Count Letters, Digits, Vowels, Spaces and Symbols in C

Algorithm

1. Read a line with fgets, which keeps spaces, unlike scanf with %s.
2. Remove the trailing newline that fgets stores.
3. For each character: a letter counts as an alphabet and as a vowel or consonant; a digit counts as a digit; a space counts as a space; anything else counts as a special character.
4. Print all the counts.

C program

#include <stdio.h>
#include <string.h>
#include <ctype.h>

int main(void) {
    char line[200];
    int i, letters = 0, digits = 0, vowels = 0, consonants = 0, spaces = 0, special = 0;
    char ch;

    printf("Enter a line of text:\n");
    if (fgets(line, sizeof line, stdin) == NULL) {
        printf("Error: no input\n");
        return 1;
    }
    line[strcspn(line, "\n")] = '\0';

    for (i = 0; line[i] != '\0'; i++) {
        ch = (char)tolower((unsigned char)line[i]);
        if (isalpha((unsigned char)ch)) {
            letters++;
            if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
                vowels++;
            } else {
                consonants++;
            }
        } else if (isdigit((unsigned char)ch)) {
            digits++;
        } else if (ch == ' ') {
            spaces++;
        } else {
            special++;
        }
    }

    printf("Alphabets  : %d\n", letters);
    printf("Vowels     : %d\n", vowels);
    printf("Consonants : %d\n", consonants);
    printf("Digits     : %d\n", digits);
    printf("Spaces     : %d\n", spaces);
    printf("Special    : %d\n", special);
    return 0;
}

Sample input and output

Hello World 2024!

Enter a line of text:
Alphabets  : 10
Vowels     : 3
Consonants : 7
Digits     : 4
Spaces     : 2
Special    : 1

(no input)

Enter a line of text:
Alphabets  : 0
Vowels     : 0
Consonants : 0
Digits     : 0
Spaces     : 0
Special    : 0

How the program works

fgets reads the whole line including spaces, which scanf with %s would stop at. strcspn finds the first newline so it can be replaced with the string terminator.

The character is converted to lower case before the vowel test so that capital letters such as E are counted as vowels too. ctype functions take an unsigned char value to stay safe with non-ASCII bytes.

Viva questions

Common mistakes

• Using scanf("%s") and missing everything after the first space.
• Counting the newline left by fgets as a special character.