iGCSE Computer Science - Distance Learning
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.
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
+ 1 = 65,356 characters!