strcmp.c

int strcmp(const char* s1, const char* s2)
{
    while(1)
    {
        if(*s1>*s2)
        {
            return 1;
        }else if(*s1<*s2)
        {
            return -1;
        }else if(*s1=='\0')
        {
            return 0;
        }
        s1++;
        s2++;
    }
}