Indicative content
How characters are mapped to codes
- Each character in a book title or author name is given a unique 7-bit binary code from the ASCII character set.
- The letter A, for example, is stored as the code 1000001 and the letter B as 1000010, so the catalogue can store letters as binary.
- Uppercase letters, lowercase letters, digits, punctuation and the space character each have their own ASCII code.
- The same character always uses the same code, so the text can be stored and read back correctly by the library system.
Why 7 bits are used for each character
- Seven bits give 2 to the power of 7, which is 128 different bit patterns, and this is enough to represent the letters, digits and punctuation needed in the catalogue.
- A standard keyboard has around 98 characters, so 6 bits would give only 64 codes and would not be enough.
- Using a fixed 7 bits per character means every character takes the same amount of storage, which makes the catalogue file simple to process.
Benefits of using ASCII for the catalogue
- ASCII is a standard character set, so the catalogue data can be exchanged between different computers and software.
- Author names and titles entered on one system will display correctly on another system that uses ASCII.
- ASCII uses only 7 bits per character, so the catalogue takes less storage than a character set that uses more bits.
- It is simple to encode and decode because each character has a single fixed code.
Levels
- Level 0 (0 marks): No rewardable content.
- Level 1 (1–2 marks): Basic, independent points are made, showing elements of understanding of key concepts/principles of computer science. (AO1) The discussion will contain basic information with little linkage between points made or application to the context. (AO2)
- Level 2 (3–4 marks): Demonstrates adequate understanding of key concepts/principles of computer science. (AO1) The discussion shows some linkages and lines of reasoning with some structure and application to the context. (AO2)
- Level 3 (5–6 marks): Demonstrates comprehensive understanding of key concepts/principles of computer science to support the discussion being presented. (AO1) The discussion is well developed, with sustained lines of reasoning that are coherent and logically structured, and which clearly apply to the context. (AO2)
Do not accept 8 bits or 256 characters as features of 7-bit ASCII; these are extended ASCII.