After spending a few days fixing bugs/issues, we can now successfully start up Microsoft BASIC 2.10, and run BASIC sample code applications with it. It looks a bunch of stuff is now working:

• The BASIC sample apps seem to all be opening up and running the basic code is working fine in the BASIC interpreter.
• Sample code listing, formatting and scrolling (by dragging text selection with mouse) appears to be working.
• Trace and single-stepping seem to work ok using “Run” menu (and stopping using cmd+period).
• The BASIC sample apps seem to be able to draw text and pictures, read files, and create menus, windows and dialogs.

There’s still a few issues to iron out though:

• Only binary version of MS BASIC works, decimal version has some issues.
• Standard File Package is still unfinished, so opening BASIC applications for testing is done temporarily using hard-coded SFReply records.
• TextEdit input does not work yet properly, so for now we can only run existing sample apps. Interestingly, MS BASIC uses custom text input field which appears to do all the text drawing/selection itself without TextEdit, but depends on it for text input. This also prevents “Command” window from being much of use.
• SOUND command does not appear to work yet, and there’s no visible signs of attempted calls to .Sound driver or sound hardware, so it needs further investigation. This may be related to sound missing from a few other test applications.