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---
# 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:  
  
```  
// while_statement.cpp  
  
#include <string.h>  
#include <stdio.h>  
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)