Choose loops and validate input

Match the loop to the requirement

Use FOR for a known number of accepted items, WHILE when zero iterations are possible, and REPEAT when reading at least once is required. A sentinel marks the end of input; it is not ordinary data.

Separate attempts from accepted items

To read three valid scores: the outer loop counts accepted scores; the inner REPEAT handles attempts for one score. Add to Total only after validation succeeds.

DECLARE Score, Total, I : INTEGER
Total ← 0
FOR I ← 1 TO 3
    Score ← I * 2
    Total ← Total + Score
NEXT I
OUTPUT Total

This fixed-data version gives 12. Replacing the assignment with a validation loop should not change where the total is updated.

Read integers until one is 1 to 9 inclusive. Output only the accepted value.

DECLARE Code : INTEGER
// Must read at least once; stop only when valid

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Read N (1 to 5). For EACH score, read repeatedly until it is 0 to 20 inclusive. Output the total of the N accepted scores. Do not count invalid attempts.

// Plan, then write your solution

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Explain your reasoning

Explain your choice of data structure and loop. Identify one boundary case and predict its result. For a subroutine, explain what is returned or changed in the caller.

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