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# C Do-While Loop
A `do-while` loop is a post-test iteration control structure in C that guarantees the execution of its statement block at least once. Unlike pre-test loops (such as `while` or `for`), the `do-while` loop evaluates its controlling expression at the bottom of the loop, strictly after the loop body has executed.
## Syntax
```c theme={"dark"}
do {
// Loop body: statements to execute
} while (expression);
```
## Execution Mechanics
1. **Unconditional First Pass:** Control flow enters the `do` block and executes the enclosed statements without any prior condition checks.
2. **Expression Evaluation:** After the loop body completes, the scalar `expression` within the `while` clause is evaluated.
3. **Branching:**
* If the expression evaluates to a **non-zero value (true)**, control flow jumps back to the top of the `do` block, initiating the next iteration.
* If the expression evaluates to **zero (false)**, the loop terminates, and control flow passes to the next sequential statement in the program.
## Technical Characteristics
* **Terminating Semicolon:** The `do-while` construct strictly requires a semicolon `;` immediately following the `while (expression)` clause. Omitting this is a common syntax error that will halt compilation.
* **Scope:** Variables declared inside the `do` block have block scope and are destroyed at the end of each iteration. They cannot be referenced in the `while` expression, as the expression sits outside the lexical scope of the loop body.
* **Control Flow Interruption:**
* A `break` statement inside the body immediately terminates the loop, bypassing the `while` evaluation.
* A `continue` statement inside the body skips the remaining statements in the current iteration and jumps directly to the `while (expression)` evaluation to determine if the loop should proceed.
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