Due to the complexity of the GUI system, several pieces of RAM may be overwritten while it is running. They are:
- 73 bytes starting at AppBackupScreen (used for GUI rendering and mouse) (for future compatibility, it is recommended to leave the first 129 bytes of AppBackupScreen free, if possible)
- 4 bytes starting at iMathPtrs (used only in the GUI mouse)
- 4 bytes starting at iMathPtrs+5 (used only in FileOpen and FileSaveAs)
- RelocatablePtr and RelocatablePtr2 (used only in FileOpen, FileSave, and FileSaveAs)
In addition, you should be aware that Doors CS will change the size and contents of the ‘gui6’/‘gui7’ appvar during GUI execution. It will also change the contents, but not size of the DCS6/DCS7 appvar during GUI execution. It is not recommended that you use undeclared areas of the free user ram for storage while the GUI stack is open, as data corruption may occur. Declare any RAM you need as programs or appvars. Also remember to update pointers if your data file is in higher RAM than the gui6/gui7 appvar. In general, if you use the Associated Program (AP) system, Doors CS will handle keeping gui7 in higher memory than any AP file that is opened. Another important note is that the three GUI text input types, GUIRTextLineIn, GUIRPassIn, and GUIRTextMultiline all use an edit buffer, which temporarily consumes all of free RAM (but only when the user is actually typing in that text box). Therefore, be sure not to store any data in free RAM above in-RAM programs, which is already a bad idea to begin with.