6.4 KiB
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 - address $2000-$257F, length $0580, file offset $000000 (Loader)
- segment 1: aux1 - address $4000-$BFFF, length $8000, file offset $000580 (A2D, part of DeskTop)
- segment 2: aux2 - address $D000-$ECFF, length $1D00, file offset $008580 (More of DeskTop)
- segment 3: aux3 - address $FB00-$FFFF, length $0500, file offset $00A280 (More of DeskTop)
- segment 4: main - address $4000-$BEFF, length $7F00, file offset $00A780 (More of DeskTop)
- segment 5: main - address $0800-$0FFF, length $0800, file offset $012680 (Initializer)
- segment 6: main - address $0290-$03EF, length $0160, file offset $012E80 (Invoker)
- segment N: TBD - 38k so must be further subdivided. Disk Copy, and ...???
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 with
itself. It then (in a convoluted way) loads in the second $200 bytes of
DESKTOP2 at $2000 and invokes that.
This code then loads the rest of the file as a sequence of segments, moving them to the appropriate destination in aux/banked/main memory.
There's fourth chunk of code, which expects to live at $280 so it can't co-exist with the Invoker; it may be temporary code, as there is no sign that it is ever moved into place. It's also unclear how it would be hooked in. The routine detects OA+CA+P and prints the DHR screen to an ImageWriter II printer attached to Slot 1. (This may have been used to produce screenshots during development for manuals.)
Invoker
invoker.s
Loaded at $290-$03EF, this small routine is used to invoke a target, e.g. a double-clicked file. System files are loaded/run at $2000, binary files at the location specified by their aux type, and BASIC files loaded by searching for BASIC.SYSTEM and running it with the pathname passed at $2006 (see ProDOS TLM).
Initializer
desktop.s
Loaded at $800-$FFF, this does one-time initialization of the DeskTop. It is later overwritten when any desk accessories are run.
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
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Font is at $8800
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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 |
| | | | | |
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| | | | | |
$D000 +-------------+ +-------------+ +-------------+ +-------------+
| I/O |
| |
$C000 +-------------+ +-------------+ +-------------+
| ProDOS GP | | DeskTop |
$BF00 +-------------+ | App Code |
| DeskTop | | |
| App Code | | |
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$8E00 | | +-------------+
| | | A2D GUI |
| | | Library |
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$4000 +-------------+ +-------------+
| Graphics | | Graphics |
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$2000 +-------------+ +-------------+
| Initializer | | Desk Acc |
| & Desk Acc | | |
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$0800 +-------------+ +-------------+
| Text | | Text |
| | | |
$0400 +-------------+ +-------------+
| Invoker | | |
$0300 +-------------+ +-------------+
| Input Buf | | Input Buf |
$0200 +-------------+ +-------------+
| Stack | | Stack |
$0100 +-------------+ +-------------+
| Zero Page | | Zero Page |
$0000 +-------------+ +-------------+