I remembered my maths teacher having a T183 software that simulates the real calculator.

Does anybody whether it exist for free? Or must it be purchased?

 

There's a free TI-89 emulator available. I've tried it and it works "OK"

http://mathematics.mc.maricopa.edu/seims/TI-Emulator.htm

Other ones seem to require you to own the calculator.

http://www.ticalc.org/archives/files/fileinfo/84/8442.html