That Blue Square Thing

Computer Science GCSE

Note: this page deals with the old Edexcel GCSE (grades A-G) which no longer exists. I'm keeping it as an archive and because a number of the resources will still apply to newer (grades 1-9) courses. The AQA GCSE CompSci pages deal with a current course.

Data Representation

Computers have to be able to reduce everything to binary values - 1s and 0s using binary numbers. This means that any item that needs to be stored by a computer - such as text, images and sounds - has to be able to represented using binary digits.

This content links to the binary section. In particular, the storage and transfer of files links very closely to the content about Bytes and bits. You'd be best off referring to that as you need to.

Text Encoding

Text encoding involves each character (each letter, punctuation marks etc...) being given a numerical code. This allows it to, eventually, be represented by binary numbers. By using a set of common codes data can be transfered from one computer system to another.

The two text encoding systems you need to know about are:

You need to make sure that you know how both of these systems work and their pros and cons.

PDF iconASCII code slides - a basic outline

PDF iconText encoding - detailed resource sheet with all the key information about ASCII and Unicode

PDF iconASCII code table - for reference

PDF iconComparing strings - why, when programming, "A" does not equal "a" (hint: it's all down to ASCII...)

There is a section of the BBC Bitesize site with notes about text encodingwiki link. It's in with a section about hexadecimal numbers.