K&R(5.5): Character Pointers and Functions-strcmp

/* k&r(5.5): character pointers and functions
   created on Mar 21, 2011
   */
#include    "stdio.h"

int pstrcmp(char *, char *);

/* main: compares two character strings s and t, and return negative, zero or position if s t!
The value is obtained by substracting the characters at the first position where s and t disagree.
*/

int main()
{
    int i;
    char str1[] = "hello";
    char str2[] = "hello mark";

    i = pstrcmp(str1, str2);
    printf("%d\n", i);
}

/* strcmp: return <0 if s0 if s>t */
int astrcmp(char *s, char *t)
{
    int i;

    for (i = 0; s[i] == t[i]; i++)
      if (s[i] == '\0')
        return 0;
    return s[i] - t[i];
}

/* strcmp: pointer version */
int pstrcmp(char *s, char *t)
{
    for(; *s == *t; s++, t++)
      if (*s == '\0')//also *t=='\0'
        return 0;
    return *s - *t;
}