Appendix D: CP/M Cheat Sheet

Note

This cheat sheet summarizes the essential commands for CP/M (Control Program for Microcomputers), the first disk operating system for personal computers. It covers the core built-in commands, important control keys, and a quick reference to the BDOS (Basic Disk Operating System) functions.

Control Keys

CP/M uses several control keys for system interaction. To use them, hold the CTRL key and press the appropriate letter.

Key	Function
CTRL-C	Re-initialize the system. Use after changing diskettes so CP/M recognizes the new disk.
CTRL-P	Toggle printer echo on/off. When active, all console output is also sent to the printer.
CTRL-S	Pause screen output (freeze scrolling). Press any key to resume.
CTRL-X	Erase the current command line.
CTRL-U	Delete the entire current line.
CTRL-R	Retype the current command line on a new line.
CTRL-E	Physical end of line (carriage return without executing the command)[citation:6].
RUBOUT / DEL	Delete and echo the last character typed.

Built-in Commands

These commands are part of the CCP (Console Command Processor) and are available directly from the CP/M prompt (e.g., A>).

Command	Function
DIR drive:	Display a list of files on the specified disk. If no drive given, uses current drive.
DIR *.ext	Use wildcards to list specific files (e.g., DIR *.TXT shows all text files).
ERA filename	Erase (delete) a file from disk.
REN newname=oldname	Rename a file. Include drive if needed.
TYPE filename	Display a text file on the console.
STAT filename	Report file size or remaining disk space. STAT A: shows space on drive A.
PIP	Peripheral Interchange Program: copy or move files between devices and disks.
SYSGEN	Write a copy of CP/M to a disk (to make it bootable).
SAVE n filename.com	Save n pages (256 bytes each) from memory to a disk file.
USER n	Change to a different user area (0-15) for file organization.
drive:	Change the logged-in drive. For example, typing B: switches to drive B.

Hint

Filenames in CP/M follow the 8.3 format: up to 8 characters, a dot, and a 3-character extension (e.g., REPORT.TXT). Drive identifiers are letters followed by a colon (e.g., B:).

BDOS Function Calls (Programmer’s Reference)

The BDOS provides system services via function calls. Programs invoke these by loading the function number into register C and calling address 0005H

Common Function Codes

Code	Function Name	Description
0	System Reset	Return control to the CCP (warm boot).
1	Console Input	Read a character from the console, echo it.
2	Console Output	Output a character to the console.
5	List Output	Output a character to the list device.
6	Direct Console I/O	Direct character I/O (no control char handling) - E=FFh: input, returns char, 0 if none - E=FEh: status, returns FF if ready - E=char: output char
9	Print String	Output a string terminated by $
10	Read Console Buffer	Read an edited line into a buffer
11	Get Console Status	Check if a character is ready (return 01 if yes)
12	Return Version	Return CP/M version number in HL
13	Reset Disk System	Reinitialize disk system
14	Select Disk	Select the default disk (E = drive #)
15	Open File	Open a file via FCB (File Control Block)
16	Close File	Close a file via FCB
19	Delete File	Delete a file via FCB
20	Read Sequential	Read next record from an open file
21	Write Sequential	Write next record to an open file
23	Rename File	Rename a file via FCB
25	Get Current Disk	Return current default disk number in A

Important

Many BDOS functions use a File Control Block (FCB) structure. The default FCB for command-line arguments is at address 5CH, and the default DMA (Disk Memory Access) buffer is at 80H.

PIP (Peripheral Interchange Program) Options

PIP is a powerful utility for copying and transferring files. It supports several options (typed after the command):

Option	Function
V	Verify copy operation (check for errors)
U	Translate lowercase to uppercase
L	Translate uppercase to lowercase
N	Add line numbers to output
E	Echo transferred data to the console
F	Remove form feeds from the file
T n	Expand tabs to n spaces

Common PIP Examples:

• PIP B:=A:FILENAME.TXT – Copy a single file from drive A to drive B.

• PIP B:=A:*.* – Copy all files from drive A to drive B.

• PIP PRN:FILENAME.TXT – Send a file to the printer.

Quick Reference Card

Need To…	Type This
See what’s on a disk	DIR
Delete a file	ERA FILENAME.EXT
Rename a file	REN NEWNAME.EXT=OLDNAME.EXT
View a text file	TYPE DOCUMENT.TXT (use CTRL-S to pause)
Copy a file	PIP B:=A:DATA.DAT
Switch drives	B: (or any drive letter)
Check disk space	STAT A: