What is wrong with this C program to count the occurences of each vowel?

Question

PROBLEM:

Write a C program that prompts the user to enter a string of characters terminated by ENTER key (i.e. ‘\\n’) and then count the total number of the occurrence o

Answer 1

First of all you should put the return type for main: int ( ex: int main() ), this did not break your code but it the C standard and rises a warning from the compiler.

Chars in C take the numerical value from the ASCII encoding standard: http://upload.wikimedia.org/wikipedia/commons/1/1b/ASCII-Table-wide.svg, look at the values there ( 'a' is 97 for example), more on wikipedia : http://en.wikipedia.org/wiki/ASCII

All you do in your last for loop is compare the character to a,b,c,d,e.

What I would recommend you to do is make a switch for the character:

switch(c) {
    case 'a':
    case 'A':
        counter[0]++;
        break;
    case 'e':
    case 'E':
        counter[1]++;
        break;
    case 'i':
    case 'I':
        counter[2]++;
        break;
    case 'o':
    case 'O':
        counter[3]++;
        break;
    case 'u':
    case 'U':
        counter[4]++;
        break;
}

Alternatively, you could make five if statements.

It should work fine now.