A simple model of the computer

MainMemory

OutputDevices

InputDevices

BackingStorage

The ProcessorArithmetic and Logic Unit (ALU)

Carries out calculations e.g.

10110011+ 11110010

ALU

The Processor

ALUControl

Unit

Control Unit

Decodes and executes instructions

Manages flow of information around CPU

The Processor

ALUControl

Unit

Register

Registers

Small number of very fast temporary storage locations which hold data

Register

Register

Register

The Processor and MemoryA processor looks like this

The Processor and MemoryA processor looks like this

and memory (RAM) looks like this

The Processor and Memory

Processor speed is measured in Megahertz (MHz)

A typical processor will have a speed of between 2 and 3.6 MHz BUT some computers have more than one processor

The Processor and Memory

Processor speed is measured in Megahertz (MHz)

A typical processor will have a speed of between 2 and 3.6 MHz BUT some computers have more than one processor

RAM is measured in Gigabytes (GB)

A typical computer will come with between 2GB and 8GB of RAM

Memory (RAM)

Main Memory

Address

10987654321

Large number of storage locations which hold data and programs

Each location has it’s own unique address

1111001100011010101011010011001111100000

Memory (RAM)

Main Memory

Address

10987654321

Known as RAM (Random Access Memory)

When the computer is switched off, RAM is cleared

Processor and memory

MainMemory

Which is why we need...

Processor, memory and backing storage

MainMemory

BackingStorage

Backing StorageThe most common form of backing storage is a hard disk drive which looks like this

Backing Storage

The circular area of a hard disk (the platter) is made of magnetic material

The storage space of a hard disk is measured in Gigabytes (GB)

A typical computer system will come with 250GB – 1000GB of storage space

Backing Storage

What other backing storage devices can you think of?

Backing Storage

What other backing storage devices can you think of?

Optical devices (CD-ROM / DVD-ROM)

Memory cards

USB Flash memory

ROM

We have seen that the computer’s memory is known as RAM which stands for:

RandomAccessMemory

RAM is cleared when the computer is switched off.

ROM

The computer also has special memory called ROM. This stands for:

ReadOnlyMemory

ROM does not get cleared when the computer is switched off

ROM contains the programs which tell the computer what to do when it is switched on

CreditsS2-3 Curriculum for Excellence – Inside the Computer

M. Cunningham, Forrester High School (2011)

All images licenced under Creative Commons 3.0• Intel Insides by Ryan Maclean (rcmaclean on Flickr)• Hard Disk by Jeff Kubina