added strcmp function & test

src/6_v_b_strcmp.c

@@ -0,0 +1,30 @@
+#include <stdio.h>
+
+char * cmp[] = {"before", "equal", "behind"};
+
+int strcmp(char * s1, char * s2) {
+
+	while (*s1 == *s2 && *s1) {
+		s1++;
+		s2++;
+	}
+
+	if (*s1 < *s2)
+		return -1;
+	if (*s1 > *s2)
+		return 1;
+	else
+		return 0;
+}
+
+int main(int argc, char * argv[]) {
+
+	char * s1 = "Aachen";
+	char * s2 = "Aach";
+	char * s3 = "Berlin";
+
+	printf("%s is %s %s\n", s1, cmp[strcmp(s1, s2)+1], s2);
+	printf("%s is %s %s\n", s1, cmp[strcmp(s1, s3)+1], s3);
+
+	return 0;
+}