Computer Hardware docx

MAIN MEMORY - ROM and RAM • ROM is Read Only Memory • Data stored in ROM can only be read, it can never be written over or deleted.. It is where most programs and data are stored while

Computer Hardware

Hardware and Software

• Hardware refers to all the parts of the Computer System that we can touch.

joysticks, printers, processors etc.

• Software refers to all the programs and data that we use with the computer.

• A computer is an information processing machine.

• A computer only follows the instructions it

is given.

• Data is Input, Processed and then Output.

What is a Computer?

I’m ONLY a machine!

» Very powerful computers able to process 1000’s

of times more information a second than PCs

Smallest

Biggest

IPO - Input, Process, Output

Data is INPUT into the computer

system

It is then PROCESSED to produce

useful Information as OUTPUT.

Data and Information

Data has no meaning

• Data is made up of symbols e.g.

871652; H789 IOS; £76.91

Information has a meaning

• We understand what a piece of information

is about e.g

Telephone Number: 871652

Car License Plate: H789 IOS

More Input, Process, Output

• Data is the RAW MATERIAL.

• This raw material is processed.

• When the processing is completed a useful thing is produced…INFORMATION

Computer - Block Diagram

• The Computer System consists of four

Devices Central Processing Unit (CPU) Devices Output

The central processing

unit (CPU)

This is the part of the computer where the searching and sorting of data, calculating and decision-making goes on

The CPU contains the processor [ Control Unit and the Arithmetic and Logic Unit (ALU) ] and the Main Memory

The Processor

• The CONTROL UNIT fetches program instructions from the memory storage

locations, decodes and then executes them.

• The ALU (Arithmetic/Logic Unit) carries out all the calculations as instructed by the control unit.

MAIN MEMORY - ROM and RAM

• ROM is Read Only Memory

• Data stored in ROM can only be read, it can never be

written over or deleted We normally store important programs in ROM to do with the computers Operating System (see later) NON VOLATILE MEMORY

• RAM is Random Access Memory

• It can be written to and read from It is where most

programs and data are stored while the

computer is being used RAM loses its contents when

the computer is switched off VOLATILE

MEMORY

PROCESSOR

Data Flow

• Computers store blocks of data called

‘words’ in memory (A 32 bit computer has words that are 32 bits long).

• Each place that can store a word is called a

storage location.

• Each storage location has a unique address

that identifies it from all the other locations.

Machine Code

• Computers only understand binary!!!

• All programs have to end up in binary language in order work

• The binary language that the computer

• Machine code looks like this…

00100111,01110100,10010001

Bits and Bytes [BINARY]

• Each 1 or 0 is called a BIT (short for Binary Digit)

• Eight bits are called a BYTE.

• 1024 bytes is a KILOBYTE (Kb for short)

• 1024 kilobytes is a MEGABYTE (Mb for short)

• 1024 megabytes is a GIGABYTE (Gb for short)

These units are used to measure the size of storage or storage requirements e.g the available memory, hard disk space,

program size.

Bits and Bytes [BINARY]

Binary Everywhere!

• Binary is used to store all the data and

programs in a computer system.

• We use binary to store:

Graphics, Text, Numbers, Video, Sound and Programs.

• Binary is just the code used to store the

data

• You don’t need to understand binary (that’s

Maths) but you do need to know that it is how most numbers are stored in the computer

Storing Graphics

• Black and White graphics are stored using pixels

( Picture Elements ).

• The image to be stored is broken up into dots,

each dot is a pixel.

• The pixels are ON for black and OFF for white e.g.

Hardware Devices

• Devices are either INPUT , OUTPUT or

BACKING STORAGE

• Input devices allow us to enter data into the

computer system (mouse, microphone etc).

• Output devices allow us to receive information from the computer system (monitor, speakers, robot).

• Backing storage devices allow us to store programs and data so that we can use them later (floppy

disc, magnetic tape, CD-ROM).

• Backing storage is used to store programs and data when they are not being used or when a computer is switched off

• When programs and data are needed they are copied into main memory but also still remain on backing storage

• Magnetic tape drives, floppy disk drives and hard disk drives are all examples of backing storage devices

• WORM - Write Once Read Many

A WORM is a writable optical disc An optical disc is any disc that can be read using light (normally laser light)

WORM drives use a high powered laser to burn the data into the disc This can then be read in the same way that CD-ROM's are read Because the data is burnt onto the disc each disc can only be written once and the data written is permanent.

and CD-ROM are all types of

backing storage.

Backing Storage Devices

PROM and EPROM

• PROM and EPROM are both special types of

programmable read only memory

• PROM stands for Programmable Read Only

Memory This type of memory can be

programmed once but can’t be changed again afterwards

• EPROM stands for Erasable Programmable

Read Only Memory This type of memory can be programmed and then changed whenever

necessary

• A floppy disc can be used to save data.

• It can also be used to make a backup copy of

small files.

• A backup is a second copy of your data that you take in case something happens to the original.

• You should always make a backup of important files.

Write Protect Tab Disc Label

The Floppy Disk

• Capacity : 1.44 Mb

Formatting A Floppy Disk

The formatting process involves:

 Dividing the surface of the disk into invisible

circles called tracks and sectors

 Setting up a root directory where the list of

files that are on the disk will be kept

 Data on a magnetic disk is located by finding the

address of its location from an index in the root

directory

 Each address in the index contains a track and sector number for an individual data segment

Formatting A Floppy Disk

Tracks

Index Sector

No data is stored on the outside or inside tracks of the disk

The Hard Disc and Drive

• A hard disk is a circular metal disk coated with

magnetic material and usually sealed in a hard disk

drive inside the computer

• Some hard disk drives are not permanently fixed

inside the computer but are removable

• Data stored on a hard disk can be accessed much more quickly than data stored on a floppy disk

• Hard disks can store much more data than a floppy disk A typical hard disk inside a personal computer can hold many gigabytes of data

The Hard Disc and Drive

• Hard discs are normally built into the

computer.

• In a modern home PC the hard disc would

typically store 10Gb of data or more.

Non-magnetic storage

• Non-magnetic storage involves the use of

media not coated in magnetic material.

• Examples of this are: CD-ROM, Video

Disc, Digital Video Disc (DVD) and

• The size of memory, hard disc space, floppy drive space, programs, data files etc are all measured by the number of bytes, kilobytes, megabytes or

gigabytes (1024 megabytes) of data they

contain

445 floppy discs

=

1 CD-ROM

File compression

• File compression software can be used to make

files smaller so that more data can be stored in the same amount of space on backing store

• When a compressed file on backing store needs to

be used it must be decompressed.

• This can be done using decompression software

or by setting files up to be self-extracting which means that they can automatically decompress themselves

• Winzip is an example of software that can be used

to compress and decompress files.

Types of Access

• There are two types of access

• Random Access (also called Direct Access) devices retrieve the data you want straight away e.g CD-ROM drive, Hard disc drive, floppy disc drive

• Sequential (also called Serial) devices have to move through all the data, record after record, to find the data you need e.g Cassette tape, magnetic tape

Types of access

• Sequential Access

• To go from file A to file Z in a

sequential-access system, you

must pass through all intervening

files

• Sequential access is sometimes

called serial access.

• Random Access

• Refers to the ability to access data at

random In a random-access system,

you can jump directly to file Z

Types of Input

• Keyboard

Most keyboards are of the QWERTY type but not always They have always been used for inputting data to the computer

• Mouse

The mouse is very important in WIMP systems and is used to move a pointer around the screen and make selections by pressing a button

Advanced types of Input

• Trackball

A trackball is basically an upside down mouse

A trackball allows the user to move a small ball

in order to move the pointer across the screen.

• Graphics Tablet

A graphics tablet allows the user to draw on a special worktop As the user draws the details are stored on the computer system These devices are most often used by architects and designers.

The main use of a joystick is to play computer games by controlling the way that something moves on the screen

• Joysticks can be used to control

movement from side-to-side, down and diagonally

up-and-• A joystick will also always have at least

one button on it which can be used to make something happen like making a character in a game jump or a gun fire.

Touch Screen

A touch screen can detect exactly where,

on its surface it has been touched

Touch screens are used in a lot of fast food chains and

restaurants because they are easy to keep clean and re-program

if changes need to be made to the menu

• A digital camera takes pictures by converting the light passing

through the lens at the front into a digital

image

• A scanner can be used to input pictures and text into a computer

• There are two main types of scanner;

Hand-held and Flat-bed

• Voice Recognition

With voice recognition systems the computer can understand the words spoken to it and can carry out commands associated with the words Using voice recognition a letter can be dictated

instead of being typed at the keyboard.

• Handwriting Recognition

Handwriting can be recognised and the computer can convert the written text into typed text for storing.

Optical Character Recognition

• OCR

Is used to convert paper typed documents into

text files that can be edited and stored on a

computer system

OCR software can search a scanned image for

the shapes of letters, numbers etc When it

finds shapes that match it converts them to the

correct text and stores them in a file

Types of Output

• VDU or Monitor

Visual Display Unit (VDU) is

the proper name for the computer monitor The VDU allows us to see the output from the

computer.

• Plotter

A plotter is a device used for creating a hard copy of the output from a computer system Plotters use

special pens to draw the output as a series of lines

Plotters are often used to output building drawings and designs.

Monitor - Visual Display Unit

• The quality of the output on a monitor depends

on its resolution.

• The resolution of a monitor depends on the number of pixels that it can display

• A monitor or VDU is an

output device that can display

graphics and text and video

• The picture on a monitor is

made up of thousands of tiny

coloured dots called pixels.

More on Output Devices.

• There are three types of printers

Laser printers are expensive,

produce high quality printouts, can produce 8 to 12 pages in a minute

and are almost silent when they are working.

More on Output Devices

• Inkjet printers are cheaper than laser printers, they produce reasonable quality printouts (not quite as good as laser), can also printout in

colour , can print 2 to 5 pages in minute but there are a little noisy.

• Dot-matrix printers are the cheapest, they produce poor quality printouts, some can print

in colour, they struggle to print 1 page in a minute and they are VERY noisy.

More on Output Devices

• Voice Output

Voice output from a computer system is also known as speech synthesis Some voice output programs are know as text readers They take a text file and recite it

to the user

Other speech synthesis programs can tell the user what they are doing (for example floor

announcements in a speaking elevator).

Hello,

I am Hal!

Types of Media

• Media is the material used in devices.

• Examples of media are Floppy disc and CD-ROM.

• If CD-ROM is the MEDIA then the ROM drive is the DEVICE

• Multimedia systems combine graphics , text ,

sound , video and animation to provide a rich

experience for the user.

• Many interactive multimedia software titles are available now.

• Often these are stored on CD-ROM e.g Microsoft Encarta.

Virtual Reality

• Virtual Reality involves the user entering a 3D

world generated by the computer.

• To be immersed in a 3D VR world requires

special hardware e.g.

• A headset (containing goggles, headphones and a

position tracker )

• A data glove or data suit so that the users body can interact with the VR world.

 It consists of at least one input device, a processor and one output device.

is a computer system that is NOT

connected to other computers.

of parts that work together.

What is a Computer System ?

• A network is made up of two or more

computers linked together.

Advantages are:

Computer Networks

• A local area network is a computer network across one building or site.