Back to work on the TI-83 Plus port of BBC BASIC! To complement the graphics viewport I've added support for text viewports -- this lets you define the area the text console uses. The following VDU commands are now supported:

• VDU 24,;;;;
  Define a graphics viewport.
• VDU 28,,,,
  Define a text viewport.
• VDU 26
  Reset both viewports to their default settings (full screen).
• VDU 29,;;
  Defines the graphics origin.

The above screenshots defines the graphics viewport to fill the left hand side of the screen and shunts the text viewport over to the right half, using the following code:

VDU 24,0;0;47;63; VDU 28,12,0,23,9 VDU 29,24;32;

I've also added simple sprite drawing to BBC BASIC's PLOT command. PLOT usually takes a shape type and two coordinates, but for sprites (shapes 208..215) I've added an extra parameter - the address of the sprite data to use.



The above code allocates 8 bytes of memory (DIM ball 7) then copies the sprite data to it by use of the ? indirection operator. This is a little laborious, so in reality you'd probably store your sprites in a binary file external to the main program, and might load them like this:

(Note FN_loadSprite() at the end of the program). The result is the following:


Next up: drawing text at the graphics cursor position (as sprites).