequencies are high, whereas they pass through obstacles at low frequencies very well Radio transmission Characteristics of radio frequency transmission shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 21 Microwave transmission Refers to a straight line of sight transmission since transmitting station and sending station must be in visible contact. This places a distance limit of about 50km between sending and receiving stations The range of operation is between 3 GHz and 10 GHz. These high operating frequencies allow microwave transmission to carry a large quantities because of their bandwidth As distance between sending and receiving channel's increases, signal strength reduces. Repeater stations must be installed to revitalize the signals Satellite transmission Uses electromagnetic waves as carrier signals to transmit data between ground and space vice versa An unobstructed line of sight between the orbiting satellite and a station on earth is required for satellite transmission Although they travel in straight line they are not affected by such factors such as the Earth's curvature as in the case of ground-based wireless transmission. Internet service providers ISP stand for internet service provider It's a requirement to connect to the internet It is a company that allows its clients to connect to the internet They are also known as IAP internet access provider Examples net one econet and powertel etc. etc. Services offered by ISPs Act as an interface between customer computer system and the internet. This is usually done through dial up services, DSL digital subscriber line service and cellular data service Provides a direct link between organisation network and the internet Provides service such as electronic mail email, web hosting and also designing Connect clients to the nearest internet gateway. Provide modem for dial up connections Provide security to their clients. It is archived by stopping spread of viruses and malware by applying antivirus systems for their clients Mobile technologies Refers to � battery powered information and communication technology Mobile technologies includes both software and hardware They include smartphones, satellite, PDAs personal digital assistants, tablets and laptops Mobile phone A portable handheld wireless phone that uses a cellular radio system over a wide area They are categorised into two. Feature phones and smartphones It is limited in functionality. Primarily allows one to make calls and send text messages and generally does not allow users to connect to the internet Feature phone Smartphones Has more functionality than a feature phone Runs software and applications which cannot run on a feature phone Refers to a wireless communication technology used to transfer signals between the transmitter and receiver by using satellites They are used for radio broadcasting in mobile communication Satellite communication shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 22 PDA Personal digital assistant Also called a hand held personal computer and functions more like a personal information manager It combines features, including computing, telephone/fax, internet and networking. It can be used as a mobile phone, personal organiser, web browser and � fax sender It is a touch screen, a wireless, mobile device smaller than a laptop but larger than a smartphone. It is called a tablet PC, though commonly shortened to just tablet. One can virtually everything that one can do on a PC Are used in almost every facet of daily life. It is applied virtually in all most all sectors you may think of Refers to electronic devices that communicate through the air using radio frequency signals. In wireless technology communication takes places without cables. Mobile technology hinge on wireless technology which provide greater mobility. Some wireless technologies covers a short distance whilst others cover long distances Mobile technologies help in communication Provide easy access to agricultural and market information. Provides e banking ecommerce e insurance to farmers Examples include Eco farmer, farmers club Telecel and Murimi Umlimi Rubiem tech E agriculture or e farming are a result of the applications of mobile technology in agriculture Refers to the exchange (transmission or conveyance) of information between two or more people by whatever means, such as writing, talking or any other means. Wireless technologies are widely used in communication. Whatsapp, Facebook, calls and texts are used every day globally Used for recording playing and editing music and videos People can also buy and sell their services on the internet Tablet Application of mobile technologies Agriculture Communication Entertainment Education Mobile learning M-learning or mobile learning is a form of distance education where learners use portable devices such as mobile phones to learn anywhere at any time. The portability that mobile devices provide allow for learning anywhere, hence the word "mobile" in "mobile learning". M-learning devices include computers, MP3 players, mobile phones, and tablets. M-learning can be an important part of informal learning. M-learning is convenient in that it is accessible virtually anywhere. M-learning allows for the instant sharing of feedback and tips since the mobile devices are often connected to the internet. M-learning also brings strong portability by replacing books and notes with small devices filled with tailored learning contents. M-learning has the added benefit of being cost-effective, as the price of digital content on tablets is falling sharply compared to traditional media (books, CDs, DVDs, etc.). It offers some possibilities, such as greater and different access to information. It also offers transcendent innovations, such as the increase of informal and playful activities, iconic virtual membership, and networks of friendly interaction within new scales of values *Here's some stuff you might want to know* How does mobile technology help with education? Mobile devices allow students to connect, communicate, collaborate, and create using rich digital resources. Learning to be comfortable with such devices prepares students for shifts in the global economy and helps them adapt to quickly evolving new technologies. What is an educational mobile application? Any mobile software that can be a remote learning platform is called an educational app. This integrated learning system offers complete knowledge and end-to-end learning solutions. shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 23 What is mobile technology in the classroom? Mobile learning seeks to utilize the ubiquity and unique capabilities of mobile devices to make course materials available to students wherever they are, and to create new kinds of learning experiences that help students engage with course content and the world Mobile shopping M shopping refers to the buying and selling goods and services through mobile (handheld) devices such as laptops, tablets and smartphones You can buy and sell virtually anything in the comfort of your home, hostel, office or car. Advantages You can shop online at any time, from anywhere. Whether you're sitting at home on the couch or waiting for a bus, you can easily browse products and make purchases with just a few taps on your phone Eliminating the risk of moving around with cash since payment is done remotely and digitally using plastic money in most instances Saves on travelling and subsistence costs and time. It is convenient Mobile banking Use of mobile devices in banking Banking is no longer confined to the banking walls and working hours of the banking staff. Mobile marketing A digital marketing strategy where audiences are reached via emails, social media, texts messages and applications such as Pindula Advantages of mobile marketing Huge audience can be reached Cheaper since they is less paper work and can be done online Modern society spends much of its time on mobile devices Disadvantages Scams Pop up messages adds they irritate internet users Wireless technologies WiFi Some texts write it as Wi-Fi Wi-Fi is an acronym. It short for wireless fidelity The technical name is IEEE802.11 It’s a universal wireless technology that uses wireless technology that uses radio frequencies to transfer data and allow high speed internet connections without using cables It operates in an unlicensed 2.4 radio bands with 11Mbps (802.11b) or 54Mbps (802.11a) data rates respectively. Mbps is short for megabits per second. A Wi-Fi enabled device is needed to be able to connect to a Wi-Fi Stands for worldwide interoperability for microwave access A wireless broadband communication technology that is based on the IEEE 802.11 standards It eliminates the need for wires by ISPs to provide internet connectivity to its clients They do it wirelessly by providing base stations Unlike WiFi which is local area network, WiMax is for wide area network Its speed can get unto gigabits per second It can run on both licensed and unlicensed spectrum whereas WiFi only runs on unlicensed spectrum WiMax shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 24 Bluetooth It is a short range wireless communication technology Commonly used share files and connect to audio devices A network of devices connected to a Bluetooth is called a mobile ad hoc network (MANET). The network is self-configuring and infrastructure-less Infrared It is abbreviated IR, a wireless short range communication technology It is line of sight mobile communication technology Line of sight refers to a communication technology that requires the transmitter and receiver to be in visible contact for communication to take place It cannot penetrate through wall or other obstacles Microwave Refers to line of sight transmission since the transmitting station and receiving station should be in visible contact It places a distance limit of 50km between the sending and receiving station As distance between sending and receiving station increases, signal strength reduces Communication protocols A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchronization of communication and possible error recovery methods. Protocols may be implemented by hardware, software, or a combination of both. Communicating systems use well-defined formats for exchanging various messages. Each message has an exact meaning intended to elicit a response from a range of possible responses predetermined for that particular situation. The specified behavior is typically independent of how it is to be implemented. Communication protocols have to be agreed upon by the parties involved. To reach an agreement, a protocol may be developed into a technical standard. A programming language describes the same for computations, so there is a close analogy between protocols and programming languages: protocols are to communication what programming languages are to computations. An alternate formulation states that protocols are to communication what algorithms are to computation. Multiple protocols often describe different aspects of a single communication. A group of protocols designed to work together is known as a protocol suite; when implemented in software they are a protocol stack Networking hardware Networking hardware, also known as network equipment or computer networking devices, are electronic devices which are required for communication and interaction between devices on a computer network. Specifically, they mediate data transmission in a computer network. Is defined as the hardware and/or software whose primary purpose is to route and control communications between computers or computer networks. Examples of network devices include but are not limited to, routers, firewalls and network load balancers. 7 main devices that are used to build a network Router, Network cards, Cable, Hub, Bridge, Switch, and Modem. Seven main devices used to build a network are as follows Network interface card A network interface controller (NIC, also known as a network interface card, network adapter, LAN adapter or physical network interface and by similar terms) is a computer hardware component that connects a computer to a computer network. Early network interface controllers were commonly implemented on expansion cards that plugged into a computer bus. The low cost and ubiquity of the Ethernet standard means that most newer computers have a network interface built into the motherboard, or is contained into a USB-connected dongle. shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 25 Computers use parallel data transmission technology for internal data transfer where multiple bits (binary digits) are sent simultaneously. However the communication media use serial data transmission, in which a single data bit is sent at a time. The purpose of the NIC is to convert messages being sent for the media to be able to handle it and vice versa for the computer to be able to understand it. A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by modulating one or more carrier wave signals to encode digital information, while the receiver demodulates the signal to recreate the original digital information. The goal is to produce a signal that can be transmitted easily and decoded reliably. Modems can be used with almost any means of transmitting analog signals, from light-emitting diodes to radio. Modem Switch A network switch (also called switching hub, bridging hub, and, by the IEEE, MAC bridge) is networking hardware that connects devices on a computer network by using packet switching to receive and forward data to the destination device. A network switch is a multiport network bridge that uses MAC addresses to forward data at the data link layer (layer 2) of the OSI model. Some switches can also forward data at the network layer (layer 3) by additionally incorporating routing functionality. Such switches are commonly known as layer-3 switches or multilayer switches. Switches for Ethernet are the most common form of network switch. Ethernet switch operates at the data link layer of the OSI model and has multiple ports; hence it is used to connect multiple devices such as computers, servers, printers, IP phones, and many other Ethernet IP enabled devices. shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 26 SECURITY AND ETHICS Computer virus A program software that is designed to harm or damage the normal operations of a computer together with s it's programs and files and usually causes irreparable damage to the infected computer. A computer virus is a type of computer program that, when executed, replicates itself by modifying other computer programs and inserting its own code into those programs. If this replication succeeds, the affected areas are then said to be "infected" with a computer virus, a metaphor derived from biological viruses. Computer viruses generally require a host program. The virus writes its own code into the host program. How does it affect a computer? Like the real thing, computer viruses replicate themselves, spreading through your operating system and network. At the same time, the virus is wreaking havoc: it can damage programs, delete files, and make devastating changes to your hard drive, all of which can result in reduced performance. : it can steal data or passwords, log keystrokes, spam your email contacts corrupt files erase data, cause permanent damage to the hard disk, And sometimes can even take over your device control. How do viruses spread? Viruses used to be spread when people shared floppy disks and other portable media, now viruses are primarily spread through email messages. Unlike worms, viruses often require some sort of user action (e.g., opening an email attachment or visiting a malicious web page) to spread. How does virus spread from one computer to another? Typically, computer viruses spread through malicious online downloads, infected email attachments, or by plugging in infected hardware like an external flash drive (USB stick). Computer viruses can spread through almost any method of file sharing, as long as the virus can avoid detection by antivirus programs. Antivirus software Not opening email attachments coming from unusual people Update antiviruses regularly Avoid sharing files using removable media Avoiding downloading software from insecure sites Have back up of computer data and programs stored on an external hard drive Refers to behavior that is morally or socially acceptable Ethics are moral obligations and one cannot be taken to court for breaking such. Part of computer security that focuses on protecting computer networks and data on the internet. Methods of preventing viruses Ethics Cyber security shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 27 Cyber wellness (CW) refers to the positive well-being of Internet users. It involves an understanding of online behavior and awareness of how to protect oneself in cyberspace. The focus of CW is about helping students to become responsible digital learners. Importance of cyber wellness Limits amount of time one spends using the computer on the internet Prevents addiction to online games Limits websites that one goes to Refers to using the internet and online resources One has to stay safe while using the internet. Prioritized to stay safe on the internet Internet criminals (cyber criminals) can make you visit dangerous sites and then install viruses on your computer and steal your personal information. The address should begin with https and not http Look for a lock in the address bar It should have contact information Does not have a lock in the address bar and begins with http Check the spelling if it's correctly spelt Makes offers that are too good to be true Offers questionable content such as illegal material or pornography Lacks legitimacy, no contact information Request bank details or credit card number to verify identity Check properties of website link and see if they are genuine. Cyber use Characteristics of safe and unsafe sites Signs of a safe website Signs of an unsafe website Handling online content and behavior One should take measures from being victims of some other mischievous internet users Some of the measures Avoid using untrusted computers, secondary storage devices such as flash disks, as well as untrusted websites and networks Make sure your computer has to up to date antivirus software since viruses are most common from online attacks Never assume that every email you receive was actually sent by the person listed as the sender Avoid click on links in emails unless you requested for them Bad online content and behavior a) Inappropriate content Exposition to pornographic or illegal material Bad beliefs and political views b) Cyber bullying Cyber bullying is bullying - unwanted, repeated, aggressive, negative behavior - that takes place over digital devices like cell phones, tablets, and computers. Cyber bullying can happen over email, through texting, on social media, while gaming, on instant messaging, and through photo sharing. c) Illegal activity Selling of weapons Online gambling Suicide sites shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 28 Recipes of making bombs and drugs Online Relationships Cyber relationships Internet relationship between two people Usually they meet online and did never met physically They know each other through the internet Copyright issues Copyright The legal right given to an author of original work, to print, distribute, publish perform or film their work, for a fixed number of years. It usually expires in 50 years violating a copy right is illegal author of original work can take legal action it is good practice to cite the author of the original work Copyright infringement Refers to the use of copyrighted material e.g. book song, film without the permission of the copyright holder. Infringement includes using someone’s music to create your own video without getting permission from the owner Importance of copyrights Protects the right of the author or originator of creative work, to control the dissemination and copying of their work Unauthorized person are prevented from copying the work It prevents benefiting from copyrighted material Plagiarism and piracy Plagiarism Refers to the using someone’s work (writing or ideas) without crediting the original author and pretending that it is yours. Consequences of plagiarism a) Destroyed academic reputation b) Destroyed student reputation c) Legal charges Piracy Refers to the illegal reproduction of someone’s work Software piracy refers to0 the illegal, copying and/or distribution of copyrighted software or computer programs. Non viability of software updates High risk of virus infection Increased chances that the software will function correctly or will completely fail Consequences of piracy shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 29 Computer crime Refers to all crime committed using the computer Is the unauthorized use, access, modification and destruction of hardware, software, data or networked resources. Computer crime can be committed by anyone who uses a computer. However, hackers, disgruntled employees or customers and an organisation’s competitors usually commit a crime Examples of illegal activities i. Salami slicing skimming small amounts of money from bank accounts ii. Card cloning creating a fake credit card by stealing information iii. Denial of service computer activity that results in in legitimate users being denied access from databases iv. Social engineering tricking employees to gain access v. Dumpster driving finding private information in garbage cans/rubbish bins vi. Spoofing stealing passwords through false login page Consequences of computer crime include, but are not limited to, financial loss, increased costs for counter measures, reduced productivity in companies and job loss. Data protection measures Common data protection includes changing passwords frequently, limiting access to information to key people only, installing updated antivirus software, and backing up software and dataset files. Data protection measures Access control Authentication Authorization Passwords The ten commandments of computer ethics were developed to guide the ethical of computers for everyone who uses computers. Computer ethics Refer to the moral values that guide individuals as they use computers. The ten commandments of computer ethics Thou shalt not use a computer to harm other people. Thou shalt not interfere with other peoples computer work Thou shalt not snoop around in other peoples files Thou not use a computer to steal Thou shalt not use a computer to bear false witness Thou shalt not use or copy software for which you have not paid. Thou shalt not appropriate other people intellectual output That shalt think about the social consequences of the program you write Thou shalt use a computer in ways that show consideration and respect Privacy Privacy refers to an aspect of IT that deals with the ability and power of an individual or organisation to deter what data in a computer system can be shared with a third party. The biggest problem caused by not protecting personal data identity theft. The biggest problem caused by not protecting personal data and proof read Pin (personal identification number) shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 30 Data integrity Refers to the accuracy, reliability and trustworthiness of data throughout its lifecycle To maintain integrity, data should not be altered by unauthorized people or programs, neither in transit nor when stored It may be compromised by Viruses, hacking and other computer threats Physical damage to st5orage devices Transfer errors, including unintended alterations or data, compromise during the transfer from one device to another Human error, either malicious or unintentional Data integrity best practices include: Validation of input data to avoid entering invalid Error checking (data verification) Security measures such as control, data encryption and prevention of data loss Data verification Data verification checks for accuracy and inconsistency when data is transferred from one source to another. Data validation methods a) Double entry entering data twice and compare two copies b) Proofreading categorising the data entered against the original document Data validation Validation refers to an automatic check that ensures that entered data is meaningful and sensible. In programming, it is crucial to validate input data. This serves to avoid abnormal or unexpected data from crashing Data validation also ensures that the data sent to connected applications is complete, accurate, secure and consistent. It ensures that data complies with the requirements and quality benchmarks. a) Data validation methods Techniques that makes sure data is accurate and clean. They include the following Range check Ensures data falls within a set of range between acceptable lower value and upper limit Is the scope of values that data can fall within E.g. maximum minimum range b) Type check Checks that data expected type entered is correct eg text or numbers E.g. date number email c) Check digit An extra number added to a digit which is calculated from other digits It ensures the rest of the number is correct d) Presence check Checks if the user entered something e) Length check Check the size of numbers or characters entered meet the expectations shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 31 System security Processes and techniques used to keep information confidential It entails the protection of information in transit or stored Network security measures They are put forward to fight against hackers, malware and potential threats such as Fire, theft, accidents, destruction of data, vandalism, hackers The measures include Fire wall A system that sit at some point of connectivity between the site it protects and the rest of the computer In most cases it is implemented as an appliance or part of the router A personal firewall may be implemented on an end user machine. All incoming and outgoing traffic must pass through it It controls the network E.g. a packet filtering router E.g. soft wares include pfsense, ipfire and smoothwall. It allows one to specify network traffic to block or filter from reaching your computer It allows one to let through only the traffic you want to reach. It accomplishes rules set by the user It does not protect one from malware A firewall router is an end point that connects several desktop computers, tablets, laptops and smartphones on the internet. A special category software that monitors activity across a network or a host computer Watches for suspicious activity and take automated action based on what it sees It works together with a firewall Intrusion detection system IDS Types Network IDS Host based IDS Signature based IDS Anomality based IDS Proxy is to act on behalf of something In computer networking, a proxy server is a server application that acts as an intermediary between a client requesting a resource and the server providing that resource.Instead of connecting directly to a server that can fulfill a request for a resource, such as a file or web page, the client directs the request to the proxy server, which evaluates the request and performs the required network transactions. This serves as a method to simplify or control the complexity of the request, or provide additional benefits such as load balancing, privacy, or security. Proxies were devised to add structure and encapsulation to distributed systems. A proxy server thus functions on behalf of the client when requesting service, potentially masking the true origin of the request to the resource server. It does not work when connected to virtual private network A way of scrambling data or changing data format so that it becomes meaningless to an unidentified person. The scrambled data is known as cipher text. Decryption a way of converting cipher text back to it's originally format plain text. Proxy server Encryption shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 32 Additional safeguards to computer network and data Implement a security plan eg burglar bars Make data and program backups Implement technical solutions eg firewalls Allow access to only authorized person's Change passwords frequently Use antivirus software Use biometrics for access Cyber crime Refers to offence or crime performed by or involving use of icts and the internet Common types of cybercrime Hacking, spam, cyberbullying and fraud, identity theft, phishing, spoofing and illegal or prohibited online content Effects of cybercrime Upsetting victims Loss of data Loss of customers Loss of revenue Examples of cyber crime Spoofing Deceiving people into believing an email or website originates from a source it does not Spoof, spoofs, spoofer, or spoofing may refer to: Spoofing (finance), a disruptive algorithmic-trading tactic designed to manipulate markets E-mail spoofing the creation of email messages with a forged sender address. Spoofing attack A situation in which a person or program successfully identifies as another by falsifying data... Sniffing Sniffing attack in context of network security corresponds to theft or interception of data by capturing the network traffic using a packet sniffer (an application aimed at capturing network packets). When data is transmitted across networks, if the data packets are not encrypted, the data within the network packet can be read using a sniffer. Using a sniffer application, an attacker can analyze the network and gain information to eventually cause the network to crash or to become corrupted, or read the communications happening across the network. Fraud Computer fraud is when a computer is used to gain an unfair advantage over another person. The crime of obtaining money or some other benefit by deliberate deception Common forms Identity theft, credit card fraud, scammers and con artist as well as financial swindles Hacking Illegally gaining access to computer systems Reasons for hacking Harass other individuals Show off shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 33 Gain access of computer services without paying Obtain information to sell Data backup Backup is an additional copy of data that can be used for restoring and recovering purposes. It is used when primary copy is lost or corrupted as a result of hardware failure, natural disasters and malicious damage. It is created by copying data to a separate storage device. Its purpose is to protect data from loss. It should be stored far enough from primary storage This is called of site backup Automate and streamline recovery process as much as you can. Automation lessens the risk of human error. Reasons for backup Disaster recovery Archival preserving for regulatory compliance. E.g. transaction records, emails, business work products Recovered in the event of a primary data failure. Primary data failures can be the result of hardware or software failure, data corruption, or a human-caused event, such as a malicious attack (virus or malware), or accidental deletion of data. Backup hardware Hardware that can be used to store backup copies Magnetic tape Most common type Cheap and affordable Reasonable performance and standardized formats Easy to use Challenges Sequential or linear access Cannot be accessed by multiple hosts simultaneously Short life span Extra care in handling Not easy to store Magnetic disc Ease of implementation Fast access More reliable Random access Multiple host access Types of backup Complete backup Involves everything the entire piece of work Useful on relatively small databases Faster restore time Slowest back up strategy shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 34 Partial backup Files changed since last backup Useful when it's important to have latest version of each file User defined backup Back up tools are most commonly found in operating systems. Cloud backup Online backup systems Drop box and Google drive Data loss prevention Avoid heat and vibration Defragmentate data Use of uninterrupted power supply Network security Physical security Strong passwords Virus � protection Create backup Maintain off-site copies of backup Use reliable backup media Data recovery Refers to recovery of lost data Process of salvaging data from damaged, failed, wrecked or inaccessible primary storage. Data loss can be caused by Natural disasters Computer virus Data corruption Computer crime human errors and bad use of information Data can be recovered from Deleted data Overwritten data Physical damage Data recovery tools Software used to recover data from damaged media E.g. recuva and Pandora Disaster recovery Catastrophic losses of entire systems can happen. Backup and recovery are essential they should not be considered as disaster prevention shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 35 They are critical components of disaster recovery plan Methods, processes and procedures needed to minimize the impact of a disaster upon information and data required for critical business process. The objective of a drop is to restore critical business process and it's focus is data recovery. Disaster recovery plan Factors to consider It should caver everything from usual reasons for data loss E.g. human failure, smoke, � fire and water damage to not so common incidents like data loss due to hackers and criminals. It should be adaptable to any possible hazard Stack holder should participate for them to be part of it and identify vulnerabilities and capacity. Conduct frequent updates in addition to hardware and software updates It should not be unnecessarily long. Creating a disaster recovery plan a) Guidelines b) Conduct a risk assessment c) Identify data recovery strategies Hot � site Mirrors that run concurrently with your main data center Fully equipped with hardware and software Cold � site Empty data center No server or workstation installed Provides power, cooling and office space which is ready in the event of a significant outage at the main data center Document the DRP It should be clear and precise The following should be included Steps for recovering from a disaster Contact information for software and hardware vendors Personnel familiar with the drop Location of backups Test the DRP See if it works Identify areas of improvement a shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 36 SYSTEMS ANALSIS AND DESIGN SYSTEM – A group of elements working together to achieve a common goal. SYSTEMS ANALYST -A person who identifies problems of the existing system and recommends the best solution to such a problem. DUTIES OFTHE SYSTEMS ANALYST Identifies the problem of the current system Liaises with the system users and determine their requirements. Find out facts important to the design of the new system. Determine the human and computer procedures that will make-up the system. Participate in the process of system implementation. By performing such duties the system analyst acts as: i. A consultant – can be called or hired to identify problems in a system. ii. A support expert- draws together professional expertise concerning computer hardware and software and their uses in business. iii. An agent of the change- bring new ideas into the organization QUALITIES OF A SYSTEM ANALYST Must have good written and oral communication skills for all managerial levels of an organization Must be able to work as a team Must be well educated with at least a degree Must be experienced in computers and at top managerial level Must have good management skills Must be a problem solver and see problems as challenges. Must be well disciplined Must be able to work under pressure and meet deadlines. Systems Development Life Cycle Systems development life cycle (SDLC) is a set of steps/ stages/phases which are necessary to go through in developing a new system to solve a problem. A conceptual model which includes policies and procedures for developing or altering systems throughout their life cycles The generic model The general or most common way of representing the cycle A model is a description either text or a diagram of how something is done. STAGES IN THE SYSTEMS DEVELOPMENT LIFE CYCLE Abbreviation: (P.F.A.D.I.C.M.) 1. 2. 3. 4. 5. 6. 7. Problem identification Planning Design Build Test deployment Maintenance shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 37 PROBLEM IDENTIFICATION/ RECOGNITION/DEFINITION and Problem Solving What is a problem? The difference between the actual and the desired situation This is where by the problems of the current system is stated. These might have been realized by system users or by managers (stakeholders). The system might be producing wrong results. We look for things which we do not want of the system These are referred to as problems of the current system The problem solving process The process of defining a problem determining the cause of the problem, identifying and prioritising and selecting alternatives for a solution Implementing the solution It has four problems 1. Define the problem Study current situation to find the problem Define the problem so it can be understood by others 2. Come up with an alternative solution Solving a problem is to think and come up with different ways of solving the problem They are known as alternative solutions since you can only choose one of the ways in solving the problem NB we don’t choose a solution because we want it. we should have good reasons for supporting it 3. Evaluate and select an alternative Consider an alternative in turn Consider issues like cost, feasibility, time to be taken and the organization’s expectations. at the end you select the alternative that you consider to be the best under the given circumstances 4. Implementing the solution After choosing a solution we now use it to solve the problem, then you can now start using the SDLC Data collection techniques Several techniques can be used but the most common are interview, questionnaire, observation and document analysis Document analysis in doing business it is advisable The process of finding information from the documents kept by the organization Questionnaires A document given to users and other stakeholders so that they give information needed. The person entering that does not include names so that they can say anything anonymously When the information is gathered together it is used to make decisions. Interviews Interview is way of collecting important information from people. They is a interview or and interviewee Interviews are done face to face which means the interviewee will be talking to the interviewer directly. Its main advantage I I something is not clear, further questions will be asked to make the point more understandable some people may be afraid to say out what they think because of fear. shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 38 Observation It involves the one looking for information and the one doing the work. The one looking for data will go and watch thing happening. When you are watching, you write down notes The methods is good because it makes one to easily understand this because you can get information direct from where it is unlike when sending someone else describes it for you. FEASIBILITY STUDY It involves an evaluation of proposal to determine if it is possible to construct a new system or just modification of the existing one. It provides directions and reasons for continuing with the development. Importance of feasibility study The information obtained from the feasibility study is used to: Identify things needed to make the business work Point out any business related problems and their solutions It provides a strong foundation for developing your business or system. It determines early that an idea will not work It prevents disappointments, saves time and money After completing a feasibility study, you produce a feasibility report Types of feasibility TECHNICAL FEASIBILITY- Determines if the organization can obtain software, equipment and personal to develop, install and operate the system and even to maintain it. Questions that need answering during technical feasibility are Do we have the necessary technology? Do we have the necessary expertise in form of the people who will develop and use it? Does the company have the technological resources to undertake the project? Are the processes and procedures conducive to project success? Do the hardware and software available have the ability to support the new system? ECONOMIC FEASIBILITY Determining whether the benefits of the new system will outweigh the estimated cost involved in developing, purchasing, assembling requirements, installing and maintenance of the new system. The main task of this type of feasibility is to identify and quantify all the benefits that will be derived from the project and all the expenses in obtaining the system. Compare the total benefits and total expenses. That is total benefits minus total expenses. OPERATIONAL FEASIBILITY Determines whether the current work practices and procedures are adequate to support the system e.g. effects on social lives of these affected by the system, can it work well with existing hardware etc. SOCIAL FEASIBILITY A measure of the system acceptance by the public if it will meet the norms and values of the society. ANALYSIS STAGE -The major function is to determine the requirement of the proposed or new system. It consists of studying the current system followed by defining the new system. Work out a new system requires, decide what the new system has to do. 4. shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 39 SYSTEM ANALYSIS System analysis is when the developers of the system develop and documents the properties of a system. The problems and its solution structure are put in a simpler way to alternatives and are examined and the most suitable one selected for implementation. After thee analysis phase follows a design phase in which several types of documents are drawn. The documents are mostly diagrams, for example, flow charts, decision tables and psuedocodes. Systems analysis is the process of planning a new system to replace or complement the existing one. Analyses specifies what the system should do and design states how to achieve that. The examination should be carried should always be initiated by the people involved in the situation (or who will be involved in a new situation. The system analysts suggest solutions and do not make business decisions. Alternative solutions A solution is an answer to a given problem or a procedure that draws benefits from a business opportunity. There are many different ways of solving one or the same problem. These possible ways are known as alternatives. During system analyses , the systems analysts, the system developers need to explore seversl alternatives and eventually choose and justify one of them. The chosen one should be the best under given conditions. Common system alternatives are simply buying a a completely new system to re[place an old one, modifying the old one in accordance with the new requirements and developing a completely new system from scratch the old one Evaluation of alternatives An evaluation of Alternatives would be by examining the benefits and drawbacks of each. During the evaluation of alternatives, careful consideration is given to social, economic and ecological factors that influence the predicted outcome. It is, advised to use discussion and visual aids to help explain alternatives There is need of an evaluation criterion Evaluation is a systematic determination of a subject’s merit, worth and significance, using criteria governed by a set of standards. An evaluation is a well thought factors that are used to judge the worthiness of an alternative. Factors to be included in evaluation are effectiveness of the alternative solution, cost of the resources needed, the expertise needed and the time required. Data Flow Diagrams (DFDs) Data flow diagrams (DFDS) models a perspective of the system mostly readily understood by users They show a flow of information through the system and the activities that process this information. They provide graphical presentations of the system to the users both specialist and no specialist. It enables stakeholders to work together during the analyses and specification of requirements They provide simple and easy sets of constructs to follow. They show a clear path information should flow through a process or system It includes Data inputs Outputs Data stores Sub processes They are build using standardized symbols and notations to describe various entries and their relationships. shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 40 Physical and logical data flow diagrams Logical data flow diagrams Focus on what happens in a particular information flow What information is being transmitted, what entities are receiving that information and what general processes occur. Processes described are business activities. It does not go into technical aspects of a process or system Physical data flow diagrams Focus on how things happen in information flow They specify the software, hardware, files and people involved in information flow. A detailed physical data flow diagram can facilitate the development of the code (program instructions) needed to implement a data system Dfd symbols They are four basic symbols External entry Process Data store Data flow Processes are the activities carried out by the system that use and transform information. They are as rectangles such as order supplies and make payments The rules for processes Process names should be an imperative verb specific to the activity in question, followed by a meaningful description of the object of the activity for example Create Contract or Schedule Jobs, as opposed to using very general or non-specific verbs, such as Update Customer Details or Process Customer Call. Processes cannot act as data sources or sinks. Data flowing in a process should have corresponding output., which is directly linked to it. Rules for drawing data flows - Information always flows to or from a process An exceptional occasion to this rule is a data flow between two external entities - Data stores may not be directly linked by data flows. A process needs to take place for data to move from a data store - Information may not flow directly from a data source to an external entity. - The sources and sinks of data flows are always represent by external entities - When something important happens to a data flow, as a result of a process acting on it, the label of the resulting data-flow should reflect its transformed status External entities: These are sources from which information, flows into the system and the recipients of the information leaving the system External entities are noted as rectangles, such as “Supplier” or “Customer”. In other words, external entities are referred to as sources and sinks Data stores: This is where information is stored within the system. They are noted as rectangles with two parts, such as “Supplier Details” and “orders”. A data store is represented in the data flow diagram by a long rectangle, containing two locations. D1 Supplier file The left hand box is the identifier, which is representing a numerical reference prefixed by a letter. The right hand rectangle is labelled with name of the data store shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 41 Rules for data stores - One conversion that could be used is to determine the letter identifying a data store by the stores nature “M” is used where a manual data store is being depicted. “D” is used where it is a computer based data store “T” is used where a temporary data sore is being represented. Data stores may not act as data stores or sinks. Drawing data flow diagrams - Each process should have at least one input and output. Each data store should have at least one data flow in and one data flow out. Data stored in a system must go through a process All process in a DFD goes to another process or a data store. The benefits of data flow diagrams - They provide system scope and boundaries since they are indicated in the diagrams They provide an overall vie of the complete system, as well as a more detailed breakdown and description of individual activities Activity diagrams These consist of activities, states and transitions between activities and states. Benefits of activity diagrams - Demonstrate the logic of a computer program Describe the steps to follow in doing a project Illustrate a user training programme Describe how to perform an experiment in science Basic components of an activity diagram Action Decision node Control flows Start node End node shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 42 SYSTEMS DESIGN The function is to design a new system that fulfills the requirement of users and of management. Tasks performed by the analyst in this phase include designing the program structure of the new system in cooperating measures to guard against any computer crime e.g. password, encryption of sensitive data. - Consider possible solutions which fit the analysis. -Consider whether new hardware is required. -Consider whether new software is required INPUT/OUTPUT DESIGN Input is normally the raw data processed to produce output During this stage, developers must consider input devices The quality of the input determines the quality of the output The following properties are expected - it should save a specific purpose effectively such as storing, recording and retrieving information - it ensures proper completion with accuracy. - It should be easy and straight forward to use - It should focus on the users consistency, attention and simplicity Objectives for input design - Design data entry and input procedures - Reduce input volume - Design input data records, data entry screens and user interface screens - Use validation checks and develop effective input controls Input methods It is important to design appropriate data input methods to prevent errors while entering data. A system should prevent the user from making mistakes by - Clear form design by leaving enough space for writing legibly - Clear form design - Reducing key strokes - Immediate error feedback Some of the popular data input methods - Batch input method - Online data input method - Computer readable forms - Interactive data input. Output design This is the most important task of any system Types of outputs needed identified in this stage and consider the necessary outputs and prototype report layouts Objectives of output design - Should serve the intended purpose and eliminates the production of unwanted outputs - They should meet end users requirements - Deliver the appropriate quantity of output - Form output in an appropriate format and direct it to the right person - Make output available on time for making decisions Types of outputs - Internal outputs stay inside the system to support the system’s users and managers - External outputs leave the system to trigger actions on the part of their recipients or confirm actions to their recipients shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 43 Output formats - Tabular output - Graphic output - Narrative output User interface design User interface refers to a way in which a computer system presents itself to the user and the way the user interacts with the computer General considerations before engaging on designing a use interface - The problems to be solved – does it include inputting, processing, outputting or storage - If it accepts input, how are you going to input? - How are you going to process? - How are you going to output? Form design Important factors - Who will use them - Where would they be delivered - The purpose of the form or report Objectives of good form design - To keep the screen simple by giving proper sequence, information and clear captions To meet the intended purpose by using appropriate forms To ensure the completion of the form with accuracy To keep the forms attractive by using icons, inverse video or blinking cursors To facilitate navigation Database or file design The organization of data according to a database model Database design involves classifying data and identifying interrelationships. Involves designing tables/files and validation rules. Data modeling The first process of database design Also referred to as conceptual design It describes the data contained in a database, the relationships between data items, the constrains on data The second step is the expression of data items, the relationships and constrains using the concepts provided by the high-level data model. The third step is the database design. They two sub steps - Database logical design (defines a database in a data model of a specific DBMS) - Database physical design (defines the internal database storage structure, file organistion or indexing techniques). Data is represented using a certain data model. The data model is a collection of concepts or notations for describing data, data relationships and data semantics and data constrains shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 44 A relational database organizes data in tables (or relations). A table is made up of rows and columns. A row is also called a record (or tuple). A column is also called a field (or attribute) System flow charts What is a flowchart? A diagram that shows step by step progression through a procedure or system especially using connecting lines and a set of conventional symbols. Basic flow chart symbols Symbol Name Function START/END AN OVAL REPRESENTS a start or end point Aroow An arrow is a connector that shows relationships between the representative shapes Input/output A parallelogram represents input or output Processs A rectangle represents a process Decision A diamond indicates a decision To create a good flowchart you must first familiarise yourself with the most commonly used flow chart symbols What is input and output in a flowchart? These are fundamental blocks of a process used to describe a computer program. The input is provided by a user. The program will have a code to interprate the input and generate an output. Algorith design A procedure is a finite procedure of well defined instructions. They can be mechanically carried out in a in a specific amount of time. A procedure must break up the problem solution into parts that the recipient party can understand and execute with minimum effort.the procedure must consists of smaller steps which the computer can understand. A solution is a procedure , or method , for transforming the current situation to the desired one . Points to consider when developing an algorithm − − − − Use suitable identifier names Are expressed using constraints such as assignment and sequence Simple algorithms consist of input, process and output In writing algorithms and their coreesponding programs we use control structures to direct the course of program execution DEVELOPMENT AND TESTING Coding Coding simply refers to programming This is the actual development of the system (software) whereby you use a programming language platform to write computer program.design documents from the previous stages are used shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 45 Testing A way of finding out and correcting errors For it to be effective it needs to be planned A test plan document is prepared The test plan is a dynamic document A test plan document that is current at all times determines the success of testing a program The test plan document i. A document that we share with business analysts, project managers, development teams and the other teams. It helps in improving the level of transparency of the quality assurance team. ii. It is documented by the quality assurance manager based on the inputs from the quality assurance team members iii. It is typically allocated with 1/3 of the time taken for the entire quality assurance engagement. The other 1/3 is for test designing and the rest for test execution iv. This plan is not static and is updated on an on-demand basis. The more detailed and comprehensive the plan is. The more successful will be the testing activity CONSTRUCTION STAGE The new system has to be created and tested according to the specification set out in the design. A new system has to be written. -System testing programs and methods ought to be tested and debugged. Tests are carried out. DOCUMENTATION Improvements suggest that we develop the system form one level to another level which is usually better There is need to document the details of the improvement The details include the the shortfalls of the original system. How the new system will address those shortfalls, the methods/techniques used to develop the system. Reasons for documentation Visibility. This refers to the ability of the developers to see the activities what took place at different stages User support. Documentation is used to support users of the system during use. When the user is not sure about carrying out a certain task, he /she will consult the available documentation. In most cases it is in the form of a user manual. Team communication. Normally computer systems are developed by a team. The team includes programmers, system analysts, software engineers, software project managers and so on. Documentation acts as a means of communication for the team. Maintenance and evolution. Those who maintain the system are usually different from those who develop it. The developers should document the process for the maintenance people to have a reference. Requirements document Its is an official statement of what is required of the system developers and what the system should do and not how it should do it. It acts as a contract between between the developer the customer and the user. Structure of the document Introduction it gives the purpose of the system Current software architecture describes the current state of affairs of the system Proposed architecture it describes the high level architecture of the systems under development. It consists of the following shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 46 Overview of the system. A brief description of the system, what it does, why it was developed and development constraints Subsystem decomposition. Gives names of subsystems and their associated responsibilities. The subsystem must interact with the whole system to provide expected services Hardware and software assign hardware and software to the identified system Data mangement specify the data stored/used by the system Access control and security describes the access levels and the methods to be used to authenticate users in the system. Data directory gives the definition of terms used to describe data that is used in the system Types of documents Project plan document An overall plan of developing the software. It gives direction to the development process Structure of the document Introduction it includes the purpose and objectives of the system Project organisation describes the different phases of the project from the problem of the statement to the delivery of the system. It includes time frames and resources to be used Risk analysis it identifies the possible risks of developing the system and mitigation measures Hardware and software requirements lists all the hardware and software required in developing the system. It also lists that are already available Work breakdown structure. It is the breakdown of the entire project work into smaller manageable tasks. Project schedule. It specifies the duration start times and completion times of each task identified in the work breakdown structure Monitoring and reporting mechanism. It promotes effective communication by letting every team member to know the communication channels User training. Users are the ones who use the system in most cases they don’t have the experience as the developers. Users should be trained on how to use the system before and during system use. During training they should know their roles in detail.the following is under user training. User training guidelines Identify appropriate trainees and trainers Establish measurable objectives Use appropriate training methods Select suitable training site Use understandable training materials Training topics Use of the system Related computer concepts Information system concepts Organisational bussines strategies System mangement System installation How to use the system SYSTEM IMPLEMENTATION shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ 47 -User documentation is prepared. -Users are trained to use the new system. 4 -Technical documentation is prepared so that the new system can be maintained. CONVERSION/CHANGE OVER -This involves putting the new computer system into operation that is changing from the old system to the new one. -It involves file conversion which is the changing of the old data files into the current format. -Different changeover methods can be used and these include: PARALLEL RUN This includes or involves both the old and the new system concurrently until the new system proves to be efficient. It involves operating the new and old system simultaneously until management is confident that the new system will perform satisfactory. ADVANTAGES OF PARALLEL RUN -Results for both systems are compared for accuracy and consistency. -If the new system develop problems, it will be eas shewag.tm@gmail.com 0779814951 © Tinashe Wagner Makoni Simplified approach to computer science Sir Wagner ™ shewag.tm@gmail.com 0779814951 48 © Tinashe Wagner Makoni
