原型：extern int strcmp(char *s1,char * s2，int n);
        
  用法：#include <string.h>
  
  功能：比较字符串s1和s2的前n个字符。
  
  说明：
        当s1<s2时，返回值<0
        当s1=s2时，返回值=0
        当s1>s2时，返回值>0
  
  举例：

      // strncmp.c
      
      #include <syslib.h>
      #include <string.h>

      main()
      {
        char *s1="Hello, Programmers!";
        char *s2="Hello, programmers!";
        int r;
        
        clrscr();
        
        r=strncmp(s1,s2,6);
        if(!r)
          printf("s1 and s2 are identical");
        else
        if(r<0)
          printf("s1 less than s2");
        else
          printf("s1 greater than s2");
        
        getchar();
        clrscr();
        
        r=strncmp(s1,s2,10);
        if(!r)
          printf("s1 and s2 are identical");
        else
        if(r<0)
          printf("s1 less than s2");
        else
          printf("s1 greater than s2");

        getchar();
        return 0;
      }
      
  相关函数：bcmp,memcmp,stricmp,strnicmp