The only exceptions are the loops whereĮxpression is a constant expression do while(true) is always an endless loop.Īs with all other selection and iteration statements, the do-while statement establishes block scope: any identifier introduced in the expression goes out of scope after the statement.īoolean and pointer expressions are often used as loop controlling expressions. This allows the compilers to optimize out all unobservable loops without proving that they terminate. If the execution of the loop needs to be continued at the end of the loop body, continue statement can be used as a shortcut.Ī program with an endless loop has undefined behavior if the loop has no observable behavior (I/O, volatile accesses, atomic or synchronization operation) in any part of its statement or expression. If the execution of the loop needs to be terminated at some point, break statement can be used as terminating statement. If the controlling expression needs to be evaluated before the loop body, the while loop or the for loop may be used. The evaluation of expression takes place after each execution of statement (whether entered normally or by a goto).

The repetition occurs regardless of whether the loop body is entered normally or by a goto into the middle of statement.

(C23)optional list of attributes, applied to the loop statementĪ do-while statement causes the statement (also called the loop body) to be executed repeatedly until the expression (also called controlling expression) compares equal to 0. This expression is evaluated after each iteration, and if it compares equal to zero, the loop is exited.Īny statement, typically a compound statement, which is the body of the loop Attr-spec-seq (optional) do statement while ( expression ) Īny expression of scalar type.

Example programs in c using do while