C Program To Count Frequency Of Vowels

The C program to count the frequency of vowels, consonants and white spaces for a given word or a sentence is a string manipulation program. A C loop with conditions that checks the given input string and count the number of vowels, consonants, and white spaces.


We compiled this program using Dev-C++ compiler installed on a Windows 7 64-bit system. You may try another standard C compiler and to get an error free program make necessary changes to the source code.

Also, before you try this example, learn following C programming concepts. If you are familiar with them, continue reading.

Problem Definition

In C language every string is like an array with each character of the string hold a position in this array. The last character is null character by default.

Using this array logic, the program read a word or a sentence during execution and check each and every character of input string. It counts the number of vowels, consonants and white spaces.


For example, the array representation of word – SPIDERMAN as follows.

\begin{aligned} &0 \hspace{5px}1  \hspace{5px}2\hspace{5px} 3 \hspace{5px}4 \hspace{5px}5 \hspace{5px}6\hspace{5px} 7\hspace{5px} 8 \hspace{5px}9 \\ 
&S \hspace{3px} P\hspace{3px} I \hspace{3px}D \hspace{3px}E \hspace{3px}R \hspace{3px}M\hspace{3px} A \hspace{3px}N \hspace{3px}\backslash\empty\end{aligned}

Note:- The Null character is added to all the strings in C by default.

Flowchart – Program to Count Frequency of Vowels

Flowchart – C Program to count the frequency of Vowels.

Program Code – Program to Count Frequency of Vowels

/*Read a sentence and print frequency of each vowels and the total count of consonants */
#include <stdio.h>
#include <conio.h>
int main()
    char str[100];
    int a,e,i,o,u,consonant,whitespace;
    a = e = i = o = u = consonant = whitespace = 0;
    int k;
    /* Get the Sentence */
    /* read the sentence */
        if(str[k]== 'a') 
            a = a+1; 
        else if(str[k] == 'e') 
            e = e +1; 
        else if(str[k] == 'i') 
            i = i +1; 
        else if( str[k] == 'o') 
            o = o + 1; 
        else if(str[k] == 'u') 
            u = u+1; 
         else if((str[k] >= 'a' && str[k] <= 'z')||(str[k] >= 'A' && str[k] <= 'Z'))
            consonant ++;
        else if (str[k] == ' ')
    printf("a :%d\n",a);
    printf("e :%d\n",e);
    printf("i :%d\n",i);
    printf("o :%d\n",o);
    printf("u :%d\n",u);
    printf("Consonant :%d\n",consonant);
    printf("whitespace :%d\n",whitespace);
    /* count vowels and consonants */
    /* print the results */
    return 0;

Apart from being a string program, we used built-in functions from C standard library to get string input (gets) and compute the length of the given input string (strlen).


The output of the program is given below. When the sentence ” A large reptile” is entered, the program reads all the vowels, consonants and white spaces and print the results.

A large reptile
a :1
e :3
i :1
o :0
u :0


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