Grade_10 IT – Notes from M. Rootshtain
Module 2.1 The Computer
Definition- A computer is a multipurpose data processing
system which consists of hardware and software.
A. Hardware- This refers to the physical components of the
computer and is divided into two main groups.
a. Input- Devices used to enter data into the computer
e.g. keyboard.
b. Output- Devices that are used to receive data from the
computer e.g. monitor.
c. A third category consists of devices that are both
input and output. They too are divided into two
groups.
i. Storage devices e.g. hard drive
ii. Communication devices e.g. modem.
B. Software
Divided into two main categories.
a. System software - software used for the operation and
maintenance of the computer system e.g. the
operation system
b. Application Software- software designed to perform
one or more specific tasks for the user e.g. games
word processing etc.
c. In general terms the term data will apply to program
instructions, programs and data
i. Information is processed data.
ii data is unprocessed raw facts
iii Program instructions are electronically
executable data.
C. Processing – the IPO model (Input, Process, Output)
The basic model
The expanded model
Module 2.2 Hardware
Input devices
Keyboard
Mouse – Today we have a number of different types of mice.
o Serial PS2 (Port Serial Two, is green)
o USB (Universal Serial Bus)
o Infrared
In addition to the way the mouse connects to the computer
there are additional differences.
• Mechanical – Roller ball
• Optical
Please note that wireless mice need batteries and wired ones do
not.
Scanners - Scanners provide digital copies of documents of any
type. A scanner works by copying pixels from the document
and storing them digitally in the computer’s memory.
• The higher the resolution i.e. the more pixels (dots)
per inch the greater the required memory and
therefore the larger the stored file.
• Using colour increases the properties of each pixel
requiring even more memory and therefore larger
files.
• By decreasing resolution and using grayscale instead
of colour we reduce the size of the scanned file
dramatically.
• It is possible to scan documents into a word
processor for editing in order to achieve this instead
of copying pixels we use OCR (Optical Character
Recognition) software
N.B. Most scanners are supplied with programs
to scan images as well as with OCR software.
Digital Cameras – Unlike scanners digital cameras allow us to
capture real life objects and to store them digitally so that
they can be easily downloaded or uploaded to computing
devices. There are a number important factors that decide
the quality of a camera.
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Resolution – Typically 5-8 Mega Pixels (5-8 million
dots per square inch)
Storage – Cameras use a variety of stiffy disks (in
older cameras), memory cards and memory sticks
storing gigabytes worth of pictures.
Zoom – This refers to the ability to enlarge specific
parts of the image using software. The result is
usually less vivid and accurate than the original, this
is known as digital zoom and is of no real
importance,
and however optical zoom refers
to the normal zoom of traditional cameras and is the
more important of the two types.
Connectivity – are usually connected to the
computer using a USB port
Compression- most digital camera store in stored in
a file format called jpeg. Jpeg saves images by
compressing it. This causes smaller files but a
reduction in image quality.
Output devices
Printers
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Speed -this is measured in characters per second
(lines per minute (lpm) and pages per minute (ppm)
Replacement of consumables –Ribbons, Ink Cartridges and
toner Cartridges. NB. While it is much cheaper to refill
cartridges to purchase from the OEM (original equipment
manufacturer) this sometimes voids the warranty.
Resolution and print Quality. – is measured in dots per
inch and this is referred to the printer resolution.
Interface – most printers today connect using a USB port
Paper Size and Paper Tray
RAM – Because printers are much slower than the computer
itself, in order to avoid a bottle-neck, printers store the data
to be printed in their own RAM. Most modern Printers,
especially laser printers, have a minimum 48 MB RAM
Type of Printers
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Dot- Matrix printers – the print head consist of a
number of pins which strike a ribbon in order to print
a character on the paper. Print quality is usually poor.
Ink Jet printers – the print head is number of
nozzles and ink is sprayed in very fine droplets onto
the page. Speed is usually high and quality is good,
the running is silent but printing is costly. Printers,
however, are cheap.
Laser printers _-Same mechanism as photo copiers.
A drum is charged by the laser head. Tiny metal
finings (Toner) adhere to the drum. Paper passes over
the drum and the image is rolled onto it. The paper
then passes through a fuser unit which presses the
toner into the paper and bakes it into position>
Quality good, Speed high and printing costs are lower
than inkjet for monochrome. While prices have
dropped dramatically Lasers generally cost more
thank Inkjet Printers.
Both inkjet and lasers can print in color but color lasers are
very expensive to run.
Monitors
i. Types of Monitors - A monitor is an output device
which displays the results of instructions to the user.
There are three main types of monitors:
• CRT( Cathode Ray Tube)
• LCD(Liquid Crystal Display)
• A third type of Monitor technology called gas
plasma is growing popularity especially for
large flat screen TV’s used in homes and
businesses.
ii. Choosing a monitor
o Resolution – This is the number of pixels
which form a picture. Typical Resolutions are
800 by 600 or 1024 by 768. NB. Resolution is
dependant on the graphic card and the screen
o Size – screens are measured I inches from top
left corner to bottom right. Typical
measurements are 17, 19 and 21inches.
o Refresh Rate – because the phosphorous glow
fades it is necessary to refresh the image. The
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refresh is measured in Hertz .Interlaced
screens are poor quality with lower refresh
rates the screen compensates for this by
refreshing every alternate row on the way
down and the balance on the way up. If
Refresh rates are poor i.e. below 72 Hertz we
receive a flicker NB. LCD do not require
refreshing.
Graphic Card – Although not part of the
monitor the monitor’s performance is largely
affected by the capabilities of the graphic card.
Today most graphic cards have their own
processors and RAM (Minimum 128 MB) which
allows for 3-D graphics, high speed and
millions of colours.
Power Consumption and EMR (ElectroMagnetic Radiation) CRT monitors consume
large amounts of energy and their radiation
levels are governed by international
guidelines. LCD monitors have low power
consumptions and no radiation.
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Memory and Storage
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Memory vs. Storage
A. Storage - is long term and high capacity. It keeps data
and programs even after the computer has been
switched off. DVD writers, Hard drives etc., storage is
also known as second memory and is relatively slow.
a. Magnetic – hard disk drive (HDD), tape
cassettes / cartridges etc. very slow compared
to memory, high capacity.
b. Electronic – solid state drives, memory sticks,
memory cards etc. very fast compared to HDD
technology but slower than RAM. Medium
capacity.
c. Optical – CD / DVD / BluRay – low capacity and
very slow..
B. Memory – usually referred to as primary memory. It
holds much lower capacities but is considerably faster
memory is used to store data and instructions during
program execution
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ROM and RAM Primary Memory
A. Read only Memory (ROM)- This is non volatile
memory (data is retained even when there is no
power). It is Used to store programs which are
necessary for the starting up (booting ) of a computer
system e.g. The BIOS (Basic Input Output System)
B. RAM ( Random Access Memory) – RAM is faster than
ROM and the contents are continuously being
changed during operation. RAM is Volatile. There are
many different types of RAM but the main to groups
are S-RAM ( Static) D-RAM ( Dynamic). In most cases
the average entry level of the computer has 4 GB of
RAM and 500 GB of Storage.
Module 2.3 The Operating System
1. Definition – a collection of programmes designed to control
and manage the operation of a computer. It acts as an interface
between the user, hardware and software.
2. Functions of Operating SystemsA) Creating an interface for a usera) Command Line Interface (CLI)- all instructions
are typed in there are no brackets or icons
providing a small fast efficient environment but
very unfriendly
b) Graphic User Interface (GUI) - a typical example
is windows GUI’s are know as WIMP’s
(Windows,
,Icons ,Mouse and Pointer). GUI’s are very user
friendly but require large amounts of memory and
storage to operate efficiently. They also require a
high level of processing power from the CPU.
B) The operating system for:
a)allocating memory to specific programmes.
b) Assign CPU to each process
c) Allowing for the ordinary use of peripherals e.g.
printers, scanners etc.
d) Controlling all input and output to different
devices
e) Controlling all storage input and output i.e.
saving files, editing files reading files and deleting
files as well as renaming and moving.
C) Managing Processors – the OS schedules when and for
how long each different program will be processed by
the CPU in a multitasking or single tasking or multi-user
environment.
3. Open Source / Propriety SoftwareA) Windows
a) Windows is propriety software i.e. it has the
following characteristics
• It is owned and distributed by Microsoft
• Source Code is not available
• Each installation a license or licenses
• It involves costs per license
B) Linux – this is open source software and has the
following characteristics –
• Source code is available
• Users may change the code to suit their needs
• Either low cost or no cost.
• Different Installations do not require different
licenses.
• There is no real support except through user
groups.
C) Selling of software (distribution) - There are three
main methods for distribution
a) Shrink-wrap- normal retail software brought
usually in boxes which are cellophane wrapped
b) Shareware –Software that is distributed free for
users to try out if they are happy they pay a
nominal fee to the author to obtain
documentation , updates etc.
c)Freeware/Public Domain Software – software
that is free to distribute and use.
Software:
C. File Handling – the name of a file consists of the file name
and an extension. The extension generally designates the type
of file. Here are a few examples:
o doc- Microsoft Word Files (docx is a Microsoft Word
2007 file)
o xls- excel spreadsheet - xlsx
o mdb- Microsoft Access Data base. - accdb
o Wps- word perfect file.
o java – Java Application
2. System Software- includes all software which is used for the
management and maintenance of the computer system
A . Components of system software
a. drivers- it I s a small machine code program that allows an
operating system to control a specific device e.g. printer,
scanner , hard drive etc.
Each device will have different drivers for different operating
systems. This allows for the device to be able to function with a
wide variety of different operating systems. It acts as a
translator so that the operating system instructions can be
“understood” by the device.
b. utilities – these are programs that are divided into two main
areas.
i. Maintenance tools such as disk defragmenters , back
up software , disk scanning software , encryption and
compression software etc
ii. Security Utilities – Firewall , Anti –Virus
C. Programming languages
i. language levels –
• a high level language is a language that is close to human
language, e.g. Java ,Delphi ,c++ etc.
• low level is close to machine language (0’s and 1’s) e.g.
assembly.
ii. Translating for high level to machine code.