+ return *s2 - *s1;
+}
+
+int strncmp(const char *s1, const char *s2, int n)
+{
+ int i = 0;
+
+ while (i < n && s1[i] && s2[i] && s1[i] == s2[i])
+ i++;
+
+ if (i == n)
+ return 0;
+
+ return *s2 - *s1;
+}
+
+char *strchr(const char *s, int c)
+{
+ while (*s && *s != c)
+ s++;
+
+ if (*s == c)
+ return (char *)s;
+
+ return NULL;