C :: Counting Function - Prints All Input Lines That Are Longer Than 80 Characters

I'm doing an exercise that prints all input lines that are longer than 80 characters. I rather not use any libraries so I decided to write my own function that counts characters to use it in my main program. However when integrate things my function returns zero all the time.

Here is my full code:

/* Exercise 1-17 Write a program to print all input lines that are longer than 80 characters */

#include<stdio.h>
/* Declarations*/
#define MAX_STRING_LEN 1000
int count_characters(char S1[]);
int main() {

[Code] .....

So I was trying to debug my count_characters() function and this is the code if I was to run it seperately:

Code:
#include <stdio.h>
/* counts character of a string*/
main() {
int nc = 0;
int c;
for (nc = 0; (c = getchar()) != '
'; ++nc);
printf("Number of characters = %d
", nc);
}

which works...