a simple form of encryption could be to just NOT all of the characters in the message to encrypt them, and then just NOT them again to de-crypt them, you would write a program that does this. At first glance, the message will be gibberish, but the confusion will not last long, and for even the most amateur cracker, decoding the message wouldn't exactly be a difficult task...
Manipulating the bits that make up each character can change what they represent, i'm sure if you messed around a bit, you could do something relatively interesting, although i'm no expert, and i'm sure there are better solutions, but if you're just messing about, and want a basic level of encryption, don't be afraid to try something along those lines.
*what do I know about encryption?

*
---------------------------------------------------------------------------------------
I think I can program pretty well, it's my compiler that needs convincing!
---------------------------------------------------------------------------------------
And now a joke to lighten to mood :D
I wander what programming language anakin skywalker used to program C3-PO's AI back on tatooine? my guess is Jawa :P