Which programming language to choose for teaching programming online?

Question

I would like to build a web service, which can be used for teaching programming and setting up programming quizzes.

I have envisioned that at its simplest form, the end user would see a web page which contains one to n questions, and as many text boxes for writing the code for each question. Right next to each text box there should be a "run" button, which would execute the program and print output of the program to the web page.

The language should be safe in the sense, that the code must be run in some kind of a sandbox. And naturally simple syntax would be a good thing.

I welcome different views on how you would implement such a service.

Answer 1

Javascript is a great language to teach programming; note that because execution happens in the user's own browser, there is little opportunity to do the hacking here (no code is sent up to the server).

Answer 2

There is http://codepad.org/ already, which can do same things.