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Computer Systems - Computer Studies Form 1

Objectives

By the end of the lesson, you should be able to;

Define a computer system
State and explain the functional organization of the elements of a computer system

COMPUTER SYSTEMS

In this lesson, we shall learn more about input devices, central processing unit, output devices, secondary storage devices and setting up and cabling tasks.

Introduction


Objectives

By the end of the lesson you are expected to:

1. Define a computer system


2. State and explain the functional organization of the elements of a computer system


ASSESSMENT



What is a Computer System?

A system is a set of related components that interact together with an aim of achieving common goals.

A Computer system is composed of Hardware, Software and Liveware that interact to process data into information.

Components of a Computer system

The components include:

1. Hardware


2. Software


3. Liveware (computer user).

The components interact together to perform a task.


Hardware components

These are the physical devices of a computer system.

They consist of the mechanical, electrical and electronic parts which can be grouped as:

1. Input devices


2. Processing and memory devices

3 Output devices


4. Communication devices

examples of hardware components

Software components

These are programs that enable a computer system to perform a variety of tasks.

These programs are written in computer language.

They are further grouped as:

1. System software


2. Application software

The following are examples of system software:




Examples of software components include:

1. Microsoft office suit

  • - word
  • - excel
  • - access
  • - power point
  • - Frontpage
  • - Outlook express
2. Microsoft CorelDraw graphics suit

  • -Corel draw
  • -Corel paint
3. Adobe Creative Suite

  • -Photoshop
  • -llustrator
  • -In-design
  • -Dreamweaver
  • -Flash
  • -Fireworks

  Livewire Components

These are computer users. The users vary according to training and areas of specialisation. Liveware is also referred to as Orgware.

Examples of liveware include:

1. Computer operators


2. Computer technicians


3. Computer programmers


4. Database administrators


5. Network administrators


Input devices capture and convert human-readable data into a computer readable form. The human-readable form may be words like the ones in these sentences. Computer readable form consists of binary 0s and 1s.

Input devices are classified into five categories according to the way and type of data they capture. The categories are:


1. Keying devices


2. Pointing devices


3. Scanning devices


4. Speech recognition devices


5. Digital devices


LESSON OBJECTIVES

By the end of the lesson, you are expected to;

  1. describe keying input devices
  2. describe pointing input devices
  3. describe scanning input devices
  4. describe speech recognition input devices
  5. describe digital input devices.

 INPUT DEVICES

Input devices refer to the entry point to the computer. Input devices are classified as keying devices, pointing devices and scanning devices.

KEYING DEVICES

A keying device is used for typing letters, numbers and symbols as a means of entering data and commands into the computer. Examples of keying input devices are keyboards and keypads. Keypads are buttons arranged in a block which usually bear digits and other symbols but not a complete set of alphabetical letters. They are found on calculators, ATMs, Microwaves and other electronic devices.



POINTING DEVICES

Pointing devices control the position of the cursor or pointer on the screen and allow the user to control or select objects on the screen. Examples include :

Mouse

You are most probably familiar with the mouse. It is a device that is moved on a flat surface to direct and control a pointer on the computer display screen.

Trackball

A trackball is a movable ball on top of a stationary device that is rotated with the fingers or palm of the hand. (also refered to as trackerball)

A trackball may appear on the keyboard of portable computers. In some cases, it may be built into the right side of the screen.

Trackball

Joystick

A joystick consists of a vertical handle like a shaft lever mounted on a base with one or two buttons.It is operated by tilting the joystick to the corresponding direction of the cursor motion.Joy sticks are mainly used in video games, computer aided designs and computerized robot systems. Special joysticks maybe used by people with special needs.

Touchpad

Touchpad is a small flat surface over which to slide the finger, using the same movement as you would with a mouse. Many portable computers and desktop computers now include touchpad built into the keyboard.

A notebook's touchpad

Light Pen

A light pen is a light-sensitive pen-like device, connected by a wire to the computer. The pen has a photo sensor at the tip, that responds to the light emitted from the screen. They are used by engineers, graphic designers and illustrators to draw accurately.

Digitizing Tablets

A digitizing tablet consists of a tablet connected to a pen-like device with which the user sketches and draws images. The tablet contains electronics that enable it detect movement of the cursor or pen and translates the movements into a signal that is send to the computer. It enables the user to do shadings similar to those artists achieve using a pencil, pen or paint. They are used in graphic design, computer animation and engineering.

Pen-Based Systems

Pen-based computer systems use pen-like devices to enter handwriting and marks into a computer.

Smart Boards

It is a large touch-controlled screen that works with projector and a computer. The projector throws the computer's desktop image onto the interative white board which acts both as an output and input device. A user can write on a smartBoard using digital ink or by using a finger to control computer application by pointing, clicking and draging.

Smart boards are also used to show video clips and when one wants to practice handwriting.

Practice Exercise

1.From the following list, select by placing a tick next to the devices that are considered non-keyboard source data entry devices

a. Voice-Recognition devices

b. Video input devices

c. Light pen devices

d. Digitizing tablets


2.List three types of scanning devices

Answers

1 a. Voice-Recognition devices 

b. Video input devices 

c. Light pen devices

d. Digitizing tablets

2 a. Optical Mark Readers

b. Image Scanners

c. Optical Character Reader

d. Magnetic Ink Character Reader

SCANNING DEVICES

Scanning devices translate hardcopy images of text, graphics, objectsand photos into digital format which can be processed, stored, displayed and transfered to another a computer or device.

Bar Code Readers

Bar code readers are scanners that translate bar code symbols (vertical zebra-striped marks you see on most manufactured retail products) into digital form. They are commonly used in retail outlets such as supermarkets and bookshops.

Magnetic-ink Character Recognition (MICR)

MICR translate magnetic ink into digitized signal. Mainly used in the banks to read numbers printed at the bottom of bank checks and deposit slips. This magnetic ink contains iron-oxide which can be charged and read by this device.

Optical Mark Readers (OMR)

OMR read pencil marks and soft pens .they convert them into computer readable form. They are used to mark multiple choice exams.

Optical Character Readers (OCR)

OCR reads characters and converts them into machine-readable form. e.g. used to read utility bills such water and electricity consumption bills, handwritten, typed and printed text.

Image Scanners

Image scanners convert text, drawings, objects and photographs into a digital form that can be stored in a computer.

PRACTICAL EXERCISE



SPEECH RECOGNITION DEVICES

voice recognition devices

These devices convert a person's speech into a digital form then compares the pattern produced by the user with a set of pre-recorded pattern. When a match occurs the command is executed.

Audio input devices

These devices are useful for inputting data in situations in which people are unable to use their hands or need their hands free for other purposes. For example, blind and paralyzed people can give verbal commands to their computers rather than use the keyboard.


A System with digital devices

Definition

An input device is any peripheral used to convert data from human readable to computer readable form and enter into a computer.

DIGITAL DEVICES

Digital cameras

Digital cameras are devices that capture images and convert them into digital form that can be transmitted directly to a computer hard disk for manipulation, storage and printing.

The Central processing unit (CPU) controls and manipulates data to produce information. In a microcomputer the CPU is usually contained on a single integrated circuit or chip called a microprocessor. The CPU is the brain of the computer.

The CPU consists of the following:

1. Control unit (CU)


2. Arithmetic logic unit (ALU) and


3. Main Memory.


LESSON OBJECTIVES

By the end of the lesson, you are expected to:


1. Describe the control unit


2. Describe arithmetic and logic unit


3. Describe memory


4. Describe processors.


CENTRAL PROCESSING UNIT (CPU)

The central processing unit inclides control unit, Arithmatic unit, Registers, Main memory and Processors.

A microprocessor

CONTROL UNIT (CU)

-

Control unit is part of the CPU that performs the following functions:


1. Instructs the computer system on how to carry out a programs' instructions


2. Directs the movements of electronic signals between main memory and the Arithmetic and Logic Unit

3. Directs signals between main memory and input/output devices

ARITHMETIC AND LOGIC UNIT (ALU)

ALU is a portion of the central processor that performs arithmetic operations and logical operations.

It also controls the speed of those operations. Examples of arithmetic operations are; addition,subtraction,multiplication and division. while logical operations are such as comparisons (greater than, equal to, less than, not equal to).

REGISTERS

The Control Unit and ALU contain registers. Registers are high-speed storage locations that temporarily store data during processing and provide working areas for computation. They hold material that is to be processed immediately.

MAIN MEMORY

The main memory, which is also called primary storage, internal memory or Random Access Memory (RAM) is the working space in a computer.

The main memory has three functions:


1. It holds data for processing


2. It holds instructions (programs) for processing the data


3. It holds information waiting to be sent to an output device or secondary storage

The main memory is volatile ( i. e the contents are lost when the computer is switched off). The size of the main memory determines the volume of data that can be processed at once and the size of a program that may be used to process data.

RAM chip

Processing Speeds

The speed at which the processor executes instructions is called clock speed. The system clock controls how fast all operations take place. The faster the clock the faster the processing. The processor speeds are measured in megahertz (MHz). 1 MHz equal to 1 million beats (machines cycles) per second.


Types of Processors

There has been a remarkable growth in processing capability and clock speed of processors. There are three common types of processors, namely;


1. The Intel Family (Intel 8086 and 8088, Intel 80836, Intel 80846, Intel 80286, Intel Pentium, Intel Celeron)


2. The Advanced Micro Devices computer processor (AMD)


3. The Cyrix

Intel 80836

 

 

Intel 80286

Output devices convert machine-readable data that has been processed into human readable form. Output devices can be categorized into two groups; softcopy and hardcopy output devices.

Softcopy output devices produce output that is temporary and intangible while hardcopy output devices produce output that is permanent and tangible.





LESSON OBJECTIVES

By the end of the lesson, you are expected to:

1. describe softcopy output devices


2. describe hardcopy output devices

Exercise


Output Devices

These are the communications points from the computer

They are classified as softy copy and hardcopy devices.

SOFTCOPY OUTPUT DEVICES

These devices produce intangible output. They include monitors, speakers, projectors and LED.

MONITORS

A computer monitor may also be called a screen or Visual Display Unit (VDU).The monitor on your computer is an output unit converting computer data into human readable form. This makes it one of the communicating link between you and the information in your computer.

Like conventional TV screens, computer monitors are measured diagonally from corner to corner.

Screen Resolution

Screen resolution is a measure of the clarity of the computer display and is usually expressed in pixel. A pixel (picture element) is the smallest dot that can be displayed on a monitor.Low resolution gives unclear text and graphics as a result of small number of pixels used to form the picture. High resolution gives greater clarity and sharpness by displaying text and graphics using many pixels.

High resolution display

Some graphic standards for screen resolutions include:

1. Video Graphics Adaptor (VGA)640 X 480 pixels


2. Super Video Graphics Adaptor (SVGA)from 800 - 1280 X 600 -1024 pixels

A high resolutions (e.g. SVGA 1280 X 1024 pixels) will result in a smoother appearance for both text and graphics. However, the text and graphics will appear smaller on a monitor with a lower resolution (e.g. VGA 640 X 480 pixels)

Low resolution display

Types of Monitors

Monitors are classified into two main types according to display colour (coloured or monochrome) and technology

Cathode Ray Tubes (CRTs)

It is a common type of displays similar to standard television set.The inside of the screen is coated with phosphorescent material. An electron beam strikes this surface, exciting the phosphors and causing them to glow.

Some disadvantages of CRTs are:

1. They are heavy


2. They consume a lot of power


3. They occupy a large space


Flat Panels

Flat panel displays consist of two glass plates separated by a substance that may be activated in a particular way. Flat panel displays are classified into two:


1. Liquid crystal display (LCD): - As the name suggests, it uses liquid crystals which change their appearence when an electric current is passed through them.


2. Plasma Display:- Light is created by a plasma discharge from phosphor between two flat panels of glass.

Advantages of flat panels:

1. They are comfortable to use


2.They are portable


3. They consume less power as compared to CRTs.

SOUND OUTPUT

These devices produce digitized sounds ranging from beeps and chirps to music. Output is usually produced through on-board or external speakers.

VOICE OUTPUT DEVICES

These devices convert digital data into speech like sound. These devices are becoming popular, for example, in mobile phones you have probably heard (The mobile subscriber cannot be reached) or (The number you have called cannot be completed at the moment)

PROJECTORS

These devices are used to show information appearing on a computer screen onto a vertical screen for easier viewing. It is popular for presentations to large groups of people.Here is an example of an LCD projector

HARDCOPY OUTPUT DEVICES

These devices produce tangible output. They include printers, plotters and microfilm/microfiche.

PRINTERS

Printers are output devices that convert computer data into printed characters or graphics on paper. It is one of the most commonly used peripheral devices in general business. Printers can be categorized into two groups: Impact printers and Non-impact printers.

Printers are classified according to either mode of printing or speed of printing.

1. mode of printing

- this depends on the printing mechanisms i,e impact or non-impact.

IMPACT PRINTERS

Impact printers have a carbon ribbon and characters are (hammered) onto paper through the carbon ribbon, just like with a typewriter. Examples include dot matrix, chain printers, drum printers, golf ball and daisy wheel printers.

Dot-matrix printer

These printers have lines of pins programmed to hammer carbon ribbon onto paper to make a dot. This is a noisy and a slow process and produces low quality text and graphic output. With addition of a colour ribbon, colour output can be achieved.

NON-IMPACT PRINTERS

Non impact printers form characters and images without direct physical contact between the printing mechanism and the paper. Examples of non impact printers include ink-jet, laser and thermal.

Ink-jet Printers

An ink-jet or bubble printer form images with little dots. They spray small electrically charged drop lets of ink from nozzles through holes in a matrix at a high speed onto paper.

They can produce inexpensive colour output, are quiet and less expensive.

Laser Printers

Like dot matrix, laser printers create images with dots. These images are created on a drum with magnetically charged ink-like toner (powder) then transferred from drum to paper. They are popular because they produce clear images of both text and graphics, are quiet and very fast however they are expensive.

Thermal Printers

It is a character printer that provide character prints using the principle of heat. They use special print papers that senses the heated head character images which are then passed onto the papers as character prints.


2. Speed of printing

This include from the slowest to the fastest.

1. The character printers - they print one character at a time, e.g. the dot matrix printers.


2. The line printers - they print a line at a time, e.g. Ink jet printers.


3. The page printers - they print a whole page at a time, e.g. laser printers.


Plotters

This is a specialized output device designed to produce high quality graphics in a variety of colours. They are used for creating large hardcopy items such as maps and architectural drawings.

There are two main types of plotters:

1. Flatbed


2. Drum

A flatbed has a flat board which supports the paper on which a drawing is made. Drum plotters use a roll of paper which is mounted on a drum that can rotate.

Drum Plotter

Flatbed Plotter

As you have learned in the previous lesson, the data you are working on is stored in RAM (primary memory). Because RAM is volatile, data in it disappears when the power to the computer is turned off. Therefore, if you want to store data and programs permanently (until they are erased) you must save it onto a secondary storage device.

When information is read from a secondary storage, it is copied from the storage device to RAM. You have probably heard the phrases loading a program or opening a file to describe retrieving information from a secondary storage. The action of saving a file involves writing to a storage device. The computer mechanism that makes reading and writing possible is called a drive. Drives are designed to work with specific types of storage devices.

Secondary storage devices come in different types and sizes. They are classified according to the media used to make them as follows:

1. Magnetic tapes


2. Magnetic disks


3. Optical disks


4. Flash memory


LESSON OBJECTIVES

By the end of the lesson, you are expected to:

1. describe magnetic tapes

2. describe magnetic disks

3. describe optical disks

4. describe flash disks

Practice Exercise


 Secondary Storage devices

Secondary storage devices include tapes, Disks, Optica Disks and hard disks.

MAGNETIC TAPES

Magnetic tapes are thin plastic tapes that have been coated with a magnetic substance for storing data. The tapes were commonly used as secondary storage media for large computer systems. Nowadays they are mainly used to provide backup or duplication storage and in archiving of data.

Magnetic tapes are not very popular because accessing data on tapes is usually slow because data is stored serially i.e one after the other.

There are two different types of magnetic tapes namely:

1. Magnetic tape units (reels) used with large computers


2. Cartridge tape units (tape streamers) used with large computers and microcomputers

Magnetic Tape Reel

Cartridge Tape Unit

ACTIVITY

Taking Care of Diskettes

Diskettes are very delicate and therefore must be handled with care.


Practice exercise



MAGNETIC DISKS

Magnetic disks are secondary storage medium that allow data to be held as magnetized spots on a platter. They are the most commonly used storage devices. They come in two different types; diskettes and hard disks.

Diskettes

A diskette or floppy disk is a removable, round, flat piece of plastic that stores data and programs as magnetized spots. They are called floppy because they are made of a material that is flexible.

Diskettes come in different sizes: 3 1/2 inches which is the most common type, micro disks, 8 inches, 51/4 inches which are almost obsolete.


3" floppy diskette

5 1/4" floppy diskettes

8" floppy diskette

Characteristics of diskettes

Diskettes have the following characteristics:

Tracks and sectors: On diskettes data is recorded on concentric rings called tracks. Each track is divided into invisible wedge-shaped sections called sectors which are used by the computer for storage reference purposes. The number of sectors on the diskette vary according to the number of bits per inch (recording density). Each sector holds 512 bytes of data (1 byte is equivalent to 1 character).

Write-protect features: Diskettes have features to prevent someone from accidentally writing over data on the diskette or making changes to program and data files. To write-protect your diskette, you press a lever toward the edge of the diskette, uncovering a hole which appears on the lower right side, when viewed from the back.

Data density: Not all diskettes hold the same amount of data. A diskettes capacity depends on its recording density (the number of bits per inch that can be written onto the surface of the diskette. Today most diskettes are high-density (HD) and can store upto 1.44 MB (Mega Bytes).

Formatting diskettes: Formatting means preparing a diskette to make it ready for use by creating tracks and sectors. Formatting also erases the contents of the diskette.

HARD DISKS

Hard disks are thin, rigid metal or glass platters covered with a substance that allows data to be held on magnetized spots. They are usually tightly sealed within an enclosed unit to prevent any foreign matter such as dust or smoke particles from getting inside.

Hard disks come in three categories; internal, external and removable hard disks

Internal hard disks

Internal hard disks are sealed inside a hard disk drive that is built into the system unit and cannot be removed. They are also refered to as fixed hard disks.


PRACTICAL EXERCISE







OPTICAL DISKS

Optical disks are removable disks on which data is written and read through the use of laser beams.

The most familiar form of optical disk is the one used in the music industry. The optical disk technology has revolutionized the music business with compact disks (CDs) and the computer industry with a form of secondary storage.

CDs may hold 650 MB of data or more. A 650 MB CD can hold 250,000 pages of text, or more than 7000 photos or graphics or 19 hours of speech or 74 minutes of video.

Optical disks used with computers include the following;


1. Compact disks Read Only Memory(CD-ROM), Digital Versatile disks - ROMs(DVD-ROM).


2. CD-RW (Rewriteable)


3. CD-R (Recordable), DVD-R


OPTICAL DISKS

Optical disks are removable disks on which data is written and read through the use of laser beams.


The most familiar form of optical disk is the one used in the music industry.The optical disk technology has revolutionized the music business with compact disks (CDs) and the computer industry with a form of secondary storage.

CDs may hold 650 MB of data or more. A 650 MB CD can hold 250,000 pages of text, or more than 7000 photos or graphics or 19 hours of speech or 74 minutes of video.

Optical disks used with computers consist of these main types:


1. Compact disks (CDs)


2. Digital Versatile disks (DVDs)


COMPACT DISKS

CDs has the following types:


1. CD-ROM disks


2. CD-R disks


3. CD-RW disks

CD-ROM disk

CD-ROM stands for Compact disk Read Only Memory. It is an optical disk format used to hold data and software such as prerecorded text, graphics and sound. The contents of CD-ROM are recorded at the time of manufacture and cannot be written or erased by the user. This feature makes CD-ROMs excellent media for software distribution.

Types of CDs

1) CD-R DISKS

CD-R stands for Compact disk recordable. It is a CD format that allows users with CD-R drives to write data only once onto a specially manufactured disk that can then be read by a standard CD-ROM drive. Once the data is recorded, it cannot be written over (changed).

2) CD-RW disks

CD-RW stands for Compact disk rewritable. It is a CD format that allows users to erase data so that the disk can be used over and over again.

DIGITAL VERSATILE DISKS (DVDS)

DVDs have more storage capacity, faster data transfer rate, deliver high quality pictures and sounds as compared to CDs. DVDs has the following types: DVD-ROM disks, DVD-R disks and DVD-RW disks.

1) DVD-ROM disks

This is a DVD format used to hold data and software such as prerecorded text, graphics and sound. The contents of DVD-ROM are recorded at the time of manufacture and cannot be written or erased by the user.

2) DVD-R disks

This is a DVD format that allows users with DVD-R drives to write data only once onto a specially manufactured disk that can then be read by a standard DVD-ROM drive. Once the data is recorded, it cannot be written over (changed).

3) DVD-RW disks

This is a DVD format that allows users to erase data so that the disk can be used over and over again.

FLASH MEMORIES

Flash memories are compact,flexible type of storage.They are a variation of computer memory chips that are used to simulate main memory and to supplement or replace hard disk drives for permanent data storage.

Hard Disks

Hard disks are thin rigid metal or glass platers covered with a substance that allows data to be held on magnetised spots. They are usually tightly sealed within an enclosed unit to prevent any foreign matter such as dust or smoke particles from getting inside.


External hard disks

If you dont have room in the system unit for another internal hard disk but need additional storage, then you can use an external hard disk that can be connected to the computer the same way you would connect any peripheral device.

HARD DISKS

Removable hard disks

Removable hard disks (hard disk cartridges) consist of one or more platters enclosed along with the read/write heads in a hard plastic case. This case is inserted into a drive connected to the computer. Examples of removable hard disks include; jaz cartridges which can hold 2 GB or more and zip cartridges which can hold more than 100 MB.

 

LESSON OBJECTIVES

By the end of the lesson, you are expected to:

1. Describe types of cables
2. Describe types of ports

3. Describe basic computer set up and cabling

 

Exercise



 Basic Computer Set up and Cabling

In this lesson, we shall learn more about types of cables, power cables, interface or Data cables and connections

Connecting Computer Components

Factors to consider before assembling a computer:

Switch off main power supply and disconnect all cables .

Ensure you have all the necessary tools i.e a set of screw drivers, electrical pliers etc.

Have the installation manual at hand

Do not work without supervision or guidance

When assembling a computer, there are a number of things that you should never do:

  1. Force cables into ports
  2. Touch exposed electronic part
  3. Change the voltage ratings from 240V to any other.
  4. never work alone in case of any emergency.

Things that you should do

  1. Follow the instructions from the manual.
  2. All the connections must be firm e.g power cables
  3. Discharge static electric from your body by wearing anti-static wrist member.

Types of Cables

Cables are divided into two broad categories namely:

1. Power cables


2. Interface cables.

Interface/Data cables and Ports

There are three types of interface cables and ports namely:


1. Parallel Cables


2. Serial Cables


3. Universal Serial Board (USB)

Parallel Cables and Ports

Parallel cables transmit data/information simultaneously i.e. they transmit 8 bits at the same time. The main advantage of these cables is that they transmit data faster than serial cables. They are mainly used for connecting printers and removable storage drives e.g. zip drives.

Parallel ports connect parallel cables to the motherboard. A parallel port has 25 holes. This type of port is known as a female connector. A computer internally labels each parallel port with the letters LPT. The first parallel port is named LPT1, the second parallel port is named LPT2, and so on.

Example of a Parallel port

 

Serial Cables and Ports

Serial cables transmit data/information one bit at a time. They are slower than parallel cables but more reliable. They are used to connect devices such as mice, keyboard and serial printers.

A serial port has either 9 or 25 pins. This type of port is known as a male connector. The computer internally labels each serial port the letters COM. The first serial port is named COM1, the second serial port is named COM2, and so on.

Example of a Serial port

Universal Serial Bus (USB) cables and Ports

USB is a multi purpose type of port that allows one to connect up to 127 devices using only one port. For example, you can use the same port to connect a printer, joystick, scanner, mouse and keyboard to your computer. other advantages of USB ports are:

1. The transmission of data is fast


2. It is a plug and play (PnP) compliant.

USB Port

USB Cable


Fire wire

Fire wire is a high speed low cost serial bus system designed to provide efficient transfer of data between a peripheral device and a computer.

It allows camcorders, scanners, disk drives, DVD players, CDROMS and printers to share a common connecting bus.

1. It is a high speed serial bus that supports more than 63 devices


2. Fully supported by Windows 98 onwards

Fire Wire Cable

INFRARED (IrDA) Ports

These are data transfer ports that use wireless technology for connecting devices such as keyboards, mice and printers. This type of connection uses a certain frequency of radio waves to transmit data and it requires an unobstructed line of sight between the transmitter and the receiver.

Small Computer System Interface (SCSI) Port

This port and interface cables transmit data in parallel but are faster than parallel cables.

SCSI port allows connection of more than 8 peripheral devices linked together in what is called a daisy chain along an extended cable. These devices include external hard disk drives, magnetic tape units, scanners and CD-ROM drives.

6-Pin/PS-2 ports

Earlier computers used the 5 pin DIN for connecting the keyboards but this has now been replaced by the 6 pin mini DIN known as PS-2

5-Pin DIN cable

6-Pin port

Monitor (Video Adapter) Ports

These ports are used to connect the monitor to the video adapter card inside the system unit. The two most common connectors used for monitors are the 9 pin D and the 15 pin D. The pins must be compatible with the number of holes in the video adapter card.

Power cables

These cables supply power to the computer's power supply unit. From the power supply unit, electric current is converted from Alternating current (A.C) to Direct current (D.C) then redistributed to other internal devices

power cable


power supply unit

Interface/Data cables

These are wires which connect the peripheral devices to the motherboard through ports. The interface cables transmit data signals.

A port is a socket on the motherboard that is connected by a bus to peripheral devices such as a monitor or a printer so that it can communicate with the computer system.

Connecting basic computer peripherals

The following rules should be observed before you carry out setup activity:


1. Disconnect all devices from power


2. Discharge static electricity that might have built up on the hands by touching an earthed metallic object or wearing an anti-static wrist strap.

Parallel cable

Serial cable


USB cable




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