while

1. 문법

while (testExpression) 
{
    //codes 
}

2. 테스트 소스

#include <stdio.h>
int main()
{
    int number;
    long long factorial;

    printf("Enter an integer: ");
    scanf("%d",&number);

    factorial = 1;

    // loop terminates when number is less than or equal to 0
    while (number > 0)
    {
        factorial *= number;  // factorial = factorial*number;
        --number;
    }

    printf("Factorial= %lld", factorial);

    return 0;
}

3. 결과 

gcc -o while1 while1.c

hacker@HACKER:~/c$ ./while1
Enter an integer: 10
Factorial= 3628800