Question

From this Web site
http://www.programmingsimplified.com/c-program-find-characters-frequency
They have an example that will count a – z but not A-Z or spaces or standard punctuations.

  while ( string[c] != '\0' )
  {
     /* Considering characters from 'a' to 'z' only */

     if ( string[c] >= 'a' && string[c] <= 'z' ) 
        count[string[c]-'a']++;

     c++;
  }

  for ( c = 0 ; c < 26 ; c++ )
  {
     if( count[c] != 0 )

Answer 1

To count all characters in the string use an int a[256] and use the characters of the string as indexes into the array and increment:

int counts[256] = { 0 }; /* Initialize all elements to zero. */

while (string[c]) counts[(unsigned char)string[c++]]++;