Casio World Open is a 32 KB Casio cartridge from 1985, filling pages 1 and 2 (0x4000-0xBFFF).
The AB header at 0x4000 declares only INIT, at 0x4010. No STATEMENT, no DEVICE, no TEXT.
The title runs in SCREEN 1, the 32-column text mode: the BIOS supplies the font and the colour for the whole screen fits in 32 bytes, one per eight patterns. The game runs in SCREEN 2, used as a bitmap: the name table is the identity map and the picture lives entirely in the pattern table.
Getting from one to the other has a trick. 0x44F3 enters SCREEN 1 only to keep the character set the BIOS has just loaded, copies it to RAM and, once in SCREEN 2, dumps it back as the course's patterns.
There are two handlers. The start-up one (0x415B) is temporary: it calls the real one and, the first time round, finishes the initialisation. The real one (0x44D3) runs the whole game, hooked into H.TIMI.
| bytes | ||
|---|---|---|
| traced code | 8,185 | 24.98 % |
| identified data | 24,583 | 75.02 % |
| unexplained | 0 | 0.00 % |