Chapter 2

Hardware

PARTS OF COMPUTER

Types of computer

(Micro-computer)

Hardware

INPUT DEVICESMANUAL AND AUTOMATIC

Manual

KeyboardUsed to input data into the computer

Advantage• They are very common; all

computers have one and they are easy to use.

Disadvantage• Easy to make mistakes if you

can’t type quickly.Concept KeyboardA pictorial keyboard which you can press.

Advantage• Easy to use and waterproofDisadvantage• The screen can get dirty.• Might need to change the

pictures if your stock changes

Mouse Enables you to control the movement of the on screen curser by moving it around a surfaceAdvantage

Easy to learn to useAccurate for selecting things

DisadvantageNeed a flat space next to the computer.

Tracker BallLike an upside down mouse, you turn it with your hand to move the pointer on the screen

Advantage• Ideal for using when flat space

next to computer is limited

Disadvantage• Not supplied as standard.

JoystickSimilar to a tracker ball in operation except you have a stick which is moved rather than a rolling ball.

Advantage• Immediate feel of direction.

Disadvantage• Some people find them more

difficult to use than mice.

MicrophoneUsed to input soundAdvantages

Some systems can understand most peoples voices with voice recognition software

Disadvantages Some systems need to be trained to understand each different voice.

Digital CameraLooks very similar to a traditional camera.  However, unlike photographic cameras, digital cameras do not use film Advantage• No film needed.• Images can be digitally

manipulatedDisadvantage• Need to print out photographsScannerAnother way in which we can capture still images or text to be stored and used on a computer.  Advantage• Can input things from paper

documents• With OCR software, text can

be scanned in Disadvantage• Images can take up a lot of

memory space.

Graphics tablet Produces much more accurate drawings on the screen than a mouse or a pointing device could.Advantage

Effective method of creating or changing diagrams and images.

Disadvantage Only useful for inputting data about diagrams.Can be very sensitive to movement and difficult to get used to using

Automatic

MICRStands for Magnetic Ink Character Recognition. Banks use them; the reader reads the numbers on a cheque.Advantage• Read at 100% accuracy..

Disadvantage• The reader and ink is

expensiveOMR Stands for Optical Mark Reader. Reads pencil marks on a specially designed form or document, e.g. on a lottery ticket. Advantage

Fast and accurate way of inputting information.

DisadvantageOnly works if the marks have been made accurately and clearly.

OCR Stands for Optical Character Recognition. It enables the computer to identify written or printed characters which have been scanned in. Advantage

95% accurate

DisadvantageNeeds careful checking as letters can be misread.

Barcode ReaderA bar code reader uses a visible red light to scan and read the barcode.  The reflected light is translated into digital data that is interpreted by the computer and the correct price and product information is displayed.

Advantage• Any price change only needs

to be changed on the computer system, not on each item.

Magnetic Stripe Build into back of plastic cards, e.g. identity cards or credit cards. Holds information about the card owner.Advantage

Simple to use and cheap to produce.

DisadvantageLimited storage capacity – only 60 characters.Sensors

Sensors are used to detect physical quantities outside a computer such as temperature, pressure and light. 

To be able to process input from sensors a device called an analogue to digital converter must be connected between the computer and the sensors. This device converts signals from sensors into digital data that the computer can process

OUTPUT DEVICES

Output Once the computer has processed all the information from

the inputs then it must display or output the information in some way.

This is when we use Output devices that enable us to see or hear the information stored in the computer.

Output Devices

There are many different Output devices but the most commonly used are:

1. Monitors2. Printers3. Speakers / Headphones4. Lights5. Plotters

Monitors Monitors display the information on a screen.

You can get 2 main types of monitors: CRT’s: Cathode Ray Tube monitors are fairly

large and they are not as common as LCD’s nowadays. CRT’s work by using an electron gun situated at the end of the tube.

LCD’s: Liquid Crystal Display monitors are thin and are more commonly used. They work by using electronically charged crystals.

Printers There are 3 types of Printers:

Dot Matrix : This printer is the oldest of the three and is not used much now because it doesn’t give as good results as the other two. It uses Carbon ribbon and pins.

Ink Jets : This printer has become cheaper and is commonly used at home as they are perfect for small quantities of work. The ink jets use ink cartridges that are heated up and droplets are then dropped on to the paper forming a small part of the overall image.

Laser : This printer is more expensive that the others however it is excellent for use in work as it is quiet, quick, can be stocked with a lot of paper and produces high-quality work.

Plotters These devices produce high quality lines diagrams on

paper. Architects, Engineers and Scientist often use plotters.

The plotter uses a pen that can be lifted on and off the paper which is how this dev

Speakers / Headphones There is usually a small speaker within the computer

however to increase the volume and quality of the sound we plug in external speakers which allow us to hear the music better.

Headphones can be plugged into almost all computers and they enable you to listen to your music without disturbing others.

Lights These are known as LED’s (light emitting diodes) and

they are useful in presentations and also for situations like when a computer is controlling traffic lights.

LED’s last approx. 100,000 hours and they can either be dim or very bright.

Processor Technology

Central Processor Unit

Storage and MemoryDevices

STORAGE AND MEMORY

Unless you want to lose all of the work you have done on your computer, you need to have a way to store it safely.There are various types of storage

devices, different devices are suitable for different tasks.

We will be looking at the main ones which you need to know about.

HARDWAREHardware is the name given to

any part of a computer that you can

touch

~*~An individual piece of

hardware is called a device

ROM & RAMThe main memory of a computer

is made up of a set of memory chips called

ROM and RAM~*~

ROM = Read Only MemoryRAM = Random Access Memory

ROM RAM

The instructions to start the computer are stored on this

This sort of memory is non-volatile memory

Programs and data stored on RAM are lost when a computer is switched off-

This memory is volatile memory

Storage Devices Computer memory is measured in Bytes

Byte = 8 bits

Kilobyte = 1000 bytes

Megabyte = 1000 kilobytes

Gigabyte = 1000 Megabytes

Bit = either 0 or 1Units

The two main types

Main store ( memory storage in the computer) ~*~

Backing storage ( storage on disks tape CD etc)

Hard DiskAdvantages• Main Backing

storage for files and programs

• Can store lots of data compared to the floppy disc

• Can have a second hard disk as Back-up storage

Disadvantages• Slow to access

when compared to ram

• Data can Be damaged if the head crashes onto the platter

Typical size = 120GB

Floppy discAdvantages Small thin and

lightweight so easy to carry round

Can Be reused But data cant Be overwritten only deleted to create space

Disadvantages Can’t store that

much and one Big picture will take up a lot of room

It’s thin so it could get damaged easily

Typical size = 1·44 MB

Zip DiscAdvantages• Can hold more

data than a floppy disk and again easy to carry around Because of the size

Disadvantages• Much more

expensive than a floppy

• You need a special drive to read the disk

Typical size = 100 MB

Magnetic TapeAdvantages• Can store a lot of

data• Not easily

damaged• Can Be used

overnight to Back up a system

Disadvantages• Takes a long

time to load data onto it

• Have to go through the tape to get to the data you want – serial access

Typical size = 100MB

CD-RomAdvantages• Data cannot Be

erased – you cannot lose your data

• Easy to carry around

• Cheap to produce• Can Be read By a

DVD drive

Disadvantages• Fragile • Can scratch easily

– this effects the data when the laser reads it

• Slower to access than a hard drive

Typical size = 650mb

DVDAdvantages• large amount of

storage• Does not transmit

virus’s • The prices are

getting cheaper• Good for storing

films

Disadvantages• Doesn't work in CD

ROM drives• More expensive

than CD roms

Typical size = 5-17GB

Storing Data: Bits and Bytes

A Bit About Bits

Data: raw numbers, words, collections of unprocessed stuff…

Information: the organization of data into meaningful and useful terms.

A Bit About Bits In the world of computers, information

is digital. This information is made up of discrete

units. These discrete units are called: Bits. Bit: (Binary digit) is the smallest unit of

information a computer can process Bits have only two values: 1 or 0

A Bit About Bits

A collection of 8 bits is called a byte.

Bytes are bigger than bits.

A nibble is half of a byte (4 bits, this term is obsolete).

bit < nibble < byte

A Bit About Bits A collection of 8 bits can

represent 256 different messages:

28 = 256

By mixing and matching combinations of “On’s” and “Off’s” you can get 256 different messages.

A Bit About Bits

Binary Number System

128 64 32 16 8 4 2 1

= 0

128 64 32 16 8 4 2 1

= 1

128 64 32 16 8 4 2 1

= 2

128 64 32 16 8 4 2 1

= 3

128 64 32 16 8 4 2 1

= 255

Note: we get 256 possible characters because we start at 0 and go to 255 which is 256 separate numbers.

A Bit About Bits

ASCII (pronounced as-kee 2) is the most widely used code

To make words, sentences, and paragraphs fit into the computer’s binary-code circuitry, a unique piece of code was devised to represent each letter, digit, and special character as a unique string of bits.

A Bit About Bits American Standard Code

Using only 8 bits ASCII has a set of 256 individual characters, for all letters (upper and lower case), numbers and some special characters

Unicode is possibly going to replace ASCII. Unicode has a 65,000 character set. This will be done by using 2 bytes (16 bits) per character.

A Bit About Bits

Bits can represent data stored on a computer.

A string of bits can also represent an instruction 01101010 could tell the CPU to

add two numbers together.

A Bit About Bits B, KB, MB, GB, TB, PB

Those abbreviations describe the capacity of memory & storage components.

Also quantify the size of computer file.

Mb ≠ MB

A Bit about BitsTerm ValueByte A group of 8 bits.K (kilobyte) also KB

About 1000 bytes of information. Technically 1K is 1024, because 1024 is 210

MB (megabyte) Approximately 1000K, or 1 million bytes

GB (gigabyte) Approximately 1000MBTB (terabyte) Approximately 1 million

megabytes.