Chapter 12: Loop Constructs

Definition: A statement or set of statements executed repeatedly is known as a loop. Also called iterative or repetitive structure.

• Counter-Controlled Loop: Number of iterations is known in advance. Uses a counter variable (e.g., for loop).
• Sentinel-Controlled Loop: Number of iterations is unknown. Terminates when a special value (sentinel) is encountered (e.g., while loop reading input until -1).

Definition: Simplest loop. Executes executed one or more statements while the given condition remains true. Useful when iterations are unknown.

Syntax: while (condition) { statement(s); }

Condition is checked before execution. If false initially, loop never executes.

Definition: Executes statements while a condition is true, but checks the condition after the body.

Syntax: do { statement(s); } while (condition);

Key Feature: Guaranteed to execute at least once, even if the condition is false initially.

Definition: Most flexible loop, normally used when iterations are known (Counter-Controlled).

Syntax: for (initialization; condition; increment/decrement) { statement(s); }

• Initialization: Sets starting value (executed once).
• Condition: Checked before each iteration.
• Increment/Decrement: Updates counter after each iteration.

Definition: A loop inside another loop. The inner loop completes all its iterations for each single iteration of the outer loop.

Example: Clock logic (inner loop for seconds, outer loop for minutes).

• break: Immediately exits the loop. Control moves to the statement following the loop.
• continue: Skips the remaining statements in the current iteration and moves to the start of the next iteration.
• goto: Translers control unconditionally to a labeled statement. Use is generally discouraged as it makes code hard to follow.