Iteration: FOR · ⁨反復：FOR⁩

FOR repeats a fixed number of times

• A FOR loop counts from a start value to an end value.
• NEXT marks the end of the loop body.

FOR I ← 1 TO 5
    OUTPUT I      // 1, 2, 3, 4, 5
NEXT I

A running total

• Start a total at 0, then add to it inside the loop.

Total ← 0
FOR I ← 1 TO 10
    Total ← Total + I
NEXT I
OUTPUT Total      // → 55

STEP changes the count

• STEP sets how much the counter changes each pass.
• STEP -1 counts down.

FOR I ← 5 TO 1 STEP -1
    OUTPUT I      // 5, 4, 3, 2, 1
NEXT I

Watch out

• Use FOR when you know how many times to repeat; use WHILE when you do not.
• The counter (I) and NEXT I must use the same name.

Common mistakes

• FOR I ← 1 TO N ... NEXT I runs n times, including both ends.
• The counter changes automatically each turn.

Now you try

• Use FOR ... NEXT. Type <- for ←.
• Press Check answer to test it.