What is a 'Hacker'

I mean from a writer's perspective. If you had a character who was a hacker (or a cracker), how would you make him convincing. To be  believable, you have to enter their mindset. Here are some ideas I've gotten from my computer friends, my fellow WordDreams blogger, and The New Hacker's Dictionary:

They want to write their native language well. Though it's a common stereotype that programmers can't write, a surprising number of hackers are very able writers.They read science fiction and go to sci