In this example, if...else statement is used to check whether an alphabet entered by the user is a vowel or a constant.
The five alphabets A, E, I, O and U are called vowels. All other alphabets except these 5 vowel letters are called consonants.
This program assumes that the user will always enter an alphabet character.
Example #1: Program to Check Vowel or consonant
#include <stdio.h>
int main()
{
char c
int isLowercaseVowel, isUppercaseVowel;
printf("Enter an alphabet: ");
scanf("%c",&c);
// evaluates to 1 (true) if c is a lowercase vowel
isLowercaseVowel = (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u');
// evaluates to 1 (true) if c is an uppercase vowel
isUppercaseVowel = (c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U');
// evaluates to 1 (true) if either isLowercaseVowel or isUppercaseVowel is true
if (isLowercaseVowel || isUppercaseVowel)
printf("%c is a vowel.",c);
else
printf("%c is a consonant.",c);
return 0;
}
Output
Enter an alphabet: G
G is a consonant.
The character entered by the user is stored in variable c.
The isLowerCaseVowel evaluates to 1 (true) if c is a lowercase vowel and 0 (false) for any other character. Similarly, isUpperCaseVowel evaluates to 1(true) if c is an uppercase vowel and 0 (false) for any other character.
If both isLowercaseVowel and isUppercaseVowel is equal to 0, the test expression evaluates to 0 (false) and the entered character is a consonant. However, if either isLowercaseVowel or isUppercaseVowel is 1 (true), the test expression evaluates to 1 (true) and the entered character is a vowel.
The program above assumes that the user always enters an alphabet. If the user enters any other character other than an alphabet, the program will not work as intended.
Example #2: Program to Check Vowel or consonant
The program below asks the user to enter a character until the user enters an alphabet. Then, the program checks whether it is a vowel or a consonant.
#include <stdio.h>
#include <ctype.h>
int main()
{
char c;
int isLowercaseVowel, isUppercaseVowel;
do {
printf("Enter an alphabet: ");
scanf(" %c", &c);
}
// isalpha() returns 0 if the passed character is not an alphabet
while (!isalpha(c));
// evaluates to 1 (true) if c is a lowercase vowel
isLowercaseVowel = (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u');
// evaluates to 1 (true) if c is an uppercase vowel
isUppercaseVowel = (c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U');
// evaluates to 1 (true) if either isLowercaseVowel or isUppercaseVowel is true
if (isLowercaseVowel || isUppercaseVowel)
printf("%c is a vowel.",c);
else
printf("%c is a consonant.",c);
return 0;
}