iGCSE Computer Science - Distance Learning

Tutor Marked Assignment 6
Tutor Marked Assignment 8 (Programming)

Representing Digital Text (2023 Specification Only)

New 2023 Syllabus Only

We already know that computers hold data using binary, so representing characters requires the computer to convert from alphanumeric (letters & numbers as text) into binary.

GCSE computer science

So how do you convert a letter into binary? The simple answer is that you can’t. Instead, each character is assigned a number value which is stored in a table known as a Character Set.

There are two main character sets, both of which are discussed at GCSE. The first of these is ASCII (as-key), American Standard Code for Information Interchange.


If you haven’t completed the KS3 Computing course, now is a great time to watch the lesson on representing data. If you have completed the course, use this as a reminder!

One of the questions often asked in an exam is how many characters can ASCII represent. We can calculate this by knowing that it uses 7 bits of binary data to represent each character:

The maximum binary number with 7 bits is: 1111111

1111111 = 127

127 + 1 = 128

Why the +1? Because 0 is a number!

As digital representation gre, people wanted to be able to show a variety of languages in their documents which required different characters. Unforunately ASCII has a limitation on what it can represent with so few characters so an alternative had to be found. The Unicode character set was implemented with a much greater capacity, using 16 bits to represent each character.

With 16 bits, the capacity was enough to represent all possible alphabets and still have enough room to save emojis 🙂

16 bits = 1111 1111 1111 1111

or 65,535

+ 1 = 65,356 characters!