C练习--大小写转换(用到函数\数组\指针)

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#include <stdio.h>
#define PASS "FISHC"
#define MAX 40
void abc(char * cyp);
int main()
{
char cyp[100];
printf("密码校验:\n");
gets(cyp);
abc(cyp);
while (strcmp(cyp,PASS) != 0)
{
  puts("密码错误!");
  gets(cyp);
  abc(cyp);
}
puts("密码正确!\n");

return 0;
}
void abc(char * cyp)
{
int i,len;

len = strlen(cyp);
for (i = 0; i<= len; i++)
  if (cyp[i]>='a' && cyp[i]<= 'z')
   cyp[i]-=32;
}