O-LevelComputer ScienceProgramming2210/21 · May/June 2020 · Q48 Marks
The pseudocode algorithm shown should allow numbers to be entered and should allow 50 numbers to be stored in an array. ``` Count ← 0 REPEAT INPUT Values [Count] Count← Count + 1 UNTIL Count = 0 ```
- (a)Explain why the algorithm will never end.[2]
- (b)Re-write the original pseudocode so that it terminates correctly and also prevents numbers below 100 from being stored in the array Values[ ][4]
- (c)Describe how you could change your pseudocode in part (b) so that it prevents numbers below 100 and above 200 from being stored in the array Values[ ][2]
Mark scheme
Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.
- [2] Any two correct statements (max two) e.g. The value of the variable Count begins as 0, and is incremented by 1 before it is tested by the loop condition, Count will never be 0 at the end of the loop
- [4] Count ← 0 REPEAT INPUT Number IF Number >= 100 THEN Values[Count] ← Number ENDIF Count ← Count + 1 UNTIL Count = 50
- One mark - separate INPUT statement
- One mark - IF statement attempted
- One mark - IF statement completely correct
- One mark - termination of loop updated
- [2] Any two correct statements (max two) e.g. Alter the IFstatement/add a second IF statement/comparison that's already there ..., so that additional criteria set an upper limit of <=200
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