Fundaments of Hardware &
Software
Section 1
Name: _____________________________
Lecturer: Ms. Y. Stewart
2009-2010
Section 1: Fundaments of Hardware & Software
INTRODUCTION
COMPUTER: A computer is a device that accepts information ( input in the form of digitalized data) and
manipulates it for some result based on a program or sequence of instructions on how the data is to be
processed. This information can then be displayed or stored for future use.
Data: This collection of raw unprocessed facts, figures and symbols. Computer processes data to create
Information hence Information is data that is organized, meaningful and useful.
Hardware: this is the physical components contained in a computer system. For example; printers, monitor and
speaker.
Peripheral Device: any hardware device connected to and controlled by the central processing unit. Examples
of peripherals are modems, disk drives, printers, scanners and keyboard.
Software: also called a program is a series of instructions that tells the hardware how to perform tasks. Without
software most hardware are useless.
Backing Store: Storage external to the computer used for large quantities of data or large programs. Backing
store is also known as secondary store, auxiliary store or external store.
User: a user is someone who communicates with the computer or uses information it generates.
INFORMATION PROCESSING CYCLE
Input is any data or instructions you can enter into a computer. Output is data that has been processed into
information and displayed to the user. Computer processes input (DATA) into output (INFORMATION). Storage
is an area in a computer that can hold data and information for future use. The series of input, process, output
and storage activities is called Information Processing Cycle.
Created by: Ms. Yanecia Stewart (2009)
ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
MAJOR HARDWARE COMPONENTS OF A COMPUTER SYSTEM
A Computer contains many electric, electronic and mechanical components known as hardware. These
components include input devices, output devices, a system unit, storage devices and communication device.
The main components of a computer system will be further discussed in this Section. These include:
Input Devices
Output Devices
Secondary Storage Media
Central Processing Unit (Processor)
Memory
INPUT DEVICES AND MEDIA
An input device is any hardware components that allow a user to enter data and instructions into a computer.
Most commonly used input devices and media are discussed below:
Input device/media Description
Keyboard: Contains key that allows you to type letters of that alphabet,
numbers, spaces, punctuation marks and other symbols. A computer
keyboard also contains other keys that allow you to enter data and
instructions into a computer. Braille keyboards are also available which
contains Braille symbols on each keyboard keys.
Mouse: Is a small handheld pointing device that contains at least one
button. The mouse controls that movement of a symbol on the screen
called a pointer. E.g. as you move the mouse on a flat surface, the
pointer on the screen also moves. With the mouse you can make
choices, start a process and selects objects.
Light Pen: A light pen is a handheld pointing input device that can detect
the presence of light. To select objects on the screen, a user presses the
light pen against the surface of the screen or points the light pen at the
screen and then presses a button on the pen.
Digital Camera: Allows you to take digital pictures. Images viewable
immediately on camera and can be Downloaded to the computer or
posted pictures to Web
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ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
Joystick: Users running game software or flight and driving stimulation
software often use a joystick as a pointing device. A joystick is a vertical
lever mounted on a base. You move the lever in different directions to
control the actions of the simulated vehicle or player. The lever usually
includes buttons called triggers you press to activate certain events.
Touch Screen /Touch terminal: Allows users to enter limited amounts of
data by touching the surface of a sensitized video display monitor with a
finger or a pointer. Because they require a lot of arm movements, you
do not enter large amounts of data into touch screens. Instead, you
touch words, pictures, numbers, or locations identified on the screen.
Touch screens are often found in retail stores, restaurants, and shopping
malls.
Scanner: Reads printed text and pictures and then translate the results in
a digital form the computer can use.
Magnetic Ink Character (MICR): Used primarily in cheque processing for
the banking industry. Characters on the bottom of a check identify the
bank, checking account, and check number and are preprinted using
special magnetic ink. A MICR reader translates these characters into
digital form for the computer.
Microphone: Voice input device that captures sound and into digital
form for processing by the computer. Microphones can serve as input
devices for music, spoken words and other sounds.
Graphic Tablet (or digitizing tablet, graphics pad, drawing table): is a
computer input device that allows one to hand-draw images and
graphics, similar to the way one draws images with a pencil and paper.
These tablets may also be used to capture data or handwritten
signatures. A graphics tablet consists of a flat surface upon which the
user may "draw" an image using an attached stylus, a pen-like drawing
apparatus. The image generally does not appear on the tablet itself but,
rather, is displayed on the computer monitor
Webcam :Web cam is used to capture video and still images, send e-mail
messages with video attachments, add live images to instant messages,
broadcast live images over the Internet, and to make video telephone
calls on Internet
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ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
Biometrics Systems: Biometrics refers to methods used to authenticate
person’s identity by verifying unique personal characteristic based upon
one or more physical or behavioral traits. Examples are
 Fingerprint reader which captures curves and indentations of
fingerprint
 Hand geometry system measures shape and size of person’s hand
 Voice verification system compares live speech with stored voice
pattern
 Signature verification system recognizes
shape of signature
 Iris recognition system reads patterns in blood vessels in back of
retina
Sensors: This is a device that collects data directly from the environment
for input into the computer. There are many types of sensors that are
used to measure things like heat, or wind speed. Sensors could be used
to monitor the temperature in a furnace.
Voice Response Unit: A voice response unit responds to voice
commands, rather than input from a keystroke or a mouse. This device
enables output from a computer system in the form of user recorded
words/phrases, music, alarms or anything that can be recorded as
sounds.
Remote Control: is an electronic device used for the remote operation of
a machine e.g. a multimedia projector remote control.
OPTICAL READERS
An Optical Reader is a device that uses a light source to read characters, marks and codes, and then
converts them into digital data that a computer can process. Two technologies used by optical
readers are optical characters recognition and optical mark recognition.
Optical Mark Reader (OMR): This is a technology that reads hand drawn
marks such as small circles or rectangles. A person places these marks
on a form, such as test, survey, or questionnaire answer sheet. With a
test, the OMR device first scans the answer key sheet to record correct
answers based on the pattern of the light. The OMR device then scans
the remaining documents and matches their patterns of light against the
answer key sheet.
Optical character recognition (OCR): Is a technology that involves
reading typewritten, computer-printed, or hand-printed characters from
ordinary documents and translating the images in a form that the
computer can process. Most OCR devices include a small optical scanner
for reading characters and sophisticated software to analyze what is
read.
Created by: Ms. Yanecia Stewart (2009)
ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
Bar Code reader: A bar code scanner is an optical reader that uses laser
beams to read bar codes. A bar code is an identification code that
consists of a set of vertical lines and spaces of different widths. The bar
code identifies the manufacturer and the item.
Point-of-Sale Terminals: The location in a retail or grocery store where a consumer pays for goods or services is
the Point of sale (POS). A POS terminal is a device that reads data at the source of a transaction and stores it for
transmission directly to the computer system for processing. Most retail stores use a POS terminal to record
purchases, process credit or debit cards, and update inventory. The POS terminal is a combination of an
electronic cash register, bar code reader and printer. When the cashier scans the bar code on the item, the
computer uses the manufacturer and item numbers to look up the price of the item and the complete product
name in a database. Then the price of the item in the database shows on the display device, the name of the
item and its price prints on the receipt, and the item being sold is recorded so the inventory can be updates.
OUTPUT DEVICES
An output device is any hardware component that can convey information to a user. Three commonly used are:
AUDIO OUTPUT
Speaker: speakers allow you to hear music, voice and other sounds generated by the
computer.
Head-phones: A pair of listening devices joined by a band across the top of the head and
worn in or over the ears
Earphones: allow you to hear music, voice and other sounds by placing the ends of the
earphones directly into the ear.
Created by: Ms. Yanecia Stewart (2009)
ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
VISUAL DISPLAY UNIT
The computer monitors, like television, display computer output for the user to view. The monitor has various
names; screen or Video Display Unit (VDU). When purchasing a computer
monitor, the following features are important.
Color : monochrome, gray scale or colored
Size: Monitors come in various sizes; 14 inch, 15 inch, 17 inch, 20
inch and even larger monitors can be bought at higher prices. A 15
inch can display 800 pixel horizontally and 600 pixel vertically. A 20inch monitor can display 1280 by 1020 pixels.
Resolution: Pictures on a screen are made up of tiny dots called
pixel, short for picture element. Resolution is the number of
horizontal and vertical pixels in a display device. The more pixels per
inch, the better the quality of the picture
Technology: cathode ray Tube (CRT )or Liquid crystal Display (LCD)
The on-screen display enables you to see how the applications are processing your data, but it important to
remember that the screen display is not a permanent record but rather called a SOFTCOPY as opposed to the
printed output called a Hardcopy.
PRINTERS
Another popular output device is the printer. A printer is a device used to output text and images from the
computer onto a paper. Therefore unlike monitors, printers produce hardcopy. Printers can be placed in two
categories: Impact and Non-impact printers.
IMPACT PRINTERS
Impact printers are printers that transfer data onto paper by hitting the paper
using a hammer in a similar way to a type writer. As you can expect, impact
printers tend to be very noisy. The characters to be printed are pressed
against an inked ribbon onto the paper. After a while the ribbon becomes
worn and faded and must be changed. Multiple copies of documents can be
printed using carbon paper.
There are two types of impact printers: Line printers and Character printers.
Line Printers: Line printers are printers that can use multiple print hammers to print an entire line of text at one
time. Although a line printer can print test at a very fast rate, it has some disadvantages. First of all, it cannot
print graphics and secondly the text that it prints isn’t of very high quality.
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ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
Character Printers: Character printers print a character at a time. It is no surprise, therefore that these are
slower than a line printer. The two main types of character printers are:
1.
Daisy Wheel Printers: These printers use a wheel containing characters that rotates until the right
character is facing the paper. A hammer is then used to force the character into the ink ribbon onto the
paper. Daisy wheel cannot print graphics nor can it print different fonts in a single document.
2. Dot Matrix Printers: these have a print head capable of firing tiny pins arranged in a matrix. As the
print head moves back and forth, these pins strike the ribbon causing dots to be arranged to form
characters. It can be used to print very simple graphics and some dot matrix printers can print in color.
Although impact printers are not common these days, they are normally used to print bills or forms that require
carbon copies and special reports that require large continuous sheets (some payroll and accounting reports).
NON-IMPACT PRINTERS
Non-impact printers are printers that print using methods that do not involve striking the paper using an inked
ribbon. They are generally faster than most impact printers and a lot quieter. Non-Impact printers can also
provide various fonts styles and excellent graphics. Non-impact printers cannot print carbon copies and some
types are also much more expensive.
1. Inkjet Printers: these are printers that squirt very small drops of inks on the paper in order to produce
text and images. This is the most popular types of printers (especially in the home) since, although it
produces high-quality output, at a relatively high speed, it is still fairly cheap.
2. Laser Printers: uses laser light to make patterns of ink on a drum, this drum then transfer the ink to the
paper, and finally a heating process fuses the ink to the paper. Laser printer gives excellent print quality
and prints very quickly.
PLOTTERS
Plotters are sophisticated printers used to produce high quality
drawings such as blueprints, maps and circuit diagrams. These printers
are used in specialized fields such as engineering and drafting and are
usually costly. Plotter uses the same technology as inkjet printers but
on a much larger scale.
TERMINOLOGIES
Microfilm: A continuous roll of photographic film, used for storage of miniaturized text, which can be read only
with magnification by a reader/printer machine. Applications of microfilm are widespread. In some libraries,
archived files are routinely converted to microfilm to save space. Reader/printer machines are usually available
in libraries with microfilm holdings for viewing and making copies. Large organizations use microfilm to archive
inactive files. Banks use them to store transactions and cancelled checks. The use of microfilm provides a
Created by: Ms. Yanecia Stewart (2009)
ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
number or advantages. They greatly reduce the amount of space; they are inexpensive and have the longest life
than any other storage media.
Machine Readable: The term machine-readable or computer-readable refers to information encoded in a form
which can be read or understood by a machine / computer and interpreted by hardware and / or software.
Machine-readable data includes files stored on disk or tape, or data that comes from a device connected to a
computer.
Human Readable: Characters that can be read by persons, such as letters and numbers, as opposed to bar
codes.
Hardcopy: Output that is tangible i.e. can be touched, for example printed paper.
Softcopy: Output that is intangible i.e. can be seen but cannot touch, for example, monitor output.
Character: one of the sets of symbols that may be represented in a computer. Character may be letters, digits,
symbols, etc.
Print Quality: The clarity of printer output, often determined by resolution. Print Quality is measured in dots per
inch (dpi), this determines how smooth a diagonal line the printer will produce.
Printer Speed: The speed of a printer is measured in Character Per Second (CPS), Lines Per Minute (LPM) and
Pages Per Minutes (PPM) . The faster the printer, the more expensive it is.
SYSTEM UNIT
The System Unit is the main part of a personal computer. The system unit includes the chassis, processor, main
memory, bus, and ports, but does not include the keyboard or monitor, or any peripheral devices.. The two
main components of the System unit are the Central Processing Unit (CPU) and the MEMORY.
CENTRAL PROCESSING UNIT (CPU)
The central processing unit (CPU), commonly referred to as the processor or central processor, is the part of the
computer system where the manipulation of symbols, numbers, and letters occurs. It is primarily responsible
for performing the arithmetic calculations within the computer system and to direct all input/output activities.
The CPU has two fundamental sections.
Control unit: the command centre of the processor that interprets program instructions directs internal
operations and directs the flow of input/output to or from RAM. (Random Access Memory)
Arithmetic and Logic Unit (ALU): The arithmetic-logic unit (ALU) performs the computer's principal logical and
arithmetic operations. It adds, subtracts, multiplies, and divides, determining whether a number is positive,
negative, or zero. In addition to performing arithmetic functions, an ALU must be able to determine when one
Created by: Ms. Yanecia Stewart (2009)
ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
quantity is greater than or less than another and when two quantities are equal. The ALU can perform logic
operations on letters as well as numbers.
MEMORY
Memory consists of electronic components that stores instructions waiting to be executed by the processor,
instructions on how to carry out specific tasks, and the results of processed data (information). Memory,
sometimes referred to as immediate access storage is the temporary holding space for data and instructions.
There are two types of memory:
Random Access Memory: The memory area in which all programs and data must reside before programs can be
executed or data manipulated. Users can modify programs in RAM. RAM can be written from and is volatile,
that is, information is lost when the power is switched off. RAM stores programs and data that are currently
being used by the CPU. RAM is sometimes referred to as primary storage.
Read Only Memory: this is the area of memory where the user cannot modify information. ROM can be read
but not written to and is non-volatile, that is, the program and data is stored permanently. ROM contains
startup information for your computer system. The information in ROM is burned in by the manufactures.
THERE ARE DIFFERENT TYPES OF ROM:
Programmable Read only Memory (PROM): is a blank ROM chip onto which a programmer can write
permanently. Once a programmer writes the microcode onto the chip, it functions like a regular ROM chip and
cannot be erased or changed.
Erasable Programmable Read Only Memory: erasable programmable read-only memory. A type of memory
chip that can be erased by removing it from the circuit and exposing it to ultraviolet light. The chip can then be
reprogrammed.
TERMINOLOGIES
An expansion slot is a socket on the motherboard that can hold an adapter card
An adapter card enhances functions of a component of the system unit and/or provides connections to
peripherals e.g. Sound card and video card
A port is the point at which a peripheral attaches to or communicates with a system unit e.g. usb and VGA
ports (see examples of ports in class)
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ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
SECONDARY STORAGE DEVICES
Secondary storage (often referred to as backing store or disk storage), hold data, instructions and information
for future use. Storage differs from memory, in that it can hold these items permanently. Memory by contrast
holds items only temporarily while the processor interprets and executes instructions. A storage medium is the
physical material on which a computer keeps data instructions and information. A storage device records and
retrieves items to and from a storage medium. Storage devices often function as a source of input because they
transfer items from storage into memory. Examples of storage media are floppy disk, hard disk , optical disk and
magnetic tapes.
MAGNETIC TAPE
Data is read and written on the surface of a tape the same way as an audiocassette. Difference is that a
computer tape drive writes digital
data. Tape drive usually store data
that is not been used very often,
such as backup copies of our hard
disk. Because a tape is a long strip
of magnetic material, a tape drive
has to write data 1 byte after
another . A tape drive uses
sequential access (sometimes called serial access). This is slower than the direct access provided by media such
as hard disks and floppy diskettes. When you want to access specific data on the tape the drive has to scan
through all the data that you don’t need, to get to the data you want thus resulting in slow access time.
The access time varies depending on the:
Speed of the drive
Length of the tape
Position on the tape to which the head wrote the data in the first place.
FLOPPY DISK DISKETTE
A floppy is a portable (can remove the floppy from one computer and insert it in
another), inexpensive storage medium that consists of a thin, circular, flexible
plastic disk with a magnetic coating enclosed in a rigid plastic casting which
automatically closes when the disk is removed from the disk drive. Today the
most widely used floppy disk is 3.5 inches wide called micro –floppy disk and
typically can store up to 1.44 megabytes (MB) of data.
When the computer needs s to read data from the disk, the head actuator moves
the read/write head over the surface of the disk. The head actuator is a
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ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
mechanism that moves the read/write head to the area that contains the desired data. When the read/write
head is in the correct position, it begins reading the data into the computer memory.
How data is stored on the floppy
A track is a narrow recording band that forms a full circle on the surface of the disk.
The disk’s storage locations then are divided into pie-shaped sections, which break
the tracks into small arcs called sectors. A sector is capable of holding 512 bytes of
data. A cluster is 2 or more sectors combined. The read-write head of the diskette
drive can quickly get into position to read data from or write data to the disk
surface. So a diskette provides Direct Access storage.
HARD DISK
The hard disk is the main storage device in your computer. It is a bit like a filing
cabinet: all of your data files and applications software are stored on it. The hard disk
contains a number of metal platters which have been coated with a special magnetic
material. The data is stored in this magnetic material. Thus, the hard disk is known as
a magnetic storage device.
In order to access the data, the platters spin many thousands of times a second and a
magnetic read and write head floats just above the surface of the platter.
To protect the platter’s surface hard disk are enclosed in a sealed container. If the read/write head were to
encounter an obstacle such as dust, hair and smoke the head would bounce on the disk surface causing serious
damage (head crash- in which the head touches the disk, this can destroy data stored in the particular area of
the crash). When you hear the term 'hard disk crash', this refers to the read/write head crashing down onto the
surface of the hard disk. There is a risk every time this happens that the data stored in the section just where the
head crashes might be damaged. That is why it is a bad idea just to switch the computer off at the wall without
shutting it down properly.
Hard disks are measured in Gigabytes. A typical hard disk size will be around 120 GB - 1 Terabyte.
It is possible to also have an external hard disk which can be plugged into the computer and used to back up
your data and then stored in a different place to keep it safe.
Like Floppy the hard disk must be formatted before use. The
formatting process creates tracks and sectors like those of a
floppy disk. A cylinder is a location made up of same track
location on all platters. Cylinder 0 refers to the outmost track on
all platters.
Advantages
large storage capacity
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ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
stores and retrieves data much faster than a floppy disk or CD/DVD
Stored items are not lost when you switch off the computer
Cheap on a cost per megabyte compared to other storage devices
Disadvantages
Far slower to access data than ROM or RAM chips
Hard disks can crash which stop the computer from working
Regular crashes can damage the surface of the disk, leading to loss of data in that sector
The disk is fixed inside the computer and cannot easily be transferred to another computer.
TERMINOLOGIES
Fixed Head: one read write head per track with heads mounted on a fixed arm.
Movable head: one read write head per side with head mounted on movable arm
Exchangeable: these are detached external hard drive, which have their own power supply and are not built
into the system cabinet, can store gigabytes of data.
OPTICAL DISCS
An Optical disc is a type of storage media that consist of flat, round, portable disc made up
of metal and plastic that is written and read by laser. Optical disc primarily stores
software, data, digital photographs, movies and music. Some optical disc are read only,
meaning users cannot write (save) on the media. Others are read/write, which allows
users to save on the disc.
An optical disk uses a different method to record data from the magnetic disk. To record data on an optical disc,
a high powered laser light creates lands and pits in a plastic layer on a circular disk. A laser that reads the optical
disk, these lands and pits are read as 1,s and 0’s by shining another laser on the disk.
There are two forms of optical disks, namely
Compact Disc (CD)
Digital Versatile Disk (DVD)
COMPACT DISK (CD)
A standard medium for storage of digital data in machine-readable form, accessible with a laser-based reader.
CDs are 4-3/4'' in diameter. CDs are faster and more accurate than magnetic tape for data storage. Faster,
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ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
because even though data is generally written on a CD contiguously within each track, the tracks themselves are
directly accessible. This means the tracks can be accessed and played back in any order. The typical storage
capacity of a CD is 700MB
Some variations to CD are:
CD- ROM – A digital disk that users can read but not write or erase- hence the name read-only-memory.
Manufactures write the contents of standard CD-ROMs
CD-R – Multisession optical disc on which users can write, but nor erase, their own items such as text, graphics
and audio.
CD-RW – This is a multisession optical disc that can be erased and written on repeatedly. These use a different
material for the laser to work and can be softened and lasered again. It functions like a magnetic disk but has a
greater capacity for data storage. The average CD-RW disk can be erased and rewritten over 1000 times.
Advantages
Small and portable
Very cheap to produce
Most computers can read CDs. If there is no CD drive, a DVD drive can usually read them
Fairly fast to access the data - quicker than a floppy disk or magnetic tape
Disadvantages
Fairly fragile, easy to snap or scratch
Smaller storage capacity than a hard drive or DVD
Slower to access than the hard disk.
DIGITAL VERSATILE DISK (DVD)
DVD optical disk has the same physical size as a compact disc, but with the ability to store seven (7) times as
much data. A DVD optical disk can gave 17GB of storage space. This increase in storage capacity is partly
achieved by:
Placing the tracks on the disk closer together, thereby, allowing more tracks per disk.
Reducing the size of the pit in which data is stored, facilitating greater number of pits per tract.
Creating the disk with multiple layers, thereby, logically increasing the number of surfaces per disk.
Variations of DVD include:
DVD-ROM: similar to CD-ROM
DVD- R: Similar to CD-R
DVD-RW: similar to CD-RW
Advantages
Very large storage capacity
Sound and picture quality is excellent, making them ideal for storing films with video and sound.
DVDs are now mass produced so they are relatively cheap
DVD players can read CDs
It is entirely unaffected by magnetic fields.
Disadvantages
DVDs do not work in CD drives
They can be easily damaged by breaking or scratching
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ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
FLASH MEMORY CARDS
A very popular non-volatile, rewritable memory chip, evolving from the
EPROM chip. Extremely durable, flash memory cards is widely used in digital
cameras, photo printers, PDA, cell phones, notebook and desktop
computers.
FLASH DRIVE
Flash memory storage devices are typically small, lightweight, removable and rewritable. They consist of a small
printed circuit board which is encased in plastic or metal casing. They usually have a
removable cap which covers and protects the part of the stick which is inserted into a USB
port.
Memory sticks are available from 125MB up to 32 GB.
Advantages
They are more compact and portable than floppy disks or CDs/DVDs.
They hold more data than a floppy disk and nowadays often more than a CD.
They are more reliable than a floppy disk because they have no moving parts
They are being developed with fashionable looking outer casings and are almost becoming a 'fashion
accessory' much in the way of a mobile phone.
Disadvantages
At the moment, the cost per megabyte of storage is more expensive than floppy disks, CDs or DVDs.
They can be easily lost
The metal part which is inserted into the USB port can be snapped off if they are handled roughly
TERMS ASSOCIATED WITH STORAGE DEVICES
Read/write head: is the mechanism that reads items and writes items to and from storage medium such as hard
drive and floppy disk.
Buffers: Instead of reading a single byte on request, the system reads a block consisting of an entire sector (or
more), and stores it in a buffer. Then when the next byte in the sector is needed, it is retrieved form the buffer,
instead of being read from the disk. This is much quicker than reading individual bytes from the disk. Buffering
is used in many types of transfer. Print outputs are usually sent to a buffer before reaching the printer, because
the printer and the CPU works at different speeds.
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ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
Access time: this measures the amount of time it takes a storage device to locate an item on a storage medium
and the time required to deliver an item from memory to the processor
See definition above for Tracks, Sectors, Cylinders, Sequential Access, Direct Access
DEVICE INTERFACE (SCSI, IDE, SATA)
IDE:
Acronym for Intelligent Drive Electronics or Integrated Drive Electronics. The IDE interface is an
interface for mass storage devices, in which the controller is integrated into the disk or CD-ROM drive.
SCSI:
Acronym for Serial Advanced Technology Attachment. It is a set of standards for physically connecting
and transferring data between computers and peripheral devices. SCSI is most commonly used for hard
disk and tape drives, but can connect a wide range of other devices, including scanners and CD drives.
SATA: Acronym for Small Computer System Interface. It is a computer bus primarily designs for transfer of
data between a computer and mass storage devices such as hard disk drives and optical drives.
FireWire: similar to the USB port in that it connects multiple types of devices that require fast data transmission
speeds such as digital cameras, Scanners, external hard drives.
UNITS OF STORAGE
The electronic nature of the computer makes it possible to combine the two digital states – on and off –
represent letters, numbers, colors, sounds, images and shapes. An “one” or “off” electronic state is represented
by a bit, short for binary digit. In the binary numbering system (base 2), the on bit is a 1 and the off-bit is a 0. A
byte is a combination of bits. A byte represents a character e.g. “B” = 1000010.
The capacity of RAM, cache and other memories are stated in terms of the number of bytes they can store.
Memory capacities for most computers are measured in Megabytes (MB) and Gigabytes (GB). Occasionally you
will see memory capacities of individual memory stated in terms of Kilobits (Kb) and Megabits (Mb).
Capacity
Storage Term
Bit
Byte
Kilobyte (KB)
Megabyte(MB)
Gigabyte (GB)
Terabyte(TB)
Created by: Ms. Yanecia Stewart (2009)
1 or 0
8 bits
1 thousand Bytes
1 Million Bytes
1Bilion Bytes
1 Trillion Bytes
Exact number of bytes
210 or 1,024
220 or 1,048,576
230 or 1,073,741,824
240 or 1,099,511,627,776
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Section 1: Fundaments of Hardware & Software
A Word describes the number of bits that are handled as a unit within a particular computer system bus or
during internal processing. The number of bits in a word is referred to as the word size. The Word Size for
internal processing for most modern PCs is 64 bits
Address: an identification of a unique number that identifies the location of a byte in memory.
Bi-stable device: a device which can exist in 2 discrete stable states either ‘on’ or ‘off’ and will remain in each
state until changed by a user. E.g. A light switch. It has the states “on” and “off”.
BINARY
Binary Conversion table
211
2048
210
1024
29
512
28
256
27
128
26
64
25
32
24
16
23
8
22
4
21
2
20
1
Binary Coding Scheme
ASCII: American Standard Code for Information Interchange. This code uses 7 bits to represent a character.
EBCDIC: Extended Binary Coded Decimal Interchange Code: Uses 8 bits to represent a character.
CONVERSION
FROM
DECIMAL
TO BINARY
A simple method is to divide the decimal number repetitively by 2 recording the remainder in
the next binary digit position, from bottom to top.
Question:
1.
2.
Convert 37 to its binary representation.
Convert 64 to its binary representation.
CONVERSION
FROM
BINARY
TO DECIMAL
Values represented in binary strings can be converted to their decimal equivalent by adding
the set decimal place values.
Question:
3.
4.
Convert 1001012 to its decimal equivalent. Answer =37
Convert 11111112 to its decimal equivalent. Answer =95
Created by: Ms. Yanecia Stewart (2009)
ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
ADDITION
OF BINARY
NUMBERS
Question:
5.
6.
7.
8.
9.
10.
11.
The rule for addition of binary numbers are as follows
0+0=0
1+0=1
0+1=1
1+1=0 carry 1
1+1+1=1 carry 1
Add 10010011+111101.
Give the binary value of 36+110011
What is the value of X in the following equation? X2-11011=11100110
What is the value of X in the following equation? 9210-X2=111001
In a certain coding scheme, the characters are stored in consecutive sequence. If
“&” is represented by 01001001, what is the representation of “$” if it is 8
consecutive spaces to the right of “&”.
In EBCDIC, the letters of the alphabet are stored using consecutive codes. If “C” is
represented by 11000101, what is the representation of “P”?
In ASCII, the letters of the alphabet are stored in consecutive codes. If “L” is
represented by 1001100, what is the representation of “B”?
CONVERTING
A NEGATIVE
DECIMAL
NUMBER TO
BINARY
USING SIGN &
MAGNITUDE
Steps:
1. Convert the decimal number to its binary value, ignoring the
negative sign.
2. Extend the bits to 8, by attaching 0s to the leftmost part of the bit
string.
3. Attach a 1 to the leftmost part of the bit string. The 1 is the sign bit;
it indicated that the number is negative. Alternatively, a 0 indicates
that the number is positive.
Question:
12.
Convert -37 to binary using the Sign & Magnitude method.
CONVERTING
A SIGN &
MAGNITUDE
NEGATIVE
NUMBER TO
DECIMAL
Steps:
1. Convert the binary number to its decimal value ignoring the leftmost
bit in your calculations
2. If the leftmost bit is a 1, then the number is negative. Place the
negative sign before the number.
Created by: Ms. Yanecia Stewart (2009)
ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
Question:
13.
Convert the Sign & Magnitude number 100100101 to decimal.
ONE’S
COMPLIMENT
To convert a binary number to its ones compliment representation you
change all the 1s to 0s and all 0s to 1s.
Question:
14.
Convert the binary number 1100110to its ones compliment value.
TWO’S
COMPLIMENT
The Twos compliment of a binary number is formed by first finding its ones
compliment and adding a one.
Question:
15.
Convert the binary number 1100110 to its twos compliment value.
CONVERTING
A NEGATIVE
NUMBER TO
DECIMAL
USING THE
TWOS
COMPLIMENT
Steps:
1. Convert the number to its binary value ignoring the sign.
2. Extend the bit string to 8, by attaching 0s to the leftmost part of the
bit string
3. Find the ones compliment
4. Find the twos Compliment.
Question:
16.
Convert -5 to its binary representation using the Twos compliment method.
CONVERTING
A BINARY
Steps:
1. Convert the binary number to its decimal equivalent, making the leftmost bit
Created by: Ms. Yanecia Stewart (2009)
ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
TWOS
COMPLIMENT
NUMBER TO
DECIMAL
(the sign bit) binary place value negative.
Question:
17.
11111011 is a Twos compliment binary number. Convert it to its decimal equivalent.
BINARY
CODED
DECIMAL
(BCD)
Numerical BCD Representation
0
0000
1
0001
2
0010
3
0011
4
0100
5
0101
6
0110
7
0111
8
1000
9
1001
Question:
18.
19.
Represent 9876 to BCD format
Convert the BCD 0010010010010101 number to its decimal value.
N.B Octal and decimal Numbering system will be done in class
SOFTWARE
Software is a program or set of instructions that controls the operation of a computer. Software falls into two
main categories
Application Software: also called Application Programs consist of programs designed to perform specific tasks
for users. Examples are Word-processing software such as Microsoft word, Spreadsheet software such as
Microsoft Excel and Accounting software such as Peachtree.
System Software: consist of programs that control the operations of the computer and its devices. E.g.
Operating System, Utility programs and translators
Created by: Ms. Yanecia Stewart (2009)
ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
APPLICATION SOFTWARE
Application programs can fall in the flowing categories
Custom Written Software: these are software packages that are written by the user or a software house under
contact to perform a specific task.
General Purpose Software: these are software packages that can be purchased off the shelves. These packages
are used for routine tasks. E.g. Microsoft Word.
Special Purpose Software Packages: These are software that can be purchased the shelves and are used to
perform specific tasks. E.g. Payroll package
Customization of General Purchase and Special Purpose Software Packages: It is possible for organization to
pay licensed owner of the general purpose or specific software packages to make changes to the existing
software packages in order to meet specific need of the organization.
SYSTEM SOFTWARE
Utility programs: A utility program is a type of system software that allows a user to perform maintenance-type
tasks for example
A disk cleanup utility searches for and removes unnecessary files.
Antivirus programs that runs in the background to remove viruses and malicious programs,
A backup utility allows users to copy files to another storage medium
A restore utility reverses the process and returns backed up files to their original form
A personal firewall detects and protects a personal computer from unauthorized intrusions
OPERATING SYSTEM
An operating system is a form of system software that coordinates all activities of the hardware devices in a
computer. The operating system also contains instructions that allow you to run application software.
Before a computer can run any application software, the operating system must first be loaded from the hard
disk into the computer memory. Each time you start your machine , the operating system is loaded or copied
into memory from the computer’s hard disk. Once the operating System is loaded, it tells the computer how to
perform instructions such as program instructions and transferring data among input and output devices and
memory. The Operating system which remains in memory while the computer is running allows you to
communicate with the computer and other software, such as application software. The Operating System
continues to run until the computer is turned off.
Examples of operating systems are: Windows XP, Windows 2000, Windows Vista, Mac OS, UNIX, Linux.
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ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
FILE MANAGEMENT
OS software actively manages the computer’s filing system. All data and instructions stored on the computer’s
secondary storage devices e.g. the hard drive, are contained in structure called FILES. It may be useful to note
that the files on the computer are similar in concept to the files found in filing cabinet. If I typed a letter on the
computer and wished to save it for future use, when I select a save command, the letter would be placed in a
file which I would have to name (e.g. MYLETTER) before it can be saved.
File management functions which the OS software makes available to the user include those for: copying files,
erasing files, moving files, renaming files, finding files, and displaying list of files stored and details (e.g. size, data
created) on those files. The OS also provides some file management functions, which are invisible to the user.
For example, it keeps track of the physical dish location of each file so that the user need only refer to them by
name (e.g. MY LETTER) when they need to use them in the future.
In addition, OS software allows users to manage disk by formatting them. Formatting is the process of preparing
a disk for reading and writing by organizing the disk into storage locations called tracks and sectors. Note disk
cannot be used if they are not formatted. It is important to also note that disk can be reformatted, and this has
the effect of erasing anything that was previously stored on the disk!
Further OS software also allows users to organize these disks into logical (not physical) sections called
directories/folders in the DOS and Windows OS respectively. Files are then stored within these
directories/folders so as to enable users and the OS itself to find files faster. Therefore if I want to use my
computer for storing some word documents, spreadsheet documents and games, I would create on my hard
drive the following folders/directories WORD DOCUMENTS, GAMES, and SPREADSHEETS. This
folders/directories can further be broken down into sub-directories/folders. These folders can store
corresponding files. Let us assume that you have 2 word documents (My Letter, My Cover-page) and 1 game
(Mortal Combat II) and 3 Spreadsheets (Student File, Employee Payroll, Time table).
This information can be represented in a Tree Structure
MEMORY MANAGEMENT
The purpose of memory management is to optimize the use of random access memory (RAM). RAM stores data
and instruction while the processor interprets and executes them. The operating system allocates, or assigns,
data and instruction to an area of memory while they are being processed. Then it carefully monitors the
Created by: Ms. Yanecia Stewart (2009)
ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
contents of memory. Finally the operating system releases these items from memory (frees up space to
accommodate other programs) when the processor no longer requires them.
SECURITY
The operating system can allow or deny user access to the entire computer system or just a part of it.
Information which is confidential or which we wish to protect from accidental damage or deletion can be
protected in this way. Specific security measures, such as username and password are often implemented to
protect against unauthorized user viewing system resources.
The operating system also records successful and unsuccessful attempts in a file. This allows the network
administrator to review who is using or attempting to use the computer.
DEVICE MANAGEMENT
Device management controls peripheral devices by sending them commands in their own proprietary language.
The software routine that knows how to deal with each device is called a "driver," and the OS requires drivers
for the peripherals attached to the computer. When a new peripheral is added, that device's driver is installed
into the operating system.
USER INTERFACE
You can interact with software through the user interface. That is, a user interface controls how you enter data
and instruction and how information Is displayed on the screen. Three types of user interfaces are command
line, menu driven and Graphical Operating systems often use a combination of these interfaces to define how a
user interacts with a computer.
N.B Refer to Types of Interface Topic for more details
PROCESS MANAGEMENT
In operating systems, process is defined as “A program in execution”. The operating system is responsible for
managing allocation of the processor between the different programs. The operating system determines the
order in which programs are sent to the CPU for processing, this activity is popularly referred to as scheduling.
Created by: Ms. Yanecia Stewart (2009)
ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
MULTITASKING, MULTIPROCESSING AND MULTIPROGRAMMING
Multitasking: This describes the operating system’s ability to execute two or more related task at the same
time. A group of cooperating task is executed simultaneously to achieve a common goal.
Multiprocessing: The ability of a computer to execute programs on two (2) or more processors simultaneously.
The program is distributed over several processors. Multiprocessing increases a computer’s processing speed.
Multiprogramming: The ability of a computer to execute two or more programs at the same times using ONE
CPU For example, you can be writing a letter, checking your email and listening to music at the same time.
PROCESSING MODES
Batch Processing System: There are some operating systems that allow the processing of programs in batches. A
number of programs are batched together and run as a group. In batch processing the transaction are stored
and updated at intervals for example weekly or monthly. This is usually done in some medium and large
computes. There is no interaction between the user and the computer while the program is being run.
Computers which do batch processing often operate at night. Batch processing is no longer popular, but is still
used in Payroll and some Utility bills.
Online Systems: as efficient as batch processing is, it is not always suitable since there is many occasions where
data needs to be processed quickly or shared among users. On line systems get data uploaded hourly, daily-whatever the business requirements are. For example ay master.
Real time systems: record transactions into the database immediately. One real time system are banks; you
withdraw from your checking account via the ATM. Your checking account immediately records that transaction
and lowers your balance. Another example is a Airline Reservation system, where a delay of even few seconds is
unacceptable. People are calling every second to make or cancel reservations on various flights, the operators
needs to know the instant when all seats are booked or when a seat becomes available.
Created by: Ms. Yanecia Stewart (2009)
ACRM Evening Institute
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Section 1: Fundaments of Hardware & Software
TYPES OF INTERFACE
A user interface is a method or a display that enables a user of a computer system to interact with an application
or system software. Listed below are a number of software and hardware user interfaces.
SOFTWARE INTERFACE
Command Driven Interfaces: Here commands are
entered from the keyboard E. g DOS commands.
disadvantage is that you would have to memorize
commands and their exact syntax.
The
the
Graphical User Interface: These display icons,
which are graphic images each of which represents a
processing activity. Each of the icons represents items to be
selected. GUI eliminates the need for users to memorize
and enter commands. Example Graphical Images in
Windows.
Menu Driven Interfaces: In menu driven interfaces,
commands are issued and operations initiated by making
selection from a menus. These menus usually have a hierarchy structure where menus are embedded within
menus. Example is the File Menu found in Microsoft Office
Software.
Pull-Down Menus: Here the menu is displayed as a vertical
list, which hangs from a horizontal bar.
Pop-Up Menu: here the menu is displayed as a window
and is detached from the menu bar.
HARDWARE INTERFACE
See input devices for Touch Screen, Braille keyboards and Sensors.
Created by: Ms. Yanecia Stewart (2009)
ACRM Evening Institute
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