The TI-89 graphing calculator can store variables, settings and flash applications among other things in its internal memory. This memory can be cleared if you need more space or to stop unused programs you create from building up and becoming unmanageable.
Press the blue "2ND" key, then the "6" key.
When the memory screen appears, press F1.
Decide which kind of memory you wish to delete. Generally, clearing RAM clears all user-defined variables, and programs or folders you have made, and resets all system modes (like degrees/radians) to factory settings. Clearing flash ROM clears flash applications. There is also an option to clear both kinds of memory.
Select the memory you wish to clear and press "ENTER."