A character set is a collection of characters that a computer can recognise from their binary representation.
When you press the keys on your keyboard, the keyboard sends binary information to the computer. How does the computer know what the binary information means?
A character set is a collection of characters that a computer can recognise from their binary representation.
Computers can therefore use this character set to convert between characters and binary numbers.
Modern computers use two main character sets: ASCII and Unicode.
The American Standard Code for Information Interchange (ASCII) is a character set which uses 7 bits to encode each character.
This means each character is assigned a binary number from 00000002 (010)
to 11111112 (12710),
and therefore ASCII can encode a total of 128 different characters.
Table 1 shows some ASCII characters and their encodings in binary, hexadecimal, and decimal.
Table 1
| CHAR | BIN | HEX | DEC |
|---|---|---|---|
| Space | 010 00002 |
2016 |
3210 |
| 0 | 011 00002 |
3016 |
4810 |
| 1 | 011 00012 |
3116 |
4910 |
| 9 | 011 10012 |
3916 |
5710 |
| A | 100 00012 |
4116 |
6510 |
| B | 100 00102 |
4216 |
6610 |
| Z | 101 10102 |
5A16 |
9010 |
| a | 110 00012 |
6116 |
9710 |
| b | 110 00102 |
6216 |
9810 |
| z | 111 10102 |
7A16 |
12210 |
Some things to note about ASCII:
•
The numbers (0 = 3016
to 9 = 3916),
uppercase letters (A = 4116
to Z = 5A16),
and lowercase letters (a = 6116
to z = 7A16)
are all in order
•
The characters before Space = 2016
are all control characters (like Null = 0016,
Backspace = 0816,
and Escape = 1B16)
•
There are no letters from other alphabets, because there was no room (7 bits only allows for 128 different characters)
Unicode is a different character set which uses multiple bytes for each character.
Unicode can therefore encode many more characters than ASCII can: it covers every major language in the world. It can even encode emojis 🤯!
The first 128 characters in Unicode are the same as ASCII. This means that if a character is in ASCII, it will have the same encoding in Unicode.
What is a disadvantage of using Unicode instead of ASCII?
Tap/click to reveal More storage will be required, as Unicode uses more bits per character than ASCII does.