count letters and words in string v1.c

/*
    count letters and words in string v1.c
*/

#include<stdio.h>

int main(void)
{
    int i = 0;                      // loops counter
    int countLetters = 0;           // counter for letters
    int countWords = 0;             // counter for words

    char str[] = "count how many words and letters there are";  // string to be analyzed

    while (str[i] != '\0')          // from beginning to end of string
    {
        if ( str[i] >= 'a' && str[i] <= 'z' || str[i] >= 'A' && str[i] <= 'Z' )
        {                           // if str[i] is letter, this is a new word and
            countWords++;           // increment countWords

            while(str[i] >= 'a' && str[i] <= 'z' || str[i] >= 'A' && str[i] <= 'Z' )
            {                       // then, while str[i] is letter
                countLetters++;     // increment countLetters
                i++;                // go to next character
            }
        }
        else                        // if str[i] is not letter
            i++;                    // go to next character
    }

    printf("\n %s \n",str);

    printf("\n countWords = %d \n",countWords);

    printf("\n countLetters = %d \n",countLetters);

    return 0;
}