ZCPR-D&J Fixes

Lars Nelson found a couple issues with ZCPR-D&J and provided an update:

- Buffer overflow
- Failure of default drive/user

Source/ZCPR-DJ/Build.cmd

@@ -10,4 +10,7 @@ set TASMTABS=%TOOLS%\tasm32
 set CPMDIR80=%TOOLS%/cpm/
 
 zxcc M80 -=zcpr/l || exit /b
-zxcc L80 -zcpr,zcpr.bin/n/e || exit /b
+zxcc L80 -zcpr,zcpr.bin/n/e || exit /b
+
+zxcc M80 -=zcprdemo/l || exit /b
+zxcc L80 -zcprdemo,zcprdemo/n/e || exit /b

Source/ZCPR-DJ/Clean.cmd

@@ -5,3 +5,4 @@ if exist *.bin del *.bin
 if exist *.lst del *.lst
 if exist *.rel del *.rel
 if exist *.prn del *.prn
+if exist *.com del *.com

Source/ZCPR-DJ/zcpr.mac

@@ -1,4 +1,4 @@
-;   DATE 05/17/21 08:34:00
+;   DATE 06/02/21 08:08:00
 ;
 ;	TITLE	ZCPR Console Command Processor - Version D&J
 ;	SUBTTL	Last Modified: 10 August 1997
@@ -396,12 +396,15 @@ CIBUFF:	DB	'             '	;DEFAULT (COLD BOOT) COMMAND 	 13
 	db	0,0,0,0,0,0,0,0	;77
 	db	0,0,0,0,0,0,0,0	;85
 	db	0,0,0,0,0,0,0,0	;93
-	db	0,0,0,0,0,0,0,0	;101
-	db	0,0,0,0,0,0,0,0	;109
+	db	0,0,0		;96
+;	DEFB	0,0,0,0,0,0,0,0	;101
+;	DEFB	0,0,0	;104
+;	DEFB	0,0,0,0,0,0,0,0	;109
+;	DEFB	0,0,0,0,0,0,0,0 ;118
 BUFEND	EQU	$
 ;	DEFW	0		;SENTINEL FOR STACK END
 	db	0,0
-;	DEFS	24		;STACK AREA
+	DEFS	24,0		;STACK AREA
 STACK	EQU	$		;TOP OF STACK
 ;
 ; SUBMIT FILE CONTROL BLOCK
@@ -427,7 +430,7 @@ FCBS2:	db	0		;S2
 FCBRC:	db	0		;RECORD COUNT
 FCBDM:	db	0,0,0,0,0,0,0,0	;DISK GROUP MAP
 	db	0,0,0,0,0,0,0,0
-FCBCR:	DEFS	1		;CURRENT RECORD NUMBER
+FCBCR:	db	0		;CURRENT RECORD NUMBER
 ;
 ; Type and List Variables
 ;
@@ -466,7 +469,7 @@ CMDTBL:
 	DEFW	RING
 	DC	'CLS'
 	DEFW	CLS
-	DC	'WAIT'	; was 'SAK' ("strike any key")
+	DC	'SAK'	; "Strike Any Key"
 	DEFW	SAK
 	DC	'GO'
 	DEFW	GO

Source/ZCPR-DJ/zcprdemo.mac

@@ -1,6 +1,8 @@
-	TITLE	ZCPR Console Command Processor - Version D&J
-	SUBTTL	Last Modified: 5 March 1994
+;   DATE 06/02/21 08:08:00
 ;
+;	TITLE	ZCPR Console Command Processor - Version D&J
+;	SUBTTL	Last Modified: 10 August 1997
+
 ;  CP/M Z80 Command Processor Replacement (CPR) Version 1.0
 ;	CCPZ CREATED AND CUSTOMIZED FOR ARIES-II BY RLC
 ;	FURTHER MODIFIED BY RGF AS V2.0
@@ -66,6 +68,13 @@
 ;
 ; Added PEEK 30 August 1993.
 ;
+; Added CLS 10 August 1997 and fixed two bugs.	One caused the system to
+; hang if the command to log into another drive was given while logged
+; into a drive from which the disk had been removed.  The other caused
+; a warm boot to return to the prior user area if the new user number
+; had been selected using the USER command (although not if the user area
+; had been changed using the du: command).
+;
 ;******** Structure Notes ********
 ;
 ;	This CPR is divided into a number of major sections. The following
@@ -86,39 +95,40 @@
 ;
 ;    3		Utilities
 ;			CRLF	PRINTC	PRINT	PRINTS	BELL
-;			CONOUT	BREAK	CHKETX	ABORT	READF
-;			READ	WRITE	DEFDMA	DMASET	SEARF
-;			SEARDE	SEARN	OPENF	OPEN	CLOSE
-;			CREATE	BDOSFN	SUBKIL	DELETE	TLOGIN
-;			DLOGIN	LOGIN	NEWUSR	RSTUSR	SETUSR
-;			BDOSEA	BDOSJP	BDOSBC	BDOSDE
+;			CLS	CONOUT	BREAK	CHKETX	ABORT
+;			READF	READ	WRITE	DEFDMA	DMASET
+;			SEARF	SEARDE	SEARN	OPENF	OPEN
+;			CLOSE	CREATE	BDOSFN	SUBKIL	DELETE
+;			TLOGIN	DLOGIN	LOGIN	NEWUSR	RSTUSR
+;			SETUSR	BDOSEA	BDOSJP	BDOSBC	BDOSDE
 ;
 ;     4 	CPR Utilities
 ;			PROMPT	REDBUF	CNVBUF	UCASE	SDELM
 ;			ADVAN	SBLANK	ADDAH	NUMBER	A2NUM
 ;			HEXNUM	USRNUM	ERROR	DIRPTR	ULOGIN
-;			SCANER	SCANT	SCANF	CMDSER	SETUDB
+;			SCANER	SCANT	SCANF	CMDSER
 ;
 ;     5 	CPR-Resident Commands and Functions
 ;     5A		DIR	DIRPR	PRFN
 ;     5B		ERA
 ;     5C		ERAQ	PRNNF
 ;     5D		SAK	REPLY
-;     5E		BELL
-;     5F		LIST
-;     5G		TYPE	PAGER
-;     5H		EJECT	
-;     5I		SAVE
-;     5J	 	REN
-;     5K		USER	SUSER
-;     5L		DFU
-;     5M		SCL
-;     5N		PEEK
-;     5O		POKE	
-;     5P		JUMP
-;     5Q		COM
-;     5R		GO 	CLLPRG	ERRLOG	ERRJMP
-;     5S		GET	MEMLD	PRNLE
+;     5E		CLS
+;     5F		BELL
+;     5G		LIST
+;     5H		TYPE	PAGER
+;     5I		EJECT	
+;     5J		SAVE
+;     5K		REN
+;     5L		USER	SUSER
+;     5M		DFU
+;     5N		SCL
+;     5O		PEEK
+;     5P		POKE	
+;     5Q		JUMP
+;     5R		COM	UPDATE
+;     5S		GO	CLLPRG	ERRLOG	ERRJMP
+;     5T		GET	MEMLD	PRNLE
 ;     BIOS		BOOT
 ;
 ;
@@ -142,13 +152,14 @@ TRUE	EQU	NOT FALSE
 ;
 ;  P2DOS  - Address of BDOS/P2DOS.
 ;
-TEST	EQU	FALSE	 	;SET TO LOAD/RUN AT 8000H FOR DEBUG
+TEST	EQU	TRUE	 	;SET TO LOAD/RUN AT 8000H FOR DEBUG
 COMLD	EQU	FALSE		;SET TO LOAD AND EXECUTE AS A .COM FILE
 REL	EQU	FALSE		;SET TO TRUE FOR MOVCPM INTEGRATION
 				;LEAVE ALL FALSE FOR SYSGEN IMAGE
 ;
 BASE	EQU	0		;BASE OF CP/M SYSTEM
-P2DOS	EQU	0E400H		;BASE OF BDOS/P2DOS
+;P2DOS	EQU	0E400H		;BASE OF BDOS/P2DOS (original)
+P2DOS	EQU	0D800H		;BASE OF BDOS/P2DOS (Retro-Brew)
 ZCPRSZ	EQU	00800H		;SIZE OF ZCPR
 P2DOSSZ	EQU	00E00H		;SIZE OF P2DOS	
 BIOS	EQU	P2DOS+P2DOSSZ	;BASE OF BIOS
@@ -243,7 +254,7 @@ SOFLG	EQU	'S'		;LIST $SYS ONLY
 ;
 ; List and Type command customization equates
 ;
-NLINES	EQU	20		;NUMBER OF LINES ON CRT PAGE
+NLINES	EQU	22		;NUMBER OF LINES ON CRT PAGE
 NLINEP	EQU	60		;NUMBER OF LINES ON LIST DEVICE
 FFKILL	EQU	TRUE		;TRUE SUPPRESSES FF UNTIL FIRST CHARACTER
 PGDFLG	EQU	'P'		;TYPE AND LIST COMMAND DEFAULT TOGGLE
@@ -254,14 +265,17 @@ NOSTAT	EQU	FALSE		;SET TO TRUE IF BIOS LISTST NOT IMPLEMENTED
 BUFLEN	EQU	80		;SIZE OF COMMAND INPUT BUFFER 
 MAXUSR	EQU	15		;MAXIMUM USER NUMBER ACCESSIBLE
 DEFUSR	EQU	0		;DEFAULT USER NUMBER FOR COM FILES
+DEFDRV	EQU	'A'		;DEFAULT DRIVE FOR COM FILES
 SPRMPT	EQU	'$'		;CPR PROMPT INDICATING SUBMIT COMMAND
-COMCHR	EQU	';'		;BEGIN COMMENT CHARACTER
+COMCHR	EQU	'%'		;BEGIN COMMENT CHARACTER
 CMDCHR	EQU	';'		;BEGIN NEXT COMMAND CHARACTER
 NUMBASE	EQU	'H'		;CHARACTER USED TO SPECIFY HEXIDECIMAL BASE
 RECFLG	EQU	'R'		;CHARACTER FOR SAVE COMMAND TO SAVE RECORDS
 SUPRES	EQU	TRUE		;TRUE TO SUPPRESS USER NUMBER FOR USER 0
 MULTPL	EQU	TRUE		;TRUE TO ALLOW MULTIPLE COMMANDS ON ONE LINE
 REBOOT	EQU	TRUE		;TRUE TO INCLUDE BOOT COMMAND
+CLSCHR	EQU	1AH		;CHARACTER TO CLEAR TERMINAL SCREEN
+ESC	EQU	1BH		;VT100 LEAD-IN CHAR. (FOR 'CLS')
 ;
 	IF	TEST
 CPRMPT	EQU	'<'		;CPR PROMPT INDICATING TEST MODE
@@ -299,7 +313,7 @@ TPA	EQU	BASE+0100H	;BASE OF TPA
 	IF	COMLD OR TEST
 	LD	HL,BGNXFR
 	LD	DE,CPRLOC
-	LD	BC,ENDLD-CPRLOC
+	LD	BC,ENDLD-BGNXFR
 	LDIR
 	LD	BC,(UDFLAG)
 	JP	CPRLOC
@@ -368,15 +382,29 @@ ENTRY:
 ; warm boot reloads ZCPR and destroys the contents of the command buffer.
 ; The multiple command feature may be turned off with the SCL command.
 ;
-MBUFF:	DEFB	BUFLEN		;MAXIMUM BUFFER LENGTH
+;MBUFF:	DEFB	BUFLEN		;MAXIMUM BUFFER LENGTH
+MBUFF:	DEFB	BUFEND-CIBUFF	;MAXIMUM BUFFER LENGTH
 CBUFF:	DEFB	0		;NUMBER OF CHARACTERS IN COMMAND LINE
-CIBUFF:	DEFB	'             '	;DEFAULT (COLD BOOT) COMMAND
-	DEFB	0		;COMMAND STRING TERMINATOR
-	DEFB	'  ZCPR-D&J of 5 March 1994  '
-	DEFB	0		;TERMINATOR FOR DUMP IDENTIFICATION
-	DEFS	BUFLEN-($-CIBUFF)+1
-	DEFW	0		;SENTINEL FOR STACK END
-	DEFS	24		;STACK AREA
+CIBUFF:	DB	'             '	;DEFAULT (COLD BOOT) COMMAND 	 13
+	DEFB	0		;COMMAND STRING TERMINATOR   	 14
+	DEFB	'  ZCPR-D&J of 17 May 2021     '		;44
+	DEFB	0		;TERMINATOR FOR DUMP IDENTIFICATION  45
+;	DEFS	BUFLEN-($-CIBUFF)+1
+	db	0,0,0,0,0,0,0,0	;53
+	db	0,0,0,0,0,0,0,0	;61
+	db	0,0,0,0,0,0,0,0	;69
+	db	0,0,0,0,0,0,0,0	;77
+	db	0,0,0,0,0,0,0,0	;85
+	db	0,0,0,0,0,0,0,0	;93
+	db	0,0,0		;96
+;	DEFB	0,0,0,0,0,0,0,0	;101
+;	DEFB	0,0,0	;104
+;	DEFB	0,0,0,0,0,0,0,0	;109
+;	DEFB	0,0,0,0,0,0,0,0 ;118
+BUFEND	EQU	$
+;	DEFW	0		;SENTINEL FOR STACK END
+	db	0,0
+	DEFS	24,0		;STACK AREA
 STACK	EQU	$		;TOP OF STACK
 ;
 ; SUBMIT FILE CONTROL BLOCK
@@ -393,22 +421,23 @@ SUBCR	EQU	SUBDN+32	;CURRENT RECORD NUMBER
 ;
 ; COMMAND FILE CONTROL BLOCK
 ;
-FCBDN:	DEFS	1		;DISK DRIVE
-FCBFN:	DEFS	8		;FILE NAME
-FCBFT:	DEFS	3		;FILE TYPE
-FCBEX:	DEFS	1		;EXTENT NUMBER
-FCBS1:	DEFS	1		;S1
-FCBS2:	DEFS	1		;S2
-FCBRC:	DEFS	1		;RECORD COUNT
-FCBDM:	DEFS	16		;DISK GROUP MAP
-FCBCR:	DEFS	1		;CURRENT RECORD NUMBER
+FCBDN:	db	0		;DISK DRIVE
+FCBFN:	db	0,0,0,0,0,0,0,0	;FILE NAME
+FCBFT:	db	0,0,0		;FILE TYPE
+FCBEX:	db	0		;EXTENT NUMBER
+FCBS1:	db	0		;S1
+FCBS2:	db	0		;S2
+FCBRC:	db	0		;RECORD COUNT
+FCBDM:	db	0,0,0,0,0,0,0,0	;DISK GROUP MAP
+	db	0,0,0,0,0,0,0,0
+FCBCR:	db	0		;CURRENT RECORD NUMBER
 ;
 ; Type and List Variables
 ;
-CHRCNT:	DEFS	1		;CHARACTER COUNT FOR TYPE AND LIST
-LNCNT:	DEFS	1		;LINE COUNT FOR TYPE AND LIST
-TYPLST:	DEFS	1		;FLAG FOR TYPE OR LIST
-TABCNT:	DEFS	1		;TAB COUNT FOR TYPE AND LIST
+CHRCNT: db	0		;CHARACTER COUNT FOR TYPE AND LIST
+LNCNT:	db	0		;LINE COUNT FOR TYPE AND LIST
+TYPLST: db	0		;FLAG FOR TYPE OR LIST
+TABCNT: db	0		;TAB COUNT FOR TYPE AND LIST
 SYSTST:	DEFB	0		;LIST SYSTEM FILES IN DIRECTORY FLAG
 ;
 ; General Variables
@@ -416,7 +445,7 @@ SYSTST:	DEFB	0		;LIST SYSTEM FILES IN DIRECTORY FLAG
 CIBPTR:	DEFW	CIBUFF		;POINTER TO COMMAND INPUT BUFFER
 CIPTR:	DEFW	CIBUFF		;POINTER TO CURRENT CMD FOR ERROR REPORTING
 TMPUSR:	DEFB	0		;TEMPORARY USER NUMBER
-TDRIVE:	DEFB	0		;DEFAULT DRIVE
+TDRIVE:	DEFB	0		;TEMPORARY DRIVE
 DFUSR:	DEFB	DEFUSR		;DEFAULT USER
 LDADR:	DEFW	TPA		;MEMORY LOAD ADDRESS
 ;
@@ -434,11 +463,13 @@ CMDTBL:
 	DEFW	USER
 	DC	'DFU'
 	DEFW	DFU
-	DC	'PAGE'
+	DC	'FF'	; was 'PAGE'
 	DEFW	EJECT
 	DC	'BELL'
 	DEFW	RING
-	DC	'SAK'
+	DC	'CLS'
+	DEFW	CLS
+	DC	'SAK'	; "Strike Any Key"
 	DEFW	SAK
 	DC	'GO'
 	DEFW	GO
@@ -458,7 +489,7 @@ CMDTBL:
 	DEFW	PEEK
 	DC	'POKE'
 	DEFW	POKE
-NCMNDS	DEFL	17		;NUMBER OF COMMANDS
+NCMNDS	DEFL	18		;NUMBER OF COMMANDS
 ;
 	IF	MULTPL
 	DC	'SCL'
@@ -515,14 +546,11 @@ RS3:
 	JR	Z,RESTRT	;YES, SKIP REST OF LINE
 	CALL	SCANER		;PARSE COMMAND NAME FROM COMMAND LINE
 	JR	NZ,RS4		;ERROR IF NAME CONTAINS A "?"
-	CALL	DEFDMA		;SET TBUFF TO DMA ADDRESS
-	CALL	DLOGIN		;ASSURE PROPER DRIVE
-	CALL	RSTUSR		;ASSURE PROPER USER NUMBER
-	CALL	SETUDB		;SET UD BYTE TO MATCH USER/DRIVE
-	CALL	CMDSER		;SCAN FOR CPR-RESIDENT COMMAND
+	CALL	CMDSER		;SCAN FOR COMMAND
 ;
 ; ENTRY POINT FOR CONTINUED SCAN OF COMMAND LINE
 ;
+	CALL	UPDATE		;UPDATE BDOS/SYSTEM PARAMETERS
 	CALL	ADVAN		;GET ANY CHARACTER
 	JR	Z,RESTRT	;NONE, END OF LINE
 	LD	(CIPTR),DE	;UPDATE START OF LINE IN CASE ERROR
@@ -1023,7 +1051,7 @@ SCAN4:
 	LD	(HL),B		;SAVE DRIVE
 	LD	B,8	 	;MAX OF 8 CHARACTERS
 	XOR	A		;CLEAR '?' COUNT
-	EX	AF,AF		;AND SAVE
+	EX	AF,AF'		;AND SAVE
 	CALL	SCANF		;GET POSSIBLE NAME
 	CALL	SCANT		;AND POSSIBLE TYPE
 ;
@@ -1043,7 +1071,7 @@ SCAN4:
 ; SCAN COMPLETE -- DE POINTS TO DELIMITER BYTE AFTER TOKEN
 ;
 	LD	(CIBPTR),DE
-	EX	AF,AF		;GET NUMBER OF '?' IN FILENAME.TYP
+	EX	AF,AF'		;GET NUMBER OF '?' IN FILENAME.TYP
 	RET	
 ;
 ; EXTRACT FILE TYPE FROM POSSIBLE FILENAME.TYP
@@ -1068,9 +1096,9 @@ SCAN12:
 SCAN13:
 	CP	'?'		;QUESTION MARK?
 	JR	NZ,SCAN14	;NO, JUST STORE CHARACTER
-	EX	AF,AF		;GET QUESTION MARK COUNT
+	EX	AF,AF'		;GET QUESTION MARK COUNT
 	INC	A		;COUNT IT
-	EX	AF,AF		;AND SAVE COUNT
+	EX	AF,AF'		;AND SAVE COUNT
 SCAN14:
 	INC	DE		;POINT TO NEXT CHARACTER IN COMMAND LINE
 	LD	(HL),A		;STORE CHARACTER IN FCBDN
@@ -1096,15 +1124,6 @@ CMDSER:
 	LD	A,(HL)	 	;LOOK FOR DRIVE SPEC
 	DEC	A		;ADJUST FOR LOG IN
 	CALL	P,TLOGIN	;LOG IN DRIVE
-SETUDB:
-	LD	A,(TMPUSR)	;GET CURRENT USER NUMBER
-	ADD	A,A		;PLACE IT IN HIGH NIBBLE
-	ADD	A,A
-	ADD	A,A
-	ADD	A,A
-	LD	HL,TDRIVE	;ADD DEFAULT DRIVE NUMBER (LOW NIBBLE)
-	OR	(HL)
-	LD	(UDFLAG),A	;UPDATE USER/DRIVE BYTE
 	RET
 CMS0:
 	OR	(HL)		;DRIVE OR USER NUMBER
@@ -1124,11 +1143,10 @@ CMS2:
 	LD	A,(DE)		;NEXT CHARACTER IN INPUT COMMAND MUST BE <SP>
 	CP	' '
 	JR	NZ,CMS4
-	LD	A,(HL)		;FOUND COMMAND,
+	LD	E,(HL)		;FOUND COMMAND,
 	INC	HL		;LOAD ADDRESS,
-	LD	H,(HL)		;AND
-	LD	L,A		;JUMP TO IT
-	JP	(HL)		;COMMAND IS CPR-RESIDENT
+	LD	D,(HL)		;AND
+	JR	CMS6		;UPDATE SYSTEM DATA AND EXECUTE
 CMS3:
 	BIT	7,(HL)		;END OF TABLE ENTRY?
 	INC	HL
@@ -1138,7 +1156,10 @@ CMS4:
 	INC	HL
 	DJNZ	CMS1		;NOT TO END OF TABLE YET
 CMS5:
-	JP	COM		;COMMAND MAY BE DISK-RESIDENT
+	LD	DE,COM		;LOAD DESTINATION AND UPDATE
+CMS6:
+	PUSH	DE		;PLACE ROUTINE ADDRESS ON STACK
+	JP	UPDATE		;UPDATE SYSTEM DATA AND EXECUTE
 ;
 ;**** Section 5 ****
 ; CPR-Resident Commands
@@ -1410,6 +1431,21 @@ REPL2:
 	RET	
 ;
 ;Section 5E
+;Command: CLS
+;Function: To clear screen.
+;Forms:
+;	CLS
+;
+CLS:
+;	LD	A,CLSCHR	; Load clear screen character
+;	DEFB	21H		; and skip next instruction
+				; If a multi-character string is
+				; required to clear screen use:
+	CALL	PRINT
+	DB	ESC,'[2','J'+128
+	RET
+;
+;Section 5F
 ;Command: BELL
 ;Function: To ring terminal bell.
 ;Forms:
@@ -1419,7 +1455,7 @@ RING:
 	LD	A,BELL		; load bell into A
 	JP	CONOUT		; and output it
 ;
-;Section 5F
+;Section 5G
 ;Command: LIST
 ;Function: To print specified file on list device.
 ;Forms:
@@ -1436,7 +1472,7 @@ LIST:
 ;
 	JR	TYPE1
 ;
-;Section 5G
+;Section 5H
 ;Command: TYPE
 ;Function: To display specified file on console.
 ;Forms:
@@ -1559,8 +1595,8 @@ PAGER:
 PAGE2:
 	JP	BDOSJP		; return via bdos
 ;
-;Section 5H
-;Command: PAGE
+;Section 5I
+;Command: FF		(was PAGE)
 ;Function: To eject a page on list device via a form feed.
 ;Forms:
 ;	PAGE
@@ -1578,7 +1614,7 @@ EJECT:
 	LD	C,05H		; list output
 	JP	BDOS		; output character and return via bdos
 ;
-;Section 5I
+;Section 5J
 ;Command: SAVE
 ;Function: To save the contents of TPA onto disk as a file. Number of
 ;	     pages or records is in decimal. Saved area begins at 100H.
@@ -1627,7 +1663,7 @@ SAVE3:
 SAVE4:
 	JP	PRNLE		;PRINT 'NO SPACE' ERROR
 ;
-;Section 5J
+;Section 5K
 ;Command: REN
 ;Function: To change the name of an existing file.
 ;Forms:
@@ -1669,7 +1705,7 @@ NAMERR:
 REN2:
 	JP	ABORT
 ;
-;Section 5K
+;Section 5L
 ;Command: USER
 ;Function: To change current user number; new user number is in decimal.
 ;Forms:
@@ -1679,7 +1715,7 @@ USER:
 	CALL	USRNUM		;EXTRACT USER NUMBER FROM COMMAND LINE
 	JP	NEWUSR		;SET NEW USER NUMBER
 ;
-;Section 5L
+;Section 5M
 ;Command: DFU
 ;Function: To set the Default User Number for the command/file scanner; new
 ;	     default user number is in decimal.
@@ -1691,7 +1727,7 @@ DFU:
 	LD	(DFUSR),A	;PUT IT AWAY
 	RET
 ;
-;Section 5M
+;Section 5N
 ;Command: SCL
 ;Function: To force ZCPR to parse only a single command per line; reset
 ;	     to multiple command format at the next ^C.
@@ -1708,7 +1744,7 @@ SINGLE:
 	ENDIF
 ;
 ;
-;Section 5N
+;Section 5O
 ;Command: PEEK
 ;Function: To display hex values beginning at a specified address.
 ;Forms:
@@ -1755,7 +1791,7 @@ PRHEX:
 	JP	CONOUT		; go display value
 ;
 ;
-;Section 5O
+;Section 5P
 ;Command: POKE
 ;Function: To poke a string of hex values into a set of consecutive addresses.
 ;Forms:
@@ -1776,7 +1812,7 @@ POKE1:
 	JR	POKE1		; go for more
 ;
 ;
-;Section 5P
+;Section 5Q
 ;Command: JUMP
 ;Function: To call the program (subroutine) at the specified address
 ;	     without loading from disk.
@@ -1787,7 +1823,7 @@ JUMP:
 	CALL	HEXNUM		;GET LOAD ADDRESS IN HL
 	JR	CLLPRG		;PERFORM CALL
 ;
-;Section 5Q
+;Section 5R
 ;Command: COM file processing
 ;Function: To load the specified COM file from disk and execute it.
 ;Forms:
@@ -1807,7 +1843,7 @@ COM:
 	CALL	MEMLD		;LOAD MEMORY WITH FILE SPECIFIED
 			 	;(NO RETURN IF ERROR OR TOO BIG)
 ;
-;Section 5R
+;Section 5S
 ;Command: GO
 ;Function: To call the program in the TPA without loading from disk.
 ;	     Same as JUMP 100H, but more convenient, especially when
@@ -1868,14 +1904,24 @@ COM3:
 ; RUN LOADED TRANSIENT PROGRAM
 ;
 	CALL	CRLF		;NEW LINE
-	CALL	DEFDMA		;SET DMA TO 0080
-	CALL	RSTUSR		;RESET TO PROPER USER NUMBER
+UPDATE:
+	CALL	DEFDMA		;SET DMA TO DEFAULT VALUE
+	CALL	DLOGIN		;ASSURE PROPER DRIVE
+	CALL	RSTUSR		;ASSURE PROPER USER NUMBER
+	LD	A,E		;GET CURRENT USER NUMBER
+	ADD	A,A		;PLACE IT IN HIGH NIBBLE
+	ADD	A,A
+	ADD	A,A
+	ADD	A,A
+	LD	HL,TDRIVE	;ADD DEFAULT DRIVE NUMBER (LOW NIBBLE)
+	OR	(HL)
+	LD	(UDFLAG),A	;UPDATE USER/DRIVE BYTE
 ;
-; EXECUTION (CALL) OF PROGRAM (SUBROUTINE) OCCURS HERE
+; EXECUTION (CALL) OF PROGRAM/SUBROUTINE/COMMAND OCCURS HERE
 ;
 	RET			;CALL TRANSIENT
 ;
-;Section 5S
+;Section 5T
 ;Command: GET
 ;Function: To load the specified file from disk to the specified address
 ;Forms:
@@ -1896,9 +1942,9 @@ MEMLD:
 	LD	(LDADR),HL	;SET LOAD ADDRESS
 ;
 ;   MLA is a reentry point for a non-standard CP/M Modification
-; This is the return point when the .COM (or GET) file is not found the
-; first time, the Default User is selected for the second attempt
-; and Drive A is selected for the final attempt.
+; This is the return point when the .COM (or GET) file was not found 
+; so the Default Drive & User are selected for the final attempt
+; to find the file.
 ;
 MLA:
 	CALL	ULOGIN		;LOG ANY USER
@@ -1906,29 +1952,22 @@ MLA:
 	CALL	OPENF		;OPEN COMMAND.COM FILE
 	JR	NZ,MLA1		;FILE FOUND - LOAD IT
 ;
-; FILE NOT FOUND - SELECT DEFAULT USER
+; FILE NOT FOUND - SELECT DEFAULT COM USER
 ;
-	LD	A,L	 	;GET FCB USER
-	AND	A		;DEFAULT USER?
-	JR	NZ,MLA0		;NO
-	LD	HL,TMPUSR	;CURRENT USER SAME AS DEFAULT?
 	LD	A,(DFUSR)	;GET DEFAULT USER
-	CP	(HL)
 	SET	7,A		;MAKE INTO VALID USER NUMBER
 	LD	(FCBS1),A	;PUT USER INTO FCB
-	JR	NZ,MLA		;AND TRY AGAIN
 ;
-; FILE NOT FOUND - SELECT DRIVE A IF DEFAULT WAS SOME OTHER DRIVE
+; AND SELECT DEFAULT COM DRIVE.  IF DEFAULT COM DRIVE ALREADY
+; SELECTED, GIVE UP AND PRINT ERROR MESSAGE
 ;
 MLA0:
-	LD	A,(TDRIVE)	;DRIVE A DEFAULT?
-	AND	A
+	LD	A,DEFDRV-'@'	;A<= DEFAULT COM DRIVE 
+	LD	HL,FCBDN	;POINT TO DRIVE IN FCB
+	CP	(HL)		;THE SAME?
 	JR	Z,MLA3	 	;YES, ERROR
-	XOR	A
-	LD	HL,FCBDN	;POINT AT DRIVE IN FCB
-	OR	(HL)		;DRIVE ALREADY SPECIFIED?
-	LD	(HL),1		;SELECT DRIVE A
-	JR	Z,MLA		;NO, GO GIVE IT A TRY
+	LD	(HL),A		;PUT DEFAULT COM DRIVE IN FCB
+	JR	MLA		;GO GIVE IT A TRY
 MLA3:
 	CALL	PRNNF		;CAN'T FIND FILE
 	JR	PRNLE1
@@ -1961,6 +2000,7 @@ PRNLE1:
 	IF	(($-ENTRY) GT ZCPRSZ)
 	*ZCPR too large!!*
 	ENDIF
+	.DEPHASE
 ;
 	IF	TEST
 LISTST:
@@ -1977,4 +2017,4 @@ ENDLD	EQU	$
 
 	END	
 
-	PUSH	HL		;SAVE POI
+