While vs. Do...While Loop: Understanding the Key Difference

While loops and do...while loops are both fundamental control flow structures in programming that allow you to repeatedly execute a block of code. However, they differ in how they determine when to execute the loop body.

• While loop: A while loop evaluates a condition first. If the condition is true, the loop body executes. After each execution, the condition is checked again. This process continues until the condition becomes false, at which point the loop terminates. This means a while loop might not execute even once if the initial condition is false.

• Do...while loop: In contrast, a do...while loop executes the loop body before checking the condition. It will always execute at least once, regardless of the initial condition. After the first execution, it then evaluates the condition. If true, the loop body executes again; if false, the loop terminates.

Therefore, the key distinction is the execution order: while loops are 'condition-first' while do...while loops are 'execute-first'. This implies that do...while loops are guaranteed to execute at least one iteration, while while loops may not execute at all if the initial condition is false.