CP/M survey

Not under CP/M. this is the bios call entry table. ; ; perform following functions ; boot cold start ; wboot warm start (save i/o byte) ; (boot and wboot are the same for mds) ; const console status ; reg-a = 00 if no character ready ; reg-a = ff if character ready ; conin console character in (result in reg-a) ; conout console character out (char in reg-c) ; list list out (char in reg-c) ; punch punch out (char in reg-c) ; reader paper tape reader in (result to reg-a) ; home move to track 00 ; ; (the following calls set-up the io parameter block for the ; mds, which is used to perform subsequent reads and writes) ; seldsk select disk given by reg-c (0,1,2...) ; settrk set track address (0,...76) for subsequent read/write ; setsec set sector address (1,...,26) for subsequent read/write ; setdma set subsequent dma address (initially 80h) ; ; (read and write assume previous calls to set up the io parameters) ; read read track/sector to preset dma address ; write write track/sector from preset dma address ; ; jump vector for indiviual routines jmp boot wboote: jmp wboot jmp const jmp conin jmp conout jmp list jmp punch jmp reader jmp home jmp seldsk jmp settrk jmp setsec jmp setdma jmp read jmp write jmp listst ;list status jmp sectran ; The relevent ones for char IO are conin, conout, constat, list, listst, punch, reader. Disk or any block addressable device is seldsk, settrk, setsec, setdma, read, write and sectran. While the names are descriptive they do not adaquately tell you what the task is. For example SELDSK selects a disk and to do that was do several things like save the number of the drive to be used and return a pointer to a table (DPH or disk parameter table) of addresses of information and scratch areas needed for that disk. One very important address in that table is the DPblock which actually descibes the size, CHS organization and allocation block size of the reference drive. The BDOS uses these to compute the calls to seltrk(set track) and selsec(set sector) that will be used for reading or writing. These are in unix terms the very rawest level device calls. What CP/M is/does is provice three major functions. CCP, console command processor and simple monitor that is the user interface. BDOS, this does "high level" stuff like open a file, get a char, put a char put a char to list device and other filesystem and IO sundries. BIOS, this is the layer that translates a standard set of calls from the BDOS to perform things that are very hardware specific. Modern term is hardware abstraction layer. The bios tried to make the various different disk controllers and connected disks and serial/parallel devices looks like very standardized but elementary IO. What you call a driver in *nix is the BDOS level calls in CP/M for equivilent level of functionality. included is the BDOS command dispatch table from CP/M2 (8080): ; ; command dispatch table DISTBL: DEFW WBOOTF ; 0: System reset DEFW REDCON ; 1: Console input DEFW WRTCON ; 2: Console output DEFW XRQ ; 3: Reader input DEFW XRQ ; 4: Punch output DEFW LISTF ; 5: List output DEFW DIRTIO ; 6: Direct console I/O DEFW GETIOB ; 7: Get I/O Byte DEFW PUTIOB ; 8: Set I/O Byte DEFW PRNBUF ; 9: Print string DEFW REDBUF ; 10: Read console buffer DEFW GCSTAT ; 11: Get console status DEFW GETVER ; 12: Return version number DEFW RESET ; 13: Reset disk system DEFW LOGIN ; 14: Select disk DEFW OPEN ; 15: Open file DEFW CLOSE ; 16: Close file DEFW SEAR1 ; 17: Search for first DEFW SEARN ; 18: Search for next DEFW DELETE ; 19: Delete file DEFW READ ; 20: Read sequential DEFW WRITE ; 21: Write sequential DEFW CREATE ; 22: Make file DEFW RENAME ; 23: Rename file DEFW GLOGIN ; 24: Return login vector DEFW GETDRV ; 25: Return current disk DEFW DMASET ; 26: Set DMA address DEFW GALLOC ; 27: Get addr (alloc) DEFW MAKRO ; 28: Write protect disk DEFW GROVEC ; 29: Get R/O vector DEFW SETATT ; 30: Set file attributes DEFW GETPAR ; 31: Get addr (disk parms) DEFW MODUSR ; 32: Set/Get user code DEFW REDRND ; 33: Read random DEFW WRTRND ; 34: Write random DEFW FILSIZ ; 35: Compute file size DEFW SETRND ; 36: Set random record DEFW RESDRV ; 37: Reset drive DEFW XRQ ; 38: Undefined - go back DEFW XRQ ; 39: Undefined - go back DEFW ZERRND ; 40: Fill random file w/ zeros ; To wrap up: The cpm prompt A:>edit fred.txt causes the CCP to do this>> call bdos open and see if edit exists, if it does it does several read sequential andd loads the read file startin at 100h in memory and jumps to it. *runs edit* That program calls the bdos open to see if fred.txt exits, if yes it loads it's buffer(s) as needed with further bdos calls. IF not then it may create a file entry and allocate a block to it for future storage use. Of course the bdos makes a pile of calls to gets and put characters, check the console device for any keys pressed and outputting characters as well as disk related IO. Very un *nix like. Likely more than anyone wanted to know but while CP/M is pervasive not everyone is familiar or familiar to the code level. Allison