Devlog #021 - The Boot Sequence Decoded

The Wall Before the Game

Every time Darklands starts, a sequence of things has to go right before the player sees anything useful. The text banner. The memory check. The graphics mode switch. The sound driver. If any of them fail, the game simply stops.

Until now, this startup chain was one of the least-documented areas of the codebase. We’ve spent the last several sessions filling it in, function by function.

Here’s what we know.

Stage 1: Text-Mode Banner

The very first visible output from Darklands is a text-mode banner: white text on black, rendered before the VGA mode switch. This is handled by the startup function at 1699:0114.

The function draws a blank top row from DS:0C03, then walks an offset table at A895 into a structure called BANNER.DAT. Each entry in that table is a cumulative delta into the file, and the walk renders banner rows through the helper at 0C6D:00A9.

BANNER.DAT is not a bitmap or a font file. It is a compact offset-indexed resource with 20 entries, a simple but functional way to store multiple text-mode rows without a fixed-width slot scheme.

The function 1699:0114 is not a leaf routine. It is called from the pre-banner startup wrapper at 1699:0022, which also pushes the process argument list (argc/argv) into position. So this function receives the command line and acts on it.

Stage 2: Config File and Sound Driver

After the banner is painted, 1699:0114 opens the startup config file config.drk with mode "rb". If the open succeeds, it reads 8 bytes into DS:A86E.

On a real installation, those 8 bytes are: 04 00 20 02 05 00 01 00. The first byte is a driver index.

The driver index maps to a letter through a table of one-byte strings:

Index 1 → letter p → psound.dlc. That letter is appended to the string "sound.dlc" in a result buffer at DS:A876. On a typical install, DS:A876 = "psound.dlc", confirmed by runtime inspection.

If config.drk is missing, the fallback is nsound.dlc at DS:0C14.

Stage 3: Command-Line Switches

After resolving the config-based default, the function scans the remaining argv entries for startup switches beginning with - or /. Three switch shapes are now confirmed:

• /A: takes the next character and builds a ?sound.dlc override name; tries to open the chosen driver file and reports an error if it is missing.
• /O: sets a startup flag at DS:0BF4; later used in the memory check stage as a low-memory override.
• /Q: sets a word at DS:0BF2; runtime-confirmed to skip the intro/presentation sequence.

The /Q switch was verified live: launching darkland.exe /Q reaches the parser with argc = 2, sets 0BF2 = 0001, still selects psound.dlc, and still reaches the sound-driver load at 1699:067B. But it skips the intro PAN sequence entirely when the flag is checked later in the presentation path.

Stage 4: Memory Check

The function at 1699:0522 calls a helper (1699:1150) before handing off to the graphics bootstrap. This helper is the memory check stage.

It checks two things:

EMS memory: Free EMS pages must be at least 0x000B (176 KiB). If not, it prints entry 19 from the BANNER.DAT table and aborts.

Conventional memory: The required amount depends on the selected sound driver:

The full formula is current_program_block_bytes + 0x4B6B0 + driver_delta. If the machine falls short, it prints entries 15..18 and may abort, unless /O is set, which forces the memory report but allows startup to continue.

On a /O probe run, the helper printed a negative additional needed value, which is only possible because /O forces the block unconditionally.

Stage 5: Graphics Bootstrap

After the memory check, the startup wrapper calls 1699:052A, the graphics/bootstrap stage. This is where Darklands crosses from text mode into the game’s VGA presentation environment.

The function opens fonts.fnt and mgraphic.exe. A helper at 0C9F:07CE loads mgraphic.exe using INT 21h / AX=4B03, not as a standalone EXE to run and exit, but as a callable module that gets installed into the running process. Mouse state is initialized through INT 33h immediately after.

mgraphic.exe is a MicroProse graphics/blit dispatch module. misc.exe (loaded earlier, before the banner stage) is the input dispatch module. Together they form a two-part helper layer that the main game calls through trampolines rather than implementing in the main binary.

After the module is in place, the function performs a VGA mode switch to mode 13h (320×200, 256 colours), then handles a split:

• EMS available: allocates graphics buffer through the EMS interface at 0E1B:00F3/0117/00A9, stores the result in C105.
• EMS unavailable: falls back to 0C9F:04C7(1), also stored in C105.

The result is the staging buffer for the presentation system.

Stage 6: COMMONSP.IMG

After the graphics buffer is set up, the helper 1699:179A0 loads commonsp.img.

This is a compact common-sprites bank. Its layout:

• Word 0x0000: payload length (0x0FD0 = 4048 bytes)
• Words 0x0002..0x001C: 14 payload-relative offsets for internal slices
• Payload (14 slices, 0x001E bytes into file)

The 14 slices range from tiny 2-byte entries to a 3,807-byte body. The large body is dominated by palette-range bytes (0x96..0x9F) and contains named compact image records. Embedded labels like HALLEN, CORIDO, KBATLMN, and BCHANGE are followed by dimension bytes and pixel data, a bank of compact named shapes used throughout the game.

The startup code registers this bank through 0DDD:0004 (a shared object-allocation service), stores the returned handle at 9C42, and seeds 13 globals in the A2xx/A3xx/A6xx regions from the file’s offset table. The count is an exact match: 13 non-zero offsets in the file header, 13 rebased startup globals.

Stage 7: Sound Driver Activation

Also inside 1699:052A, the earlier-selected sound driver is finally loaded:

1699:06FE  push 0000
1699:06FE  push A876
1699:06FE  call 0C9F:07CE

The same module-loader helper that loaded mgraphic.exe now loads psound.dlc (or whichever driver was selected). The returned segment is stored at 9417, and the loaded module is registered through 0C9F:08C8. The config bytes from A86E..A874 are then passed into the sound driver’s initialization entry.

The Confirmed Boot Order

From runtime file-open tracing, the complete sequence is:

1. misc.exe: input helper module
2. banner.dat: text-mode banner
3. config.drk: sound driver selection
4. mgraphic.exe + fonts.fnt: graphics module install
5. VGA mode 13h switch
6. commonsp.img: common sprite bank
7. psound.dlc: sound driver activation
8. opendark.dgt + opening2.PAN … opening9.PAN: intro presentation
9. msgfiles, darkland.lst, darkland.cty, etc.: game data

The function 1699:052A spans stages 4–7. Everything after it belongs to the intro presentation layer, which is its own story.

What Remains Open

• The exact role of 0C6D:0100, which sits between the text-mode helper and the graphics bootstrap.
• The exact registration semantics of the CnnmSp tag string used when loading commonsp.img.
• How the graphics bootstrap hands off into the intro PAN player overlay family.