Example 1: From a C-style string

This program takes a C-style string from the user and calculates the number of vowels, consonants, digits and white-spaces.

#include <iostream>
using namespace std;

int main(){
    char line[150];
    int vowels, consonants, digits, spaces;

    vowels =  consonants = digits = spaces = 0;

    cout << "Enter a line of string: ";
    cin.getline(line, 150);
    for(int i = 0; line[i]!=''; ++i)
    {
        if(line[i]=='a' || line[i]=='e' || line[i]=='i' ||
           line[i]=='o' || line[i]=='u' || line[i]=='A' ||
           line[i]=='E' || line[i]=='I' || line[i]=='O' ||
           line[i]=='U')
        {
            ++vowels;
        }
        else if((line[i]>='a'&& line[i]<='z') || (line[i]>='A'&& line[i]<='Z'))
        {
            ++consonants;
        }
        else if(line[i]>='0' && line[i]<='9')
        {
            ++digits;
        }
        else if (line[i]==' ')
        {
            ++spaces;
        }
    }

    cout << "Vowels: " << vowels << endl;
    cout << "Consonants: " << consonants << endl;
    cout << "Digits: " << digits << endl;
    cout << "White spaces: " << spaces << endl;

    return 0;
}

Output

Enter a line of string: This is 1 hell of a book.
Vowels: 7
Consonants: 10
Digits: 1
White spaces: 6

Example 2: From a String Object

This program takes a string object from the user and calculates the number of vowels, consonants, digits and white-spaces.

#include <iostream>
using namespace std;

int main(){
    string line;
    int vowels, consonants, digits, spaces;

    vowels =  consonants = digits = spaces = 0;

    cout << "Enter a line of string: ";
    getline(cin, line);

    for(int i = 0; i < line.length(); ++i)
    {
        if(line[i]=='a' || line[i]=='e' || line[i]=='i' ||
           line[i]=='o' || line[i]=='u' || line[i]=='A' ||
           line[i]=='E' || line[i]=='I' || line[i]=='O' ||
           line[i]=='U')
        {
            ++vowels;
        }
        else if((line[i]>='a'&& line[i]<='z') || (line[i]>='A'&& line[i]<='Z'))
        {
            ++consonants;
        }
        else if(line[i]>='0' && line[i]<='9')
        {
            ++digits;
        }
        else if (line[i]==' ')
        {
            ++spaces;
        }
    }

    cout << "Vowels: " << vowels << endl;
    cout << "Consonants: " << consonants << endl;
    cout << "Digits: " << digits << endl;
    cout << "White spaces: " << spaces << endl;

    return 0;
}

Output

Enter a line of string: I have 2 C++ programming books.
Vowels: 8
Consonants: 14
Digits: 1
White spaces: 5