A-LevelComputer ScienceSystem software9618/31 · Oct/Nov 2021 · Q47 Marks
The following syntax diagrams for a particular programming language show the syntax of: • a digit • a capital letter • a character. [Figure 4.1]
- (a)Write the Backus-Naur Form (BNF) notation of the syntax diagram for character.[2]
- (b)(i)A password must begin with a character and be followed by one or more digits or capital letters. State an example of a valid password.[1]
- (b)(ii)A valid password is represented by the syntax diagram: [Figure 4.2] Write the BNF notation of the syntax diagram for password.[4]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.
- [2] One mark for each marking point (Max 2)
- • <character>::=
- • $ | % | & | * | #
- Complete answer
- <character>::= $ | % | & | * | #
- [1] For example: $A9E3
- [4] One mark for each marking point (Max 4)
- • <password>::=<character> ...
- • ... <code>
- • <code>::= ...
- • ... <digit>|<capital_letter>
- • ... |<digit><code>|<capital_letter><code>
- Complete answer
- <password>::=<character><code>
- <code>::=<digit>|<capital_letter>|<digit><code>|<capital_letter><code>
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