How to test a code online? [closed]

Question

I am preparing for technical interview and would like to brush my coding skills. I have written a C++ program and would like to test it online. I don't have access to any linux compiler on my machine. Where can I do it? I have perception that I can do it in code.google.com -> Google Code Playground

but I don't see where I can choose my compiler.

I have written a simple C hello world program in "edit code" panel and have clicked on "Run code" but it has been a while and nothing appears in bottom output window.

Please help. Thanks,