CP/M survey

On Apr 19, 2007, at 3:20 AM, Sridhar Ayengar wrote: All UNIX-ish drivers are. ;) A CP/M BIOS is much simpler than that. Assuming CP/M v2.2 (the only version I've worked with) there are only (IIRC) seventeen routines which must be written, and they're all very low-level. There are console I/O routines like CONIN and CONOUT, which just get/put bytes to/from the console UART in the simplest of implementations, or they may manage buffers and interrupt service routines for more "fancy" serial I/O. There's SELDSK, SETTRK and SETSEC, which set the active disk drive, and track/sector numbers for the next transfer. Then there's READ and WRITE which, in a simple polled/non-DMA BIOS, can be less than half a page of assembly language. To CP/M, every mass storage device looks like a rotating disk with tracks and sectors. There are a few others, again seventeen if memory serves...READER and PUNCH, which are character-by-character reader and punch I/O, etc. There's LIST (printer output), WBOOT (warm boot), BOOT (cold boot)...not much else. So my point is that these routines are lower level and much less generalized than what we'd think of as a device driver in a modern UNIX-based OS. -Dave -- Dave McGuire Port Charlotte, FL