CXC Information Technology

Unit One – Basic Computer components

Basic computer components

Every computer, regardless of size, shape or function work in basically the same way

Input Process Output

Types of computers

Supercomputers Desktop Computers Notebook (laptop) Netbook Handhelds Tablet computers E-book Readers

Basic components CPU (Brain of the computer)

ALU – Arithmetic and Logic Unit Control Unit

Main memory RAM or ROM

Secondary memory (storage) Diskettes, CD-R’s etc.

Peripheral devices (input and output) Any external device attached

Information flow in a computer

INPUT

MAIN MEMORY

SECONDARY MEMORY

CPU:

ALU

Control unit

OUTPUT

KEYBOARDMOUSE

JOYSTICKWEBCAM

MICROPHONE

MONITORPROJECTORSPEAKERS

HEADPHONES

DISKETTECD

DVDFLASH DRIVE

Arithmetic and Logic Unit (ALU)

This is the part of the CPU which is responsible for all mathematical and logic functions. It carries out all calculations and makes any decisions which the computer needs.

Control Unit

This is the part of the CPU which is responsible for directing all instructions going to the CPU. It tells the instructions when and for how long they can have access to the CPU. The control unit is like a traffic warden, directing and controlling the flow of data.

Memory

A computer’s memory is either main (primary) or secondary (backing storage).

Main memory is where all the data needed by the CPU to carry out instructions is stored.

Secondary memory provides more space for storing data (diskettes, CD-Rs etc.)

Main memory

ROM (Read Only Memory)This memory can only be read from. It is non volatile (data remains even though

power is turned off) ROM contains the instructions needed for the

computer to “boot” up properly.

Main memory

RAM (Random Access Memory)This memory can be read from and written

to. It is volatile (when power is turned off, all

information is lost). Instructions needed by the CPU while it is

working are stored in RAM.The more RAM, the faster the processing

Main memory – Other types of ROM PROM (Programmable Read Only Memory)

This memory can only be reprogrammed ONCE. EPROM (Erasable Programmable Read Only

Memory) This memory can be reprogrammed more than once.

It must however be reset to its original state.

RAM vs. ROM

ROM works when the computer is booting up

RAM kicks in when the computer has started. The CPU uses RAM

Secondary storage is used to save data for later.

Units of memory

Bit – The smallest unit of storage in memory

Byte – a collection of bits (7 or 8) Kilobyte – 1024 bytes (210) Megabyte – 1024 kilobytes Gigabyte – 1024 megabytes

1 bit1 bit

8 bits = 1 byte8 bits = 1 byte