// This illustrates how to read a file, stopping when an input failure occurs.
// It also illustrates how to do a few character-related tricks that are
// standard practice in C.
#include <stdio.h>
#include <ctype.h>
#define NUMLWRCASE 26

int main() {

   FILE* fp;
   // Try to open file named "RoughingIt.txt"; if this fails, fopen() will
   // return NULL, so we can check for a failure easily:
   if ( ( fp = fopen("RoughingIt.txt", "r") ) == NULL ) {
      printf("Error, could not open file data.txt\n");
      return 1;
   }
   char C;  // holds current character read from file
   
   int cCount[NUMLWRCASE] = {0};  // holds counter for each lower-case letter
   
   // fscanf() returns the number of values read; we can use that to detect
   // an input failure, whether it is at the end of the file or elsewhere:
   while ( fscanf(fp, "%c", &C) == 1 ) {
   
      // islower() returns true iff C is the ASCII code for a lower-case letter;
      // we typecast the parameter C because islower() expects an int, not a 
      // char to be passed to it
      if ( islower( (int) C) ) {
         // mild trick:  if C is a lower-case letter then C - 'a' equals the
         // sequence number for C ('a' is at 0, 'b' is at 1, ...)
         cCount[ C - 'a' ]++;
      }
   }
   
   // print out how many occurrences of each lower-case letter we found:
   for ( int i = 0; i < NUMLWRCASE; i++) {
   
      // mild trick:  'a' + i will be the ASCII code for the 
      // i-th lower-case letter; we typecast that to a char for
      // printing
      printf("%c:  %d\n", (char)('a'+i), cCount[i]);
   }
   
   return 0;
}