a2d/desktop

DeskTop diassembly notes

DESKTOP.SYSTEM

A short (8k) loader program. This is likely responsible for copying the rest to a RAM card (if available), then invoking the main app.

DESKTOP2.$F1

This is large - 111k. It includes a loader, the DeskTop app (with both main memory and aux memory segments, filling everything from $4000 to $FFFF (except for I/O space and ProDOS), and still having more code - probably the disk copy code which is swapped in dynamically.

The file is broken down into multiple segments:

• segment 0: load - offset $0000, length $0580, loaded at $2000
• segment 1: aux1 - offset $0580, length $8000, loaded at $4000 (through $BFFF)
• segment 2: aux2 - offset $8580, length $1D00, loaded at $D000 (through $ECFF)
• segment 3: aux2 - offset $A280, length $0500, loaded at $FB00 (through $FFFF)
• segment 4: main - offset $A780, length $7F00, loaded at $4000 (through $BEFF)
  • main $BF00-$BFFF is ProDOS buffers
  • main $C000-$CFFF is I/O space
  • main $D000-$FFFF is ProDOS
• segment 5: TBD - 38k so must be further subdivided. Disk Copy???

Structure

Loader

loader.s

Invoked at $2000; patches the ProDOS QUIT routine (at LC2 $D100) then invokes it. That gets copied to $1000-$11FF and run by ProDOS.

The invoked code stashes the current prefix and re-patches ProDOS. It then (in a convoluted way) loads in the second $200 bytes of the system file at $2000 and invokes that.

GUI Library "A2D"

a2d.s

AUX $4000-$8DFF is the GUI library used for the DeskTop application and (presumably) for disk copy and Selector apps (TBD).

Entry point is $4000 with a ProDOS MLI-style calling convention

• Font is at $8800

• Part of $8500-$87FF looks like part of "DeskTop" (see below), dealing with online volumes.

"DeskTop" Application

desktop.s

DeskTop application code is in the lower 48k of both Aux and Main:

• Aux $8E00-$BFFF - sitting above the GUI library
• Main $4000-$BEFF

...and in the Aux language card area (accessible from both aux and main code) are relays, buffers and resources:

• Aux $D000-$ECFF - relays and other aux/main helpers, resources (menus, strings, window)
• Aux $ED00-$FAFF - hole for data buffer
• Aux $FB00-$FFFF - more resources (file types, icons)

($C000-$CFFF is reserved for I/O, and main $BF page and language card is ProDOS)

       Main              Aux               ROM
$FFFF +------------+    +------------+    +------------+
      | ProDOS     |    | DeskTop    |    | Monitor    |
$F800 |            |    | Resources/ |    +------------+
      |            |    | Buffers    |    | Applesoft  |
      |            |    |            |    |            |
      |            |    |            |    |            |
      |            |    |            |    |            |
$D000 +------------+    +------------+    +------------+    +------------+
                                                            | I/O        |
                                                            |            |
$C000 +------------+    +------------+                      +------------+
      | ProDOS     |    | DeskTop    |
$BF00 +------------+    | App Code   |
      | DeskTop    |    |            |
      | App Code   |    |            |
      |            |    |            |
      |            |    |            |
      |            |    |            |
      |            |    |            |
      |            |    |            |
$8E00 |            |    +------------+
      |            |    | A2D GUI    |
      |            |    | Library    |
      |            |    |            |
      |            |    |            |
      |            |    |            |
      |            |    |            |
      |            |    |            |
      |            |    |            |
$4000 +------------+    +------------+
      | Graphics   |    | Graphics   |
      |            |    |            |
      |            |    |            |
      |            |    |            |
      |            |    |            |
      |            |    |            |
      |            |    |            |
      |            |    |            |
$2000 +------------+    +------------+
      | Desk Acc   |    | Desk Acc   |
      |            |    |            |
      |            |    |            |
$0800 +------------+    +------------+
      | Text       |    | Text       |
$0400 +------------+    +------------+
      |            |    |            |
$0300 +------------+    +------------+
      | Input Buf  |    | Input Buf  |
$0200 +------------+    +------------+
      | Stack      |    | Stack      |
$0100 +------------+    +------------+
      | Zero Page  |    | Zero Page  |
$0000 +------------+    +------------+