so i made;
char[] key = new char[7];
And then i assigned a number to each of it. (the most right ones are the ones i assigned)
but what does the numbers in the middle mean exactly? what can we do with them? are they useful?
They're the ASCII codes for each of those characters. So, when you assign '7', for example, that's really just shorthand for assigning 55 which is what represents the '7' character.
They are indeed very useful. For example, if you wanted to determine if a given character is a capital letter, you can just check if it's ASCII code is between 65 (i.e. 'A') and 90 (i.e. 'Z'). You can also shift characters around by performing arithmetic on the values, among other things.
