While

Definition

Condition-controlled loop that tests its expression at the start of the block.

Advantages

Highly secure because if the entry condition is false, the loop code is safely skipped entirely.

Disadvantages

If the entry condition is never met, the code inside runs zero times, which can cause downstream variable initialization bugs.

Key Phrase

Repeat checks at the exit door; While checks at the entrance

Exam Question

Analyze the given pseudocode segment. Identify why the programmer selected a REPEAT...UNTIL loop structure instead of a WHILE loop for a user password validation entry.