iz-cpm — CP/M 2.2 environment

What is this?

This is a CP/M 2.2 execution environment. It provides everything needed to run a standard CP/M for Z80 or 8080 binary.

Uses my iz80 library for Zilog Z80 and Intel 8080 emulation.

Made with Rust

Note that iz-cpm is a very basic implementation, mostly for educational purposes. I recommend MockbaTheBorg’s RunCPM or Udo Munk’s Z80pack for a much more complete CP/M emulation.

Installation

Extract the latest zip for Linux, MacOS or Windows. Optionally run download.sh or download.bat to download the CP/M 2.2 system disk, Microsoft Basic, Turbo Pascal, Lisp and some games.

Build from source

To build from source, install the latest Rust compiler, clone the repo and run cargo build --release. To cross compile to Windows, install the target with rustup and run cargo build --release --target x86_64-pc-windows-gnu.

Usage examples

Execute iz-cpm to open the CP/M command prompt (the CCP) on the current directory:

casa@servidor:~/software/cpm22$ ls
ASM.COM      CCSINIT.COM   DISKDEF.LIB  iz-cpm        STAT.COM
CBIOS.ASM    CCSYSGEN.COM  DUMP.ASM     LOAD.COM      STDBIOS.ASM
CCBIOS.ASM   CPM24CCS.COM  DUMP.COM     MOVCPM.COM    SUBMIT.COM
CCBOOT.ASM   DDT.COM       ED.COM       PIP.COM       SYSGEN.COM
-CCSCPM.251  DEBLOCK.ASM   GENMOD.COM   RLOCBIOS.COM
casa@servidor:~/software/cpm22$ ../../iz-cpm 
iz-cpm https://github.com/ivanizag/iz-cpm
CP/M 2.2 Copyright (c) 1979 by Digital Research
Press ctrl-c ctrl-c to return to host
A>dir
A: CCSINIT  COM : MOVCPM   COM : CPM24CCS COM : STAT     COM
A: SYSGEN   COM : STDBIOS  ASM : IZ-CPM       : LOAD     COM
A: DISKDEF  LIB : ASM      COM : RLOCBIOS COM : DUMP     COM
A: -CCSCPM  251 : CCBIOS   ASM : DUMP     ASM : CCSYSGEN COM
A: DEBLOCK  ASM : ED       COM : SUBMIT   COM : DDT      COM
A: PIP      COM : CBIOS    ASM : CCBOOT   ASM : GENMOD   COM
A>

Execute iz-cpm with a file to execute a CP/M binary directly, bypassing the CPP:

casa@servidor:~$ ./iz-cpm software/OBASIC.COM 
44531 Bytes free
BASIC Rev. 4.51
[CP/M Version]
Copyright 1977 (C) by Microsoft
Ok
print "hello"
hello
Ok

Map up to 16 directories as CP/M drives:

casa@servidor:~$ ./iz-cpm --disk-a software/cpm22 --disk-b software/zork --disk-e .
iz-cpm https://github.com/ivanizag/iz-cpm
CP/M 2.2 Copyright (c) 1979 by Digital Research
Press ctrl-c ctrl-c to return to host
A>b:
B>dir
B: ZORK2    DAT : ZORK1    COM : ZORK3    DAT : ZORK3    COM
B: FILE_ID  DIZ : ZORK1    DAT : ZORK1    SAV : ZORK2    COM
B>zork1
ZORK I: The Great Underground Empire
Copyright (c) 1981, 1982, 1983 Infocom, Inc. All rights
reserved.
ZORK is a registered trademark of Infocom, Inc.
Revision 88 / Serial number 840726
West of House
You are standing in an open field west of a white house, with
a boarded front door.
There is a small mailbox here.
>

Usage

iz-cpm https://github.com/ivanizag/iz-cpm
CP/M 2.2 Copyright (c) 1979 by Digital Research
Press ctrl-c ctrl-c to return to host 
USAGE:
    iz-cpm [FLAGS] [OPTIONS] [ARGS]
FLAGS:
    -t, --call-trace        Traces BDOS calls excluding screen I/O
    -T, --call-trace-all    Traces BDOS and BIOS calls
    -z, --cpu-trace         Traces Z80 instructions execution
    -h, --help              Prints help information
    -s, --slow              Runs slower
    -V, --version           Prints version information
OPTIONS:
        --cpu <model>            cpu model z80 or 8080 [default: z80]
    -a, --disk-a <path>          directory to map disk A: [default: .]
    -b, --disk-b <path>          directory to map disk B:
    -c, --disk-c <path>          directory to map disk C:
    -d, --disk-d <path>          directory to map disk D:
        --disk-e <path>          directory to map disk E:
        --disk-f <path>          directory to map disk F:
        --disk-g <path>          directory to map disk G:
        --disk-h <path>          directory to map disk H:
        --disk-i <path>          directory to map disk I:
        --disk-j <path>          directory to map disk J:
        --disk-k <path>          directory to map disk K:
        --disk-l <path>          directory to map disk L:
        --disk-m <path>          directory to map disk M:
        --disk-n <path>          directory to map disk N:
        --disk-o <path>          directory to map disk O:
        --disk-p <path>          directory to map disk P:
        --terminal <terminal>    Terminal emulation ADM-3A or ANSI [default: adm3a]
ARGS:
    <CMD>     The binay image to run, 
    <ARGS>    Parameters for the given command

Features

Execution of 8080 and Z80 binaries on top of CP/M
Direct usage of the host computer filesystem
Terminal emulation of ADM-3A as used in the KAYPRO computers
Z80 emulation validated with ZEXALL
CPU execution tracing
BDOS and BIOS tracing
Portable, runs in Linux, MacOS and Windows. Mmm, not in CP/M.

How does it work

CP/M was designed to be portable to a variety of devices using Intel 8080, Intel 8085 or Zilog Z80 processors thanks to a tiered architecture. The main parts of CP/M are:

The BIOS: Basic Input/Output system. Interface with the hardware. CP/M defines a very small interface: 16 entrypoints to manage I/O and access to disk sectors. The hardware vendors provided the BIOS for their device based on source code available on the CP/M distribution.
The BDOS: Basic Disk Operating System. Main component of CP/M. Provided by Digital Research and common to all systems. Provides the high level entrypoints to be used by application developpers.
The CCP: Console Command Processor. The CP/M Command prompt.

To emulate this environment using the host filesystem, we have to provide a replacement BDOS translating as we don’t want to relay on the physical disk sectors abstraction of the BIOS. The main components are:

Z80 emulator. It uses iz80
BIOS emulator. Only the I/O entrypoints. In theory, it shouldn’t be necessary, but some programs use it directly, bypassing BDOS.
BDOS emulator. Traps the calls and executes code on the host.
CPP. Runs natively, no emulation needed. We use ZCPR1 an open source alternative. See cpmish for other open source alternatives to the CP/M binaries. The CPP binary from CP/M 2.2 can be used optionally.
Terminal emulator. CP/M does not define how the terminal should work. Applications needed to be aware and usually could be configured for several leading options, like ADM-3a, VT-52, Hazeltine 1500 and Osborne. This emulator supports ADM-3a used also on the very popular Kaypro computers.

Useful links:

TODO

Proper documentation
File level read-only option (I won’t do that, the host can control that)
BIOS support for punch cards (Nope)
BIOS support for track/sector access to disks (Not needed)