I use the function printf, the program compiles and run, but when I go to the Output Window I don't see a thing
Oh boy... We're going to need a lot more information to answer that question...
Your best bet is to "zip" your program files and attach them to a message...
In POIDE open your project and select Project -> Zip Project Files...
In the forum click reply write a description of what you are trying to do...Is it a windows program, etc.
Then click Attachments and other options and attach your project ZIP file to the message.
I (and probably a few others) will look at your project and try to give you some help with it....