WonderWitch/Process
Memory layout
Process memory is stored in SRAM banks 3 (process 0 - typically used by FreyaOS), 2 (process 1) and 1 (process 2). The entire bank is available to the process.
Process control block
The process control block contains information about the running process. It is stored in the first 96 bytes of data.
| Offset | Length | Contents |
|---|---|---|
| 0 | 4 | Compiler ID, zero-terminated string; see below |
| 4 | 2 | TODO |
| 6 | 2 | TODO |
| 8 | 2 | TODO |
| 10 | 2 | TODO |
| 12 | 4 | Far pointer to IlibIL library |
| 16 | 4 | Far pointer to ProcIL library |
| 20 | 4 | TODO |
| 24 | 64 | Current working directory of the process |
| 88 | 2 | Near pointer to an array of near pointers to arguments (argv) |
| 90 | 4 | Far pointer to the process's resource data |
| 94 | 2 | Near pointer to the beginning of the process's free heap area. |
Compiler IDs
| ID | Compiler | Source |
|---|---|---|
LCC |
LSI C | WonderWitch SDK |
TCC |
Turbo C/C++ | WonderWitch SDK |
DMC |
Digital Mars C | WonderWitch SDK (newer versions) |
GCC |
gcc-ia16 | Wonderful Toolchain |
TCC |
Visual C++ | WonBe |
Launching procedure
Launching a process is split into two stages: loading and running.
Load
The load routine begins at offset 0 into the application. It performs the following activities:
- SRAM initialization: copying static data from ROM to SRAM and zeroing SRAM memory,
- copying the compiler ID to the PCB,
- heap initialization: setting the argv and heap pointers to the location of the first free byte in SRAM,
- returning in AX a near pointer to the start function (see "Run").
Run
The start function is of the form void main(int argc, char* argv);. It typically performs the following activities before jumping to C code:
- configuring the stack pointer, - resetting the display (disabling screen/sprite layers, clearing window and sprite configuration, resetting scroll), - initializing screen/sprite VRAM locations according to user needs (one/two screens, 256/512 free tiles), - initializing the default display settings (configuring text mode, enabling screen layers).
After running C code, INT $10 is triggered to exit the process.
