Programming concepts: FOR i ← 1 TO 5 … Instructions here … ENDFOR

The idea

This pseudocode shows a definite (count-controlled) FOR loop. The loop variable i is set to 1 at the start, and the body between FOR and ENDFOR runs once for each value from 1 to 5 inclusive, so the instructions execute five times. On each pass i takes the values 1, 2, 3, 4 and 5 in turn, and after the final pass the loop ends. The arrow ← means assignment, so i is assigned the starting value. Because the number of repetitions is fixed by the range 1 TO 5, this is definite iteration rather than a condition-controlled loop. A learner answering a multiple-choice question about this code should count the values in the range, identify the loop variable, and recognise that the body repeats a known number of times.

What earns the marks

• The construct is a definite (count-controlled) FOR loop because the start and end values are fixed.
• The loop variable i is assigned the value 1 at the start of the loop.
• The body executes five times, once for each of the values 1, 2, 3, 4 and 5.
• The loop ends after the pass in which i equals 5, because the range is inclusive.
• The arrow ← denotes assignment of the starting value to the loop variable.

Common mistakes and how to put them right

• Saying the body runs four times by subtracting the start from the end.

  Put it right by counting 1, 2, 3, 4, 5.

• Describing the loop as condition-controlled.

  Put it right by calling it definite (count-controlled) iteration.

• Believing i stays at 1 throughout.

  Put it right by listing its value at each iteration.

• Reading ← as 'equals' in a comparison sense.

  Put it right by describing it as assigning the start value.

Exam tips

• Count the values in the range explicitly to confirm the number of executions.
• Identify the loop variable and its start and end values before answering.
• Check whether the range is inclusive when deciding how many times the body runs.