Hello guys! Im new in this forum and I hope to say for a long time since I'm new im programming right now.
Anyways, I have a big doubt on one assigment I have. I am not going to ask you to do it for me. What I want to know is what do I have to do?? The proffessor had explain me couple of times and I still dont get it! Im going to put the assigment below and if you guys understand what to do (it should be pretty easy since is the 1st assigment) please explain what do I have to do in simple words! (I dont want the code, just the explanation) Alright? Thankyou!

Write a decrypt/encrypt program.

Your program takes one argument on the command line, the key. It then uses that
key to encrypt/decrypt character-by-caracter what it gets on the standard input.
For every character from standard input it does and exclusive or with the next
character from the key. The result of the exclusive or is output on the standard
output. If all characters from the key have been used and there are more characters
inthe input, it starts over at the first character of the key. This process repeats until
all characters in the input have been modified in this way.

Hint: Be sure you use cin and cout in a raw mode where you get all the characters
that are being input.