[haha@Home testProg]$ cat 121.c
#include <stdio.h>
int main()
{
for (int i=0;i<9;i++)
printf("121");
////////////以上是程序
\\\\\\\\\\\\下面是编译
[haha@Home testProg]$ gcc 121.c
121.c: In function `main':
121.c:4: `for' loop initial declaration used outside C99 mode
121.c:6:2: warning: no newline at end of file