| Bits and Bytes | ||
| The size of a computer's memory is measured by the amount
of data which can be stored in it. This is measured in bytes.
|
||
|
|
||
| Data is stored in memory as a number of 0s and 1s. Each of
these is called a bit (Binary
digIT), so for example the number 0110
is a 4-bit binary number.
8 bits is called 1 byte.
|
The reason
that binary numbers are used is that memory consists of millions of
two-state devices (think of them as switches).
Each of these can only be in one state (0) or the other (1). |
|
| Using the ASCII system
of coding each character is stored as a
unique 8-bit pattern. (A is 01000001; B is
01000010 etc..)....
1 byte of storage is needed to store one character, so to store the word ‘FRED’ would need 4 bytes of storage.
|
ASCII stands for American Standard Code for Information Interchange...Most computers use the same system so data can be transferred from one computer to another. | |
| A Kilobyte is 1024
bytes. A Kilobyte is usually abbreviated to K, and you will sometimes
see a computer described as having 640K RAM. This means that there are
640 kilobytes of memory in the computer.
A Megabyte (abbreviated to Mb) is 1024 kilobytes, so 1 Mb = 1024 x 1024 bytes = 1048576 bytes (approx 1 million) A Gigabyte (abbreviated to Gb) is 1024 Mb so 1 Gb = 1024 x 1048576 = 1073741824 bytes (approx 1 billion)
|
You can think of data
stored in memory or on disc as looking like..
1011001011001010 |
|
| Exercise : Bits and Bytes | ||
| The number 100111 has
bits. There are
bits in 1 byte.
The word "HEDGEHOG" would need bytes of memory to store it and each character has its own unique 8-bit ASCII code. 1 Kilobyte (K) = bytes. 1 Megabyte (Mb) = kilobytes. 1 Gigabyte (Gb) = megabytes.
|
||
| (Green indicates success) | ||
 |
||
