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Home > Computing Studies > Computer systems > Low level machines

Computing Studies

Low level machines


The low level machine


Bits and Bytes

Computers can sense when a signal being sent is on or off. This is represented by a ‘1’ (on) or a ‘0’ (off). Each individual 1 or 0 is called a binary digit or bit and it is the smallest piece of data a computer system can work with.

Eight bits are grouped together to make one byte.

One byte provides enough codes (256) to represent all of the characters that appear on a standard keyboard. A byte is the basic unit used to measure computer memory size.

A table displaying the values of computer memory.


1 or 0


8 bits

Kilobyte (kB)

1024 bytes

Megabyte (MB)

1024 kilobytes

Gigabyte (GB)

1024 megabytes

Terabyte (TB)

1024 gigabytes

Input, Process, Output (IPO)

A program is a set of intructions which control the operation of the processor.

Programs often involve:

A block diagram showing how an electronic device can be thought of as three linked parts - input, process and output.

Input involves entering the data and instructions that the computer needs to carry out a particular task.

The process is what the computer is to do with the data or instructions that have been input.

Output is the set of results which is obtained when the instructions have been run.

The processor controls how all the other parts of the computer system work. It's the part of the computer which carries out calculations and which makes logic decisions. It is, in effect, the computer's brain.

Main memory

A running program is stored along with its data in the main memory of the computer.

Main memory is divided up into storage locations each with its own address.

A single storage location can hold one or more bytes of information.

Main memory size

This is the amount of memory allocated to a computer system. Most modern computers come with a minimum of 1 gigabyte of RAM.

Stored program

All programs and instructions that are stored in main memory are called stored programs.


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