Using CP/M

CP/M Quick Reference 

Control key commands

CTRL + C	Restarts CP/M by initiating a warm start
CTRL + E	Forces the cursor to the next line of the screen for continued command line input.
CTRL + H	Moves the cursor one space to the left in the same manner as the BS key.
CTRL + I	Inputs a tab code (same as the TAB key)
CTRL + P	Turns on or off the printer echo function. When the printer echo function is turned on, data displayed on the LCD screen is output to the printer (or other device assigned to LST:) each time the RETURN key is pressed. The printer echo function is turned on by pressing CTRL + P once and is turned off when CTRL + P is pressed a second time. (Make sure the printer is connected properly before using this command.)
CTRL + R	Redisplays the contents of the current command line.
CTRL + S	Momentarily stops processing currently being performed (same as the PAUSE key). Processing can be resumed by inputting this command again.
CTRL + U	Cancels the current command line and moves the cursor to the next line on the screen for input of a different command.
CTRL + X	Erases the current command line and moves the cursor back to the beginning of the line.
CTRL + Z	Terminates input from the keyboard (used in combination with certain CP/M transient commands).

Commands

d: - A drive letter
filematch - an exact filename, or a wildcard match for files.
Items such as [item] are optional, ones such as <item> are compulsory.

DIR [d:][filematch]
Display a list of files in the specified, or current drive.

ERA [d:]<filematch>
Erase specified files. filematch *.* can be used to match all files in the current drive.

REN [d:]newname.ext = oldname.ext
Change the name of a disk file from oldname.ext to newname.ext

SAVE n [d:]filename.ext
Save the specified n number of pages of the transient program area to disk under the specified file name.

TYPE [d:]filename.ext
Display the contents of the specified file on the display screen. Display is only meaningful if the file contents was ASCII text.

USER n
Switches to the specified user area in a disk drive.
A user area is a physical area on a disk which has its own directory and which is managed separately from the rest of the disk. Data cannot be read from or written to any user area other than that in which CP/M is currently operating. A disk can be divided up into a maximum of 16 user areas.

PIP

Copy FOO.TXT to console (print).

C:PIP CON:=A:FOO.TXT

Write to file from terminal (CTRL-Z to EOF, CTRL-M+J for new line):

C:PIP FOO.TXT=CON:

Copy file from current drive to A:

C:PIP A:UPLOAD.COM=UPLOAD.COM

ED

• http://www.gaby.de/cpm/manuals/archive/cpm22htm/ch2.htm 
  

Commands mode

#a	load all lines from file (given as arg to the command) to memory
10a	load 10 lines from file
b#t	go to beginning, print all lines
b	go to beginning
n or -n	move n lines ahead/behind and print
t	print current line
k	kill current line
i	insert before current line
e	save and exit
o	discard changes

In insert mode

CTRL + H	backspace one char
CTRL + Z	exit insert mode

ASM

• http://www.gaby.de/cpm/manuals/archive/cpm22htm/ch3.htm#Section_3.6

Compile and run example program:

c:asm example
c:load example
example

Show compiled program listing:

type example.prn

Compiler output line markers

S	syntax error
L	bad label
E	bad expression
R	bad register
Y	bad value

API

• https://www.seasip.info/Cpm/bdos.html
• https://obsolescence.wixsite.com/obsolescence/cpm-internals
• http://www.gaby.de/cpm/manuals/archive/cpm22htm/ch5.htm
  

Entry point: 05h (CALL 05h).

Memory map

File Control Block

FCB start: 5Ch (not 60h as in the picture).

Address	Field	Definition
FCB+00h	dr	drive code (0-16) 0 = use default drive for file 1 = auto disk select drive A, 2 = auto disk select drive B,     ... 16 = auto disk select drive P.
FCB+01h	f1...f8	contain the filename in ASCII upper-case, with high bit = 0
FCB+09h	t1,t2,t3	contain the filetype in ASCII upper-case, with high bit = 0. t1', t2', and t3' denote the bit of these positions, t1' = 1 = Read-Only file, t2' = 1 = SYS file, no DIR list
FCB+0Ch	ex	contains the current extent number, normally set to 00 by the user, but in range 0-31 during file I/O
FCB+0Dh	s1	reserved for internal system use
FCB+0Eh	s2	reserved for internal system use, set to zero on call to OPEN, MAKE, SEARCH
FCB+0Fh	rc	record count for extent ex; takes on values from 0-127; Set this to 0 when opening a file
FCB+10h	d0...dn	filled in by CP/M; reserved for system use
FCB+20h	cr	current record to read or write in a sequential file operation; normally set to zero by user after opening file
FCB+21h	r0,r1,r2	optional random record number in the range 0- 65535, with overflow to r2, r0, r1 constitute a 16-bit value with low byte r0, and high byte r1

File Buffer start: 80h (128 bytes long).

Notes

• When running command in CP/M with file path as first argument the drive number and file name are set in default FCB automatically before program runs.
• When two arguments are given another drive number and file name are set starting from absolute 6Ch. It will be overwritten by file operations.
• If no arguments are given the FCB file name is all blank/space characters ( )
• Command line arguments are also available from 80h (File Buffer).

Useful constants:

FCB       EQU  5Ch     ; File Control Block
FCBFNAME  EQU  FCB+01h ; FCB File Name
FCBEX     EQU  FCB+0Ch ; FCB Excent Number
FCBRC     EQU  FCB+0Fh ; FCB Record Count
FCBCR     EQU  FCB+20h ; FCB Current Record
FB        EQU  80h     ; File Buffer

CP/M procedures

Function Number		Function Name	Input	Output
Dec	Hex
0	0	System Reset	none	none
1	1	Console Input	none	A = ASCII char
2	2	Console Output	E = char	none
3	3	Reader Input	none	A = ASCII char
4	4	Punch Output	E = char	none
5	5	List Output	E = char	none
6	6	Direct Console I/O	E = 0FFH (input)	A = char
			E = 0FEH (status)	A = status
			E = char	none
7	7	Get I/O Byte	none	A = I/O byte value
8	8	Set I/O Byte	E = I/O byte	none
9	9	Print String	DE = Buffer Address	none
10	A	Read Console String	DE = Buffer	Console characters in Buffer
11	B	Get Console Status	none	A = 00/non zero
12	C	Return Version #	none	HL = Version #
13	D	Reset Disk System	none	none
14	E	Select Disk	E = Disk #	none
15	F	Open File	DE = FCB address	A = FF if not found
16	10	Close File	DE = FCB address	A = FF if not found
17	11	Search For First	DE = FCB address	A = Directory Code
18	12	Search For Next	none	A = Directory Code
19	13	Delete File	DE = FCB address	A = none
20	14	Read Sequential	DE = FCB address	A = Error Code
21	15	Write Sequential	DE = FCB Address	A = Error Code
22	16	Make File	DE = FCB address	A = FF if no DIR Space
23	17	Rename File	DE = FCB address	A = FF if not found
24	18	Return Login Vector	none	HL = Login Vector*
25	19	Return Current Disk	none	A = Current Disk Number
26	1A	Set DMA Address	DE = DMA address	none
27	1B	Get ADDR (ALLOC)	none	HL = ALLOC address*
28	1C	Write Protect Disk	none	none
29	1D	Get Read/only Vector	none	HL = ALLOC address*
30	1E	Set File Attributes	DE = FCB address	A = none
31	1F	Get ADDR (Disk Parms)	none	HL = DPB address
32	20	Set/Get User Code	E = 0FFH for Get	A = User Number
			E = 00 to 0FH for Set	none
33	21	Read Random	DE = FCB address	A = Error
34	22	Write Random	DE = FCB address	A = Error Code
35	23	Compute File Size	DE = FCB address	r0, r1, r2
36	24	Set Random Record	DE = FCB address	r0, r1, r2
37	25	Reset Drive	DE = Drive Vector	A = 0
38	26	Access Drive	not supported
39	27	Free Drive	not supported
40	28	Write Random w/Fill	DE = FCB	A = error code

Reading file

Given file name in the arguments one can first check if argument was given by checking for space character in FCBFNAME (FBC + 01h).

If file name is filled we can open the file:

     XOR  A
     LD   (FCBEX),A   ; select 0'th extent
     LD   (FCBRC),A   ; clear
     LD   (FCBCR),A   ; clear
     LD   C,FOPE      ; open file
     LD   DE,FCB      ; use default FCB
     CALL BDOS

Set EX, RC and CR to 0 and call File Open (0Fh). A will contain FFh if file was not found.

Next file can be read:

     XOR  A
     LD   (FCBCR),A ; start from beginning
     LD   C,FRED    ; read file
     LD   DE,FCB    ; use default FCB
     CALL BDOS

Set CR to 0 to start reading from beginning of the file and call Read Sequential (14h). A is set to 0 if read was successful.

128 bytes was read to FB (starting at 80h). CR (and EX) will be automatically incremented, so calling Read Sequential again will read next 128 byte of the file to FB.