Click here to download numlen.c.

/**********************************************
The function length(int n) is a recursive
function that returns the number of characters
needed to print out n.
 **********************************************/
#include <stdio.h>

int length(int);

int main() {
  // Get integer n
  int n;
  printf("Enter integer: ");
  fflush(stdout);
  scanf(" %i", &n);

  // Print out number of characters in n
  printf("Printing %i takes %i characters.\n", n, length(n));

  return 0;
}

int length(int n) {
  if (n < 0) {
    return 1 + length(-n);  // negatives!
  } else if (n < 10) {
    return 1;               // single digits! (base case)
  } else {
    return 1 + length(n/10);// multiple digit positive!
  }
}