Runtime Memory Map

Runtime Memory Map

Runtime Memory Map and Thunks

A4 Workspace

A4 is anchored at fixed address $7FFE and used as the global state base.

Known Fields (partial)

• A4-$860E: current screen/mode id
• A4-$861A: previous screen/mode id
• A4-$8610, A4-$860F: map/player coordinates
• A4-$864F: last input key
• A4-$864E: new-game flag
• A4-$8617: first-time/modal control flag
• A4-$861B: busy/modal status
• A4-$86B0: exit request (ESC path)
• A4-$85E6: draw context pointer
• A4-$EEF4: loaded map/event blob pointer

Calendar / Era State (see 13-time-era-calendar.md)

• A4-$79B4: sub-day time accumulator (256 units = 1 day)
• A4-$79B6: current era/timeline index (0..9)
• A4-$79DE[era]: day-of-year counter (1..180), 10-word array
• A4-$79CA[era]: year counter (capped at 999 → year 1000), 10-word array
• A4-$79B1: month/sign byte for date display

Engine Thunks (JSR -$xxxx(A4))

Likely private jump-table entries initialized during startup:

• -$83C2: frame/input pump
• -$83CE: set/update mode
• -$83E0: draw glyph/tile
• -$842E: read key
• -$8440: delay/tick sleep
• -$8392, -$8398: map rendering helpers
• -$802C: major engine init
• -$8140: print string
• -$8158, -$815E, -$8146: display pipeline setup

DOS/Exec Wrappers

• LAB_2567C: AllocMem (JMP -198(A6))
• LAB_254BC, LAB_254CC, LAB_254F4: DOS-related wrappers through saved base pointers

Decomp Guidance

• Treat thunk ids as symbolic API names first.
• Keep offsets and unknown fields explicit until strongly inferred.