Pointer Math Example

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

int main(void)
{
        // these are the letters we are going to change to uppercase
        char    vowels[] = {'a', 'e', 'i', 'o', 'u'};

        // this is the string we are going to perform the operation on
        char    *str = "Hello World";

        // iterator for the inner for-loop
        int     i;

        // while we haven't reached the null terminator
        for (; *str != '\0'; str++)
        {
                // storing the current character we're checking
                char    current_char = *str;

                // looping through to see if the character is a lowercase vowel
                for (i = 0; i < 5; i++)
                {
                        char    current_vowel = vowels[i];

                        // if it is, make it upper case
                        if (current_char == current_vowel)
                        {
                                // 32 is the delta between 'a' and 'A' or 97-65
                                current_char -= 32;
                        }
                }

                printf("%c", current_char);
        }

        printf("\n");
        return 0;

}