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272 lines
11 KiB
Markdown
272 lines
11 KiB
Markdown
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# DeskTop diassembly notes - DESKTOP2.$F1
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This is large - 111k. It includes a loader and the DeskTop app with
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both main memory and aux memory segments, filling everything from
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$4000 to $FFFF (except for I/O space and ProDOS), and still having
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more code segments swapped in dynamically.
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The file is broken down into multiple segments:
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| Purpose | File Offset | Bank | Address | Length | Sources |
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|---------------|-------------|--------|--------------|--------|--------------------------------|
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| Loader | B$000000 | Main | A$2000-$257F | L$0580 | `loader.s` |
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| MGTK/DeskTop | B$000580 | Aux | A$4000-$BFFF | L$8000 | `mgtk.s`, `desktop_aux.s` |
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| DeskTop | B$008580 | Aux LC | A$D000-$ECFF | L$1D00 | `desktop_lc.s`,`desktop_res.s` |
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| DeskTop | B$00A280 | Aux LC | A$FB00-$FFFF | L$0500 | `desktop_res.s` |
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| DeskTop | B$00A780 | Main | A$4000-$BEFF | L$7F00 | `desktop_main.s` |
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| Initializer | B$012680 | Main | A$0800-$0FFF | L$0800 | `desktop_main.s` |
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| Invoker | B$012E80 | Main | A$0290-$03EF | L$0160 | `invoker.s` |
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| Disk Copy 1/4 | B$012FE0 | Main | A$0800-$09FF | L$0200 | `ovl1.s` |
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| Disk Copy 2/4 | B$0131E0 | Main | A$1800-$19FF | L$0200 | `ovl1a.s` |
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| Disk Copy 3/4 | B$0133E0 | Aux LC | A$D000-$F1FF | L$2200 | `ovl1b.s` |
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| Disk Copy 4/4 | B$0155E0 | Main | A$0800-$12FF | L$0B00 | `ovl1c.s` |
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| Format/Erase | B$0160E0 | Main | A$0800-$1BFF | L$1400 | `ovl2.s` |
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| Selector 1/2 | B$0174E0 | Main | A$9000-$9FFF | L$1000 | `ovl3.s` |
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| Common | B$0184E0 | Main | A$5000-$6FFF | L$2000 | `ovl4.s` |
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| File Copy | B$01A4E0 | Main | A$7000-$77FF | L$0800 | `ovl5.s` |
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| File Delete | B$01ACE0 | Main | A$7000-$77FF | L$0800 | `ovl6.s` |
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| Selector 2/2 | B$01B4E0 | Main | A$7000-$77FF | L$0800 | `ovl7.s` |
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(EOF is $01BCE0)
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The DeskTop segments loaded into the Aux bank switched ("language
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card") memory can be used from both main and aux, so contain relay
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routines, resources, and buffers. More details below.
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## Structure
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### Loader
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`loader.s`
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Invoked at $2000; patches the ProDOS QUIT routine (at LC2 $D100) then
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invokes it. That gets copied to $1000-$11FF and run by ProDOS.
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The invoked code stashes the current prefix and re-patches ProDOS with
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itself. It then (in a convoluted way) loads in the second $200 bytes of
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`DESKTOP2` at $2000 and invokes that.
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This code then loads the rest of the file as a sequence of segments,
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moving them to the appropriate destination in aux/banked/main memory.
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There's fourth chunk of code, which expects to live at $280 so it
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can't co-exist with the Invoker; it may be temporary code, as there is
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no sign that it is ever moved into place. It's also unclear how it
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would be hooked in. The routine detects OA+SA+P and prints the DHR
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screen to an ImageWriter II printer attached to Slot 1. (This may have
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been used to produce screenshots during development for manuals.)
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### Invoker
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`invoker.s`
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Loaded at $290-$03EF, this small routine is used to invoke a target,
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e.g. a double-clicked file. System files are loaded/run at $2000,
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binary files at the location specified by their aux type, and BASIC
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files loaded by searching for BASIC.SYSTEM and running it with the
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pathname passed at $2006 (see ProDOS TLM).
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### Initializer
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(in `desktop_main.s`)
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Loaded at $800-$FFF, this does one-time initialization of the
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DeskTop. It is later overwritten when any desk accessories are
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run.
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### MouseGraphics ToolKit (MGTK)
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`mgtk.s`
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Aux $4000-$8580 is the [MouseGraphics ToolKit](../mgtk/MGTK.md) - a
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GUI library used for the DeskTop application.
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Since this resides in Aux memory, DeskTop spends most of its time
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with Aux read/write enabled. The state and logic for rendering
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the desktop and window contents resides in Aux to avoid proxying
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data.
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### "DeskTop" Application
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`desktop.s` which includes in:
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* `desktop_aux.s`
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* `desktop_lc.s`
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* `desktop_res.s`
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* `desktop_main.s`
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DeskTop application code is in the lower 48k of both Aux and Main:
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* Aux $8580-$BFFF - sitting above the GUI library (`desktop_aux.s`)
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* Main $4000-$BEFF (`desktop_main.s`)
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...and in the Aux language card area (accessible from both aux and
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main code) are relays, buffers and resources:
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* Aux $D000-$D1FF - main-to-aux relay calls
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* Aux $D200-$ECFF - resources (menus, strings, window)
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* Aux $ED00-$FAFF - hole for data buffer - entries for each icon on desktop/in windows
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* Aux $FB00-$FFFF - more resources (file types, icons)
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($C000-$CFFF is reserved for I/O, and main $BF page and language card is ProDOS)
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`desktop_res.s` defines these common resources. It is built as part of
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`desktop.s`. Many additional resources needed for MGTK operations
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exist in `desktop_aux.s` as well.
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The DeskTop code in Aux primarily implements the actual desktop GUI,
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drawing file icons in windows, volume icons on the desktop, handling
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selection and dragging, and tracking icons in windows; this code is
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implemented as a library with MLI-style calls. The code in Main
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handles the bulk of the application logic.
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When running, lower memory use includes:
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* Main $800-$1BFF is used as scratch space for a variety of routines.
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* Main $1C00-$1FFF is used as a 1k ProDOS I/O buffer.
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* Aux $0800-$1AFF is a "save area"; used by MGTK to store the background
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when menus are drawn so it can be restored without redrawing. The
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save area is also used by DeskTop to save the background for alert
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dialogs, and icon outlines when dragging.
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* Aux $1B00-$1F7F holds lists of icons, one for the desktop then one for up
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to 8 windows. First byte is a count, up to 127 icon entries. Icon numbers
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map indirectly into a table at $ED00 that holds the type, coordinates, etc.
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* Aux $1F80-$1FFF is a map of used/free icon numbers, as they are reassigned
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as windows are opened and closed.
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### Overlays
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`ovl1.s` etc
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Interactive commands including disk copy/format/erase, file
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copy/delete, and Selector add/edit/delete/run all dynamically load
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main memory code overlays. When complete, any original code above
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$4000 is reloaded (unless a full restart is required.)
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Several of the overlays also use a common file selector dialog overlay
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`ovl4.s` ($5000-$6FFF).
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#### Disk Copy Overlay
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The Disk Copy command replaces large chunks of memory and is best
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thought of as a separate application.
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The first part (`ovl1.s`, $800-$9FF) loads into main memory the other
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overlays, but in turn it loads a second short ($200-byte) overlay
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(`ovl1a.s`, $1800-$19FF). This then loads a replacement for the
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resources in the aux language card area (`ovl1b.s`, Aux LC
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$D000-$F1FF) and another block of code in main memory (`ovl1c.s`, Main
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$0800-$12FF). When exiting, the DeskTop is restarted from the
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beginning.
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#### Disk Format/Disk Erase
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Simple overlay: `ovl2.s`, loaded into Main A$0800-$1BFF.
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#### Selector - Delete Entry / Run Entry
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Simple overlay: `ovl3.s` ($9000-$9FFF).
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#### Selector - Add Entry / Edit Entry
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Also uses `ovl3.s` ($9000-$9FFF) but additionally uses overlay
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`ovl7.s` ($7000-$77FF) and the file selector dialog `ovl4.s`
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($5000-$6FFF).
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#### File Copy
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Overlay `ovl5.s` ($7000-$77FF), uses file selector dialog `ovl4.s`
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($5000-$6FFF).
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#### File Delete
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Overlay `ovl6.s` ($7000-$77FF), uses file selector dialog `ovl4.s`
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($5000-$6FFF).
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## Memory Map
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```
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Main Aux ROM
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$FFFF +-------------+ +-------------+ +-------------+
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| ProDOS | | DeskTop | | Monitor |
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$F800 | | | Resources/ | +-------------+
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| | | Buffers | | Applesoft |
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| |Bank2 | |Bank2 | |
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$E000 | +----+ | +----+ | |
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| | PD | | | xx | | |
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$D000 +-------------+----+ +-------------+----+ +-------------+
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| I/O |
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$C000 +-------------+ +-------------+ +-------------+
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| ProDOS GP | | DeskTop |
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$BF00 +-------------+ | App Code |
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| DeskTop | | |
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| App Code | | |
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$A000 | +------+ | |
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| | Ovl | | |
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$9000 | +------+ | |
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$8E00 | | | Entry Point |
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$8800 | | | Font |
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$8580 | | +-------------+
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| | | MGTK |
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$7800 | +------+ | |
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| | Ovl | | |
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$7000 | +------+ | |
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| | Ovl | | |
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$5000 | +------+ | |
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$4000 +-------------+ +-------------+
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| Graphics | | Graphics |
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$2000 +-------------+ +-------------+
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| Initializer | | Win/Icn Map |
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$1B00 | & Desk Acc | +-------------+
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| & Overlays | | Desk Acc & |
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| | | Save Area |
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$0800 +-------------+ +-------------+
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| Drawing | | Drawing |
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| Temp Buffer | | Temp Buffer |
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$0400 +-------------+ +-------------+
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| Invoker | | |
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$0300 +-------------+ +-------------+
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| Input Buf | | Input Buf |
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$0200 +-------------+ +-------------+
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| Stack | | Stack |
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$0100 +-------------+ +-------------+
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| Zero Page | | Zero Page |
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$0000 +-------------+ +-------------+
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```
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Memory use by the Disk Copy overlay is not shown.
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