Open Source Software

Suppose you were using a program you liked, and you found a bug in it, or thought of a useful feature to add to it.

If it's proprietary software, that made and sold by companies like Microsoft, you couldn't really do anything. Maybe write them an e-mail, but you couldn't really get anything done.

But if it were an open source program, you could download the source code (for free, the same way you got the program itself), modify it and then upload it so other can benefit from your work.

Open source software also promotes good programming technique. If you know no one else is going to look at your code, you might just not bother making it readable, making it hard to change in the future. But if you're releasing it to an open source project, people will complain and be less likely to use your code if it is unreadable.