--- description: "Learn more about: while Statement (C++)" title: "while Statement (C++)" ms.date: "11/04/2016" f1_keywords: ["while_cpp"] helpviewer_keywords: ["while keyword [C++]", "while keyword [C++], syntax"] ms.assetid: 358dbe76-5e5e-4af5-b575-c2293c636899 --- # while Statement (C++) Executes *statement* repeatedly until *expression* evaluates to zero. ## Syntax ``` while ( expression ) statement ``` ## Remarks The test of *expression* takes place before each execution of the loop; therefore, a **`while`** loop executes zero or more times. *expression* must be of an integral type, a pointer type, or a class type with an unambiguous conversion to an integral or pointer type. A **`while`** loop can also terminate when a [break](../cpp/break-statement-cpp.md), [goto](../cpp/goto-statement-cpp.md), or [return](../cpp/return-statement-cpp.md) within the statement body is executed. Use [continue](../cpp/continue-statement-cpp.md) to terminate the current iteration without exiting the **`while`** loop. **`continue`** passes control to the next iteration of the **`while`** loop. The following code uses a **`while`** loop to trim trailing underscores from a string: ```cpp // while_statement.cpp #include #include char *trim( char *szSource ) { char *pszEOS = 0; // Set pointer to character before terminating NULL pszEOS = szSource + strlen( szSource ) - 1; // iterate backwards until non '_' is found while( (pszEOS >= szSource) && (*pszEOS == '_') ) *pszEOS-- = '\0'; return szSource; } int main() { char szbuf[] = "12345_____"; printf_s("\nBefore trim: %s", szbuf); printf_s("\nAfter trim: %s\n", trim(szbuf)); } ``` The termination condition is evaluated at the top of the loop. If there are no trailing underscores, the loop never executes. ## See also [Iteration Statements](../cpp/iteration-statements-cpp.md)
[Keywords](../cpp/keywords-cpp.md)
[do-while Statement (C++)](../cpp/do-while-statement-cpp.md)
[for Statement (C++)](../cpp/for-statement-cpp.md)
[Range-based for Statement (C++)](../cpp/range-based-for-statement-cpp.md)