// Demonstrating how to play with characters in C
// Program asks the user for a letter, checks if the letter is upper or lower
// case and then converts it to the opposite case

// Week 2, Lecture 3

// Problem: A user inputs a letter, we must check 
// if the letter is upper or lower case and then 
// output the same letter, but in the opposite case
// Possibilities/Breakpoints?
// 1. Scan in a letter (scanf())
// 2. Check if upper or lower case - if it is between a and z lower case; A and Z 
// then it must be upper case
// a <= character <= z
// character >= 'a' && character <= 'z'
// character >= 'A' && character <= 'Z'
// 3. If lower - then convert to an upper
// 4. If upper - then convert to a lower


#include <stdio.h>


int main(void){

    // Declare a variable of type char to scan in a letter into
    char character;
    // Initialise it by scanning into it
    printf("Enter a character: ");
    // Declare a variable that will store the output of scanf()
    int scanf_return;
    scanf_return = scanf(" %c", &character);

    if (scanf_return == 1){
        if (character >= 'a' && character <= 'z'){
            character = character - 'a' + 'A';
            printf("It is lower case, the new letter is: %c\n", character);
            // I need to convert it to an upper case
            // Let's say my input is 'a' = 97
            // that means I want it to become 'A' = 65 
        } else if (character >= 'A' && character <= 'Z') {
            character = character - 'A' + 'a';
            printf("It is upper case. the new character is %c\n", character);
        } else {
            printf("You did not enter a letter.");
        }
    }
    return 0;
}