CP/M-86 4.1 Data Segment

The address of the CP/M data segment is returned in ES:BX by the S_SYSDAT call (9Ah). It is laid out as follows:
Offset	Size	Data		Description
============================================================================
00	DW	cpmfunc_0	; Addresses in the code segment of BDOS 
	DW	cpmfunc_1	; function handlers. Numbers 0,2,4...
	DW	cpmfunc_2	; are genuine; numbers 1,3,5... are 
	...			; dummies and point at "retn" 
	DW	cpmfunc_13	; instrctions.
1C	DB	build_date	; ASCII, 8 bytes
24	DD	bootfunc2	; If this address is nonzero, then it is
				; the address of a function that should
				; be called on boot; perhaps support for 
				; another module like the DOS emulator, or
				; for Resident System Processes.
				; All existing systems seem to have 0 here.
28	DD	xiosentry	; Far pointer to the XIOS main entry.
2C	DD	xiosboot	; Far pointer to the XIOS cold boot routine.	
30	DD	bdosentry	; Far pointer to the internal BDOS call 
				; handler (which should be entered with DS
				; already pointing at this segment and a 
				; local stack).
34	DD	timeslice	; Far pointer to a routine called by the 
				; XIOS when the system tick occurs.
38	DD	sysflag		; Far pointer to a routine called by the
				; XIOS when a system flag changes.
3C	DD	keyboard	; Far pointer to a routine called by the
				; XIOS when keyboard input occurs.
40	DD	dosmod		; Far pointer to the DOS emulator cold 
				; boot function, if present. Else zero. 
44	DW	ccpdseg		; (in the boot file) Paragraph address of
				; the CCP data segment.
				; This is a standard CP/M-86 zero page, ie.
				; it starts with the following data:
				;		DW ccp_codeseg_len
				;		DB 0
				;		DW ccp_codeseg_base_para
				;		DB 0
				;		DW ccp_dataseg_len
				;		DB 0
				;		DW ccp_dataseg_base_para
				;
				; Once the boot file has loaded, this word
				; seems to be used to track memory allocations.
46	DW	cseg		; First paragraph used by the system file
				; (ie, the BDOS code segment)
48	DW	cseg_end	; First paragraph not used by the system file
				; (ie, end of the BDOS data segment)
4A	DW	fgproc	; Segment of process table entry for 
				; foreground process (offset will be 0) 
4C	DW	sysflaglist	; List of processes waiting on system flags
4E	DW	curproc	; Segment of process table entry for
				; current process
50	DW	proctable ; Segment of process table
52	DD	?
56	DB	prcount	 	; Number of processes in the system, 1-4.
57	DW	bdosver		; BDOS version, 1041h
				; (see Interrupt List, AX=4452h)
59	BYTE	?		; System variable 140
5A	DS	4		; CP/M search path - up to 4 drives, terminated
				; with 0FFh if fewer than 4 present.
				; 0 for default drive, 1-16 for A: to P:
5E	DB	tempdrive	; Drive for temporary files
5F	DW	daycount	; Days since 31-12-1977
61	DB	hours		; Time, hours (BCD)
62	DB	minutes		; Time, minutes (BCD)
63	DB	seconds		; Time, seconds (BCD)
64	DB	curx		; Current screen X-coordinate
65	DB	maxx		; Screen width - 1
66	DB	maxy		; Screen height - 1
67	DB	pagemode	; Should programs pause every screenful?
John Elliott 18-9-2000