hardware - bh

8/13/2019 Hardware - BH

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GCSE Information Technology

Computer Systems

Computer System involves 3 stages

Input, Process, Output

Also a need to store data

Backing StorageDevices

InputDevices

Central ProcessingUnit (CPU)

OutputDevices


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Hardware and SoftwareComputer programs that tell (instruct)

the hardware how to work.

Files:Anything that can be stored is

also called software. Saving a word-

processed letter, or a spreadsheet, as a

computer file.


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Hardware- any part of acomputer that you can touch.

Hardware

The basic hardware of any computer consists of: central processing unit (CPU)

memory,

input, outputand backing storagedevices.

An individual piece ofhardware is called a device.


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Components (1)

Motherboard.CPU/Processor.

Memory/RAM.

Video Card/Graphics Adapter.Sound Card.

Modem.

Hard DrivePorts.


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The central processing unit (CPU)

where the searching and sortingof data, calculating and decision-

making goes on.

The CPU contains the

Cache Memory Control Unit Arithmetic and Logic Unit (ALU).

The Control Unitfetches instructionsfrom the main

memory, decodes themand causes them to beexecuted by the ALU.

TheALUperforms calculationsand makes decisionsusing these instructions.


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CPU


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Random Access Memory (RAM)

RAM is the computers

working memory.

RAM temporarilystoresprograms and datathat are

being used

The contents of RAM can be changed and are lostwhen the computer is turned off.

Memory which is wiped clean when the computeris turned off is called volatile memory.


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RAM Memory


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Read Only Memory (ROM)

ROM memory chips stores the program that runswhen the computer is turned on which loads theoperating system (e.g. Windows) from disk.

The contents of ROM cant be changedand arenot lostwhen the computer is switched off.

Memory which isn't wiped clean when thecomputer is turned off is called non-volatilememory.


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BITS and BYTES

Computers store and process data. These areelectronic charges represented by binarynumbers.

A single unit in binary is a bit which stands for

binarydigit.Computer memory is measured in bytes.One byte is made up of eight bits.One byte can store one character.

0 1 0 0 0 0 0 1

The eight bit binary code in thisbyte represents the letterA


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The size of a computersmemory is normally

measured in kilobytes (Kb), megabytes(Mb) or gigabytes (Gb). The table belowshows some of the main units of size that weuse to measure computer memory.

Measurement Size (bytes) Symbol

kilobyte 1,024 Kb

megabyte 1,048,576 Mb

gigabyte 1,073,741,824 Gb

BITS and BYTES (cont.)


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Switches and binaryComputers only understand switches being turned on

and off

these become signalsProgrammers interpret each combination of signals todo different things (e.g. to put things on the screen)

How powerful a computer is depends on how many

different signals it can receive.8 bit computers could receive 255 signals

Each time a switch is added, the number of signalsdoubles

Signals are added in multiples of 8

1 0 0 0 0 0 1 0

255 8 bit

1 0 0 0 0 0 1 0

16,000,00024 bit

1 0 0 0 0 0 1 0

65,00016 bit

1 0 0 0 0 0 1 0

4,000,000,000,000

32 bit

?

1 0 0 0 0 0 1 01 0 0 0 0 0 1 0 1 0 0 0 0 0 1 0 1 0 0 0 0 0 1 0

64 bit


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Mobile Computing

Laptops/Notebooks

Palmtops

PDAs


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Microcomputers

Microcomputers are sometimes called PCs, or

personal computers or desktops.

A typical PC system consists of:

A base, or tower unit that contains a CPUand

backing storage devices, normally a CD/DVD drive,and a hard disk drive.

Input devices, normally a mouse and keyboard.

Output devices, typically a screen, printer andspeakers.


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