Lesson 18: Looping Structures: The do-while Loop

The do-while loop is similar to while, but it guarantees that the loop body executes at least once, regardless of the initial condition.

do-while Loop Syntax

c do { // Code block to be executed } while (condition); // Note: Semicolon after the while condition is required!

How it Works (Exit-Controlled Loop)

1. The code inside the do block executes immediately.
2. After the first execution, the while (condition) is checked.
3. If the condition is True, the loop repeats; otherwise, it terminates.

Example: Menu Input Validation

A common use case is forcing user input until a valid choice is made.

c #include <stdio.h>

int main() { int choice;

do {
    printf("1. Start | 2. Options | 3. Exit\n");
    printf("Enter choice (1-3): ");
    scanf("%d", &choice);
} while (choice < 1 || choice > 3);

printf("Valid choice selected: %d\n", choice);
return 0;

}

Comparison: while vs. do-while