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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