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All data inside a computer is transmitted as a series of electrical signals that are either on or off. Therefore, in order for a computer to be able to process any kind of data, including text, images and sound, they must be converted into binary form. If the data is not converted into binary – a series of 1s and 0s – the computer will simply not understand it or be able to process it.

Representing text

When any key on a keyboard is pressed, it needs to be converted into a binary number so that it can be processed by the computer and the typed character can appear on the screen.

A code where each number represents a character can be used to convert text into binary. One code we can use for this is called ASCII. The ASCII code takes each character on the keyboard and assigns it a binary number. For example:

• the letter ‘a’ has the binary number 0110 0001 (this is the denary number 97)
• the letter ‘b’ has the binary number 0110 0010 (this is the denary number 98)
• the letter ‘c’ has the binary number 0110 0011 (this is the denary number 99)

Text characters start at denary number 0 in the ASCII code, but this covers special characters including punctuation, the return key and control characters as well as the number keys, capital letters and lower case letters.

ASCII code can only store 128 characters, which is enough for most words in English but not enough for other languages. If you want to use accents in European languages or larger alphabets such as Cyrillic (the Russian alphabet) and Chinese Mandarin then more characters are needed. Therefore another code, called Unicode, was created. This meant that computers could be used by people using different languages.