TITLE	NOVA DISPLAYî

	A==0		;ACCUMULATORS
	B==1
	C==2
	D==3

	RTC==14		;IO DEVICES
	DSPL==41
	PDPI==6
	PDPO==7

	DRANEW==3	;CODE MODE SHIFTED RIGHT
	ACK==6		;PDP10 ERROR ACKNOWLEDGE

	LEN==7000	;DISPLAY AREA LENGTH
	LLEN==2000	;LISTS OF LISTS LENGTH

	LOADER==17000	;ADDRESS OF NOVA BLOCK LOADER (HIGHEST LEGAL ADDR +1)


DEFINE ERROR X
	LDA	A,[X]
	JMP	@CTENER
TERMIN

	LOC	0
		0
CINTRP:		INTRP
CRESET:		RESET
VERS:		.FNAM2_-18.


	LOC	50

TENCOM:		200	;PDP10 COMMAND CODES -- MVTO
		220	;PTAT
		260	;PDWN
		100	;SHIP
		120	;ESHIP
		140	;DST
		160	;DREM
		300	;SHOW
		320	;HIDE
		360	;RESET
		340	;WIPE
		240	;NFRM
FDL:		0	;BADCOM -- USE ALSO AS FAKE DISPLAY LIST
DCOM:		MVTO	;COMMAND SUBROUTINES
		PTAT
		PDWN
		SHIP
		ESHIP
		DST
		DREM
		SHOW
		HIDE
		RESET
CWIPE:		WIPE
		NFRM
CONTIN:		CLOCK
	CCLOCK=CONTIN
TENCT:		3	;MVTO
		10	;PTAT
		2	;PDWN
		2	;SHIP
		1	;ESHIP
		2	;DST
		2	;DREM
		1	;SHOW
		1	;HIDE
		1	;RESET
		1	;WIPE
		1	;NFRM
		1	;BADCOM
GETWD:		BLOCK 10


CFDL:		FDL
CDLT:		DLT
CDLB:		DLB
CLDL:		DLB-DLT+1
CAVAIL:		AVAIL
CROV:		ROV
CTOP:		DLLT
CTOP2:		DLLT-4
CBOT:		DLLB
PO:		0
N:		0
R:		DLLT-4
CBLT:		BLT
CDRAW:		DRAW
CDRAAD:		DRAAD
CDRBM:		DRBM
CFRAM:		FRAM
CREM:		REM
CINST:		INST
COUTQ:		OUTQ
CINQ:		INQ
CPTBUF:		PTBUF	;CPTBUF-1 MUST BE NON-0
CTENER:		TENERR
CGETEN:		GETEN
CSSHIP:		SSHIP
CEESHI:		EESHIP
CDLIM:		DLIM

CTEMP:		0
CTEMP1:		0
STIME:		0
PKPTR:		DLLT-4
GETCT:		0
CPX:		PX
LISTAD:		0
CPQ:		CPQTOP
CDISAD:		CPTBUF-1
DISAD:		CPTBUF-1
DRARET:		0
DRACNT:		0
DRLEN:		0
DRASV:		0
CDROUT:		DROUT
CURX:		0
CURY:		0
XF:		0
YF:		0
XT:		0
YT:		0
HDFLG:		1	;FLAGS
ERRFL:		0
GETFL:		0
SHIPFL:		0
SBMFL:		0
DBMFL:		0
XDIR:		0
YDIR:		0

;INTERRUPT--
;IF PDP-10 INTERRUPTS INSERT WORD IN 10 QUEUE

ITSVA:	0		;ACCUMULATORS AND CARRY SAVED HERE
ITSVB:	0
ITSVC:	0
ITSVD:	0
ITSVCY:	0

INTRP:	STA	A,ITSVA	;SAVE ACCUMULATORS
	STA	B,ITSVB
	STA	C,ITSVC
	STA	D,ITSVD
	MOVL	D,D	;SAVE CARRY
	STA	D,ITSVCY


	SKPDZ	PDPI	;CHECK PDP-10 INPUT
	JMP	ITPDP

	DIBC	A,CPU	;CLEAR "PHANTOM INTERRUPT"
	HALT		;STOP

	JMP	ITRES	;RESTORE WORLD


ITPDP:	DIAS	A,PDPI
	LDA	B,[ACK]
	SUB	A,B(SNR)
	JMP	ITPDP2	;CHAR IS ERROR ACKNOWLEDGE

	LDA	D,ERRFL
	MOV%	D,D(SZR)
	JMP	ITRES	;WAITING FOR 10 TO ACKNOWLEDGE ERROR

	LDA	C,[37]	;MASK FOR ALL BUT DATA BITS
	ANDZR	C,A(SNC)
	JMP	ITPDP1
	ADDZL	A,A	;SHIFT LEFT 4
	ADDZL	A,A
	STA	A,PWORD
	JMP	ITRES
ITPDP1:	LDA	B,PWORD
	ADD	B,A
	JSR	@CINQ
	JMP	ITRES

ITPDP2:	STA	B,ERRFL	;RESET ERROR FLAG
	JMP	ITRES

PWORD:	0	;PDP-10 WORD SAVED HERE

ITRES:	LDA	A,ITSVCY	;RESTORE INTERRUPTS
	MOVR	A,A
	LDA	A,ITSVA	;RESTORE ACCUMULATORS
	LDA	B,ITSVB
	LDA	C,ITSVC
	LDA	D,ITSVD

	INTEN		;ENABLE INTERRUPTS
	JMP	@0	;RETURN TO ADDRESS INTERRUPTED FROM


;RESET--
;RESTART PROGRAM
;RESET POINTERS AND VARIABLES
;WIPE OUT BUFFERS

RESET:	INTDS

	LDA	B,CDLB
	LDA	C,CTOP
	LDA	D,[4]
	SUB	A,A(SKP)	;A/0 (SKIPA)
RSZDL:	ADD D,C
	STA	A,0(C)	;ZERO DLLT THRU DLB
	STA	A,1(C)
	SUBZ%	B,C(SNC)
	JMP	RSZDL

	LDA	D,CDLT	;FIX DL
	LDA	C,CLDL
	STA	C,0(D)
	STA	A,1(D)

	LDA	C,CROV	;FIX AVAIL AND ROV
	STA	A,0(C)
	STA	A,1(C)
	LDA	C,CAVAIL
	STA	A,0(C)
	STA	D,1(C)
RSZCN:	IRPS	X,,[STIME SBMFL DBMFL SHIPFL CURX CURY
GETFL PO N 20 DRASV XDIR YDIR]
	STA	A,X
	TERMIN

	LDA	C,CPX
	IRPS	X,,0 1 2 3 4 5
	STA	A,X(C)
	TERMIN

	LDA	A,CTOP2
	STA	A,PKPTR
	STA	A,R


	SUBZL	A,A
	STA	A,HDFLG
	LDA	A,[2]
	STA	A,@CPTBUF
	LDA	A,CDISAD
	STA	A,DISAD
	LDA	C,CPQ
	LDA	A,0(C)
	STA	A,1(C)
	STA	A,2(C)

;FALLS THROUGH


;FALLS IN

RSIO:	IORST		;RESET IO DEVICES
	LDA	A,[176777]	;MASK OUT ALL BUT PDPI (AND CPU)
	MSKO	A,
	NIOS	PDPI	;PDP10 INPUT
	NIOC	PDPO	;PDP10 OUTPUT
	LDA	D,CFDL
	ADC	A,A
	DOB	D,DSPL	;FAKE DISPLAY LIST (NULL WORD)
	DOCS	A,DSPL	;LENGTH=1

	INTEN

	JMP	@CGETEN


;DISPLAY OUT--
;GET NEXT ACTIVE DISPLAY LIST FROM DISAD
;GIVE ADDRESS OF START OF DISPLAY INSTRUCTIONS
;AND LENGTH OF DISPLAY INSTRUCTIONS TO DISPLAY

DSO:	SKPBZ	DSPL
	JMP	.-1	;DISPLAY STILL BUSY
	LDA	C,DISAD
	MOV%	C,C(SNR)
	JMP	DSO2	;NOTHING TO DISPLAY
	LDA	D,1(C)	;ADDR OF LOAD DISPLAY LIST
	LDA	A,0(D)	;LOAD LENGTH OF DISPL LIST
	NEG	A,A
	INC	A,A	;-(LENGTH-1)
	INC	D,D	;START OF DISP INSTRUCTIONS
	MOVL%	A,A(SNC)
	JMP	DSO3
	DOB	D,DSPL	;ADDRESS TO B BUFFER
	DOCS	A,DSPL	;LENGTH TO C BUFFER

DSO2:	JMP	@CGETEN
 
DSO3:	HALT			;TRAP FOR POSITIVE LENGTH

;FALLS THROUGH

;FALLS IN

;GET 10--
;TRY TO READ PDP10 CODES FROM QUEUE
;JUMP TO APPROPRIATE SUBROUTINE WHEN
;CODE IS RECOGNIZED

GETEN:	LDA	A,GETFL
	MOV%	A,A(SZR)	;READY TO READ CODE?
	JMP	GETEN6	;NO
	JSR	@COUTQ	;TRY TO READ CODE
	JMP	@CCLOCK	;FAIL
	STA	A,GETWD	;SUCCEED
	LDA	C,[360]	;MASK ALL BUT CODE BITS
	AND	C,A
	SUB	C,C(SKP)	;IDENTIFY CODE (SKIPA)

GETEN1:	INC	C,C
	LDA	B,TENCOM(C)
	MOV	B,B(SNR)	;0=ERROR CANT IDENTIFY
	JMP	GETEN2
	SUB%	A,B(SZR)
	JMP	GETEN1

GETEN2:	STA	C,GETC	;FOUND CODE
	LDA	A,TENCT(C)	;NUMBER OF WORDS TO READ
	STA	A,GETCT
	DSZ	GETCT
	JMP	GETEN4
GETEN3:	SUB	B,B	;ALL WORDS READ
	STA	B,GETFL
	LDA	C,GETC
	JMP	@DCOM(C)
GETEN4:	SUBZL	C,C
GETEN5:	STA	C,GETC1	;NUMBER OF WORDS READ
GETEN6:	JSR	@COUTQ	;TRY TO READ NEXT WORD
	JMP	GETEN7	;FAIL
	LDA	C,GETC1
	STA	A,+GETWD(C)
	INC	C,C
	LDA	A,GETCT
	ADCZ%	A,C(SNC)	;GETC1>GETCT?
	JMP	GETEN5	;NO--READ NEXT
	JMP	GETEN3	;YES--ALL READ
GETEN7:	SUBZL	B,B
	STA	B,GETFL	;SET FAIL FLAG AND LEAVE
	JMP	@CCLOCK
GETC:		0
GETC1:		0

;MOVE TO--
;UNPACK COORDINATES, AND IF PEN IS
;DOWN, DRAW LINE AND INSERT IN LIST
;OF LISTS FOR APPROPRIATE TIME

MVTO:	SUB	C,C	;UNPACK XY COORDS
	JSR	NPK1
	LDA	C,[1777]
	AND	C,A
	AND	C,B
	STA	A,XT
	STA	B,YT
	LDA	C,SHIPFL
	MOV%	C,C(SZR)	;ARE WE SHIPPING?
	JMP	MVTO2	;YES

	LDA	C,CURX
	LDA	D,CURY
	STA	A,CURX	;CHANGE CURRENT X,Y
	STA	B,CURY
	STA	C,XF
	STA	D,YF
	LDA	B,STIME
	MOV%	B,B(SNR)	;PENUP?
	JMP	MVTO1

	JSR	@CDRAW	;NO, DRAW LINE
	LDA	A,DRLEN
	LDA	B,CDROUT	;ADDR TO B
	SUB	C,C	;LISTAD SHOULD BE ZERO
	STA	C,LISTAD
	JSR	@CINST	;INSERT IN DISPLAY LIST AREA
MVTO1:	JSR	@CPTUP	;UPDATE POINTER
	JMP	@CONTIN

MVTO2:	JSR	@CDRAAD	;ADD TO LIST
	JMP	@CONTIN

CPTUP:	PTUP


;UNPACK--
;UNPACK COORDINATES FROM TEN FOR MVTO & PTAT

NPK1:	LDA	A,GETWD(C)
	LDA	B,[17]
	AND	B,A
	MOVS	A,A
	LDA	B,GETWD+1(C)
	ADD	B,A
	MOVZR	A,A
	MOVZR	A,A
	STA	A,NPKA
	LDA	A,GETWD+1(C)
	LDA	B,[3]
	AND	B,A
	MOVS	A,A
	LDA	B,GETWD+2(C)
	ADD	A,B
	LDA	A,NPKA
	JMP	0(D)
NPKA:		0
PX:		0
PY:		0
PXP:		0
PYP:		0
PXPP:		0
PYPP:		0


;POINTER AT--
;POINTER LOCATION NAMED BY THREE VERTICES
;UNPACK COORDINATES AND
;COMPILE DISPLAY LIST FOR POINTER

PTAT:	SUB	C,C	;UNPACK X,Y
	JSR	NPK1
	STA	A,PX
	STA	B,PY
	LDA	A,GETWD+3	;UNPACK X',Y'
	MOVZL	A,A
	MOVZL	A,A
	LDA	C,[6]
	STA	C,CTEMP
	LDA	B,GETWD+4
	MOVZR	B,B
	DSZ	CTEMP
	JMP	.-2
	ADD	B,A
	STA	A,PXP
	LDA	A,GETWD+4
	LDA	C,[77]
	AND	C,A
	LDA	B,GETWD+5
	LDA	C,[4]
	STA	C,CTEMP
	MOVZL	A,A
	MOVZR	B,B
	DSZ	CTEMP
	JMP	.-3
	ADD	B,A
	STA	A,PYP
	LDA	C,[5]	;UNPACK X'',Y''
	JSR	NPK1
	STA	A,PXPP
	STA	B,PYPP

;FALLS THROUGH


;FALLS IN

PTATA:	JSR	@CSSHIP	;START APPENDING
	LDA	A,CURX	;DRAW FROM (CURX, CURY)
	LDA	B,CURY
	STA	A,XF
	STA	B,YF
	LDA	A,PXP	;TO (PXP, PYP)
	LDA	B,PYP
	JSR	ADR
	LDA	A,PXPP	;TO (PXPP, PYPP)
	LDA	B,PYPP
	JSR	ADR
	LDA	A,PX	;TO (PX, PY)
	LDA	B,PY
	JSR	ADR
	LDA	A,CURX	;TO (CURX, CURY)
	LDA	B,CURY
	JSR	ADR

PTAT2:	JSR	@CEESHI	;TERMINATE LIST
	LDA	A,DRLEN
	LDA	B,CDROUT
	LDA	C,CPTBUF
	JSR	XFER	;TRANSFER LIST FROM DROUT TO PTBUF

	LDA	A,CURX	;CHANGE XF AND YF TO CURRENT POS
	LDA	B,CURY
	STA	A,XF
	STA	B,YF
	JSR	PTUP1
	JMP	@CONTIN

ADR:	STA	A,XT	;(CALLED WITH JSR)
	STA	B,YT
	JMP	@CDRAAD


;POINTER UP--
;UPDATE POINTER TO (CURX, CURY)

PTUP:	LDA	A,CURX
	LDA	B,CURY
PTUP1:	SUBZR	C,C
	ADD	C,A	;POINT MODE X
	LDA	C,[120000]
	ADD	C,B	;POINT MODE Y
	LDA	C,CPTBUF
	STA	A,2(C)	;STORE AT TOP OF POINTER DISPLAY LIST
	STA	B,3(C)
	JMP	0(D)


;TRANSFER--
;BLT LENGTH A FROM B TO C

XFER:	STA	D,XFERR
	STA	A,.+4
	STA	B,.+4
	STA	C,.+4
	JSR	@CBLT
		0	;LENGTH
		0	;SOURCE ADDRR
		0	;DEST	ADDR
	JSR	@XFERR

XFERR:		0


;BLOCK TRANSFER--
;TRANFER BLOCK 0(D) OF LENGTH 1(D) TO
;2(D)

BLT:	DSZ	1(D)
	LDA	A,1(D)
	STA	A,20
	DSZ	2(D)
	LDA	A,2(D)
	STA	A,21
BLT1:	LDA	A,@20
	STA	A,@21
	DSZ	0(D)
	JMP	BLT1
	JMP	3(D)


;PENDOWN--
;IF TIME NAMED BY 10 IS 7777 MAKE STIME -1 (INFINITY)
;OTHERWISE MAKE STIME TIME NAMED BY PDP10

PDWN:	LDA	C,[17]
	LDA	A,GETWD
	AND	C,A
	MOVS	A,A
	LDA	B,GETWD+1
	ADD	B,A
	LDA	B,[7777]	;N=INFINITY?
	LDA	C,SHIPFL
	MOV%	C,C(SZR)
	JMP	PDWN1

	SUB%	A,B(SNR)
	LDA	A,[-1]
	STA	A,STIME
	JMP	@CONTIN

PDWN1:	SUB%	A,B(SZR)	;PENDOWN?
	SUB	C,C	;YES--(IF PDWN SBMFL=1, ELSE =0)
	STA	C,SBMFL
	JMP	@CONTIN


;HIDE--
;TURN ON HIDE FLAG
;SHOW--
;TURN OFF HIDE FLAG

SHOW:	SUB	A,A(SKP)
HIDE:	SUBZL	A,A
	STA	A,HDFLG
	JMP	@CONTIN


;DISPLAY--
;DISPLAY DISPLAY LIST NAMED BY PDP-10 STARTING AT CURRENT LOCATION
;IN CURRENT PENDOWN MODE

DST:	LDA	A,STIME
	MOV%	A,A(SNR)
	JMP	@CONTIN
	JSR	DLP	;DOES LIST WITH THAT NAME EXIST?
			;YES, AC2 POINTS TO NAME (IF NO, NEVER RETURNS)
	LDA	D,1(C)
	STA	D,LISTAD
	JSR	@CINST	;MOVETO CURRENT DISPLAY LIST AREA
	JMP	@CONTIN

DSTLP:	0		;LENGTH OF SOURCE LIST SAVE HERE


			;THIS SUBROUTINE SEARCHES FOR DISPLAY LIST IN ACTIVE DISPLAY LIST
			;AREA, WITH NAME THAT MATCHES NAME IN PDP-10 COMMAND
DLP:	STA	D,DSTLP	;SAVE RETURN ADDRESS
	LDA	A,GETWD+1	;NAME OF DESIRED LIST
	SUBZR	B,B
	ADD	B,A	;STORED VERSION OF LIST NAME
	LDA	B,CBOT	;ADDRESS OF BOTTOM OF DISPLAY LIST BUFFER
	LDA	C,CTOP	;ADDRESS OF FRAME TIME OR LIST NAME

DLP1:	LDA	D,0(C)	;TIME OR NAME
	SUB%	A,D(SNR)	;IS NAME DESIRED ONE?

	JMP	@DSTLP	;YES, RETURN TO CALLING ROUTINE

	LDA	D,[4]	;CHECK NEXT LIST
	ADD	D,C
	ADCZ%	B,C(SZC)	;HAVE ALL LISTS BEEN CHECKED?
	JMP	@CONTIN	;YES, IGNORE PDP-10 INSTRUCTION
	JMP	DLP1	;NO, CONTINUE SEARCH



;DISPLAY REMOVE--
;REMOVE LIST SHIPPED FROM 10 FROM ACTIVE AREA
;REMOVE ALL REFERENCES TO LIST

DREM:	JSR	DLP	;SEARCH FOR LIST WITH SAME NAME
		;SUCCESS, AC2 IS ADDRESS OF NAME
	SUB	A,A	;0
	STA	A,0(C)	;MAKE FRAMES ZERO

	LDA	D,1(C)	;ADDRESS OF DISPLAY LIST
	STA	D,PO
	STA	D,LISTAD
	LDA	B,0(D)
	STA	B,N
	STA	A,1(C)	;ZERO ADDRESS

	JSR	@CREM	;REMOVES DISPLAY LIST

	LDA	C,CTOP	;REMOVE ALL REFERENCES TO THIS LIST
	LDA	B,CBOT
	LDA	A,LISTAD
DREM3:	LDA	D,1(C)
	SUB%	A,D(SZR)
	JMP	DREM4
	SUB	D,D
	STA	D,0(C)
	STA	D,1(C)
	STA	D,2(C)
	STA	D,3(C)
DREM4:	LDA	D,[4]
	ADD	D,C
	ADCZ%	B,C(SZC)
	JMP	@CONTIN
	JMP	DREM3


;SHIP--
;GET DISPLAY LIST INSTRUCTIONS FROM PDP10
;TURN ON SHIP FLAG
;SAVE NAME OF LIST, INITIALIZE DRAW PARAMETERS

SHIP:	JSR	@CSSHIP	;INITIALIZE DRAAD
	LDA	A,GETWD+1
	STA	A,LISTN	;NAME OF LIST

	LDA	A,CURX	;FIX TEMP X AND Y COORDS
	LDA	B,CURY
	STA	A,XF
	STA	B,YF

	JMP	@CONTIN	;CONTINUE

LISTN:	0

SSHIP:	SUBZL	A,A
	STA	A,SHIPFL	;SHIPFL=1
	STA	A,SBMFL
	SUB	A,A
	STA	A,DBMFL	;DBMFL=0
	STA	A,XDIR
	STA	A,YDIR
	LDA	B,CDROUT
	STA	B,20	;AUTO-INC
	STA	A,@20	;SPACE FOR NULL,X,Y
	STA	A,@20
	STA	A,@20
	LDA	A,[DRANEW]	;CODE MODE
	STA	A,DRASV	;MAKE DRAW THINK THIS IS LAST WORD COMPILED
	JMP	0(D)


;END SHIP--
;TURN OFF SHIP FLAG, STORE COMPILED LIST
;(COMPLEMENT BEAM IF NECESSARY TO LEAVE OFF)


ESHIP:	LDA	A,SHIPFL
	MOV%	A,A(SNR)
	JMP	@CONTIN	;IGNORE IF NOT SHIPPING
	JSR	@CEESHI	;FINISH UP LIST

ESHIP1:	LDA	A,DRLEN	;LENGTH TO A
	LDA	B,CDROUT	;ADDRESS TO B
	LDA	C,LISTN	;NAME

	LDA	D,STIME
	STA	D,LISTN	;SAVE STIME IN LISTN

	SUBZR	D,D
	ADD	D,C	;STORED FORM OF NAME
	STA	C,STIME	;LIST NAME IN STIME

	SUB	C,C	;BE SURE LISTAD IS ZERO
	STA	C,LISTAD

	JSR	@CINST	;INSERT IN DL
	LDA	A,LISTN
	STA	A,STIME	;RESTORE CURRENT TIME
	JMP	@CONTIN

EESHIP:	SUB	A,A
	STA	A,SHIPFL

	LDA	A,DRASV	;LAST WORD COMPILED
	STA	D,DRARET	;DRAW RETURN ADDRESS
	LDA	C,DBMFL	;CURRENT STATE OF BEAM
	MOV%	C,C(SNR)	;COMPLEMENT BEAM?
	JMP	@ENCOMP	;NO
	JMP	@ECOMP	;YES

ENCOMP:	DRATR0	;JUMP HERE IF BEAM ALREADY OFF
ECOMP:	DRATRA	;JUMP HERE TO COMPLEMENT BEAM


;WIPE--
;REMOVES ALL DISPLAY LISTS
;WITH POSITIVE OR INFINITE (-1) TIME LEFT

WIPE:	LDA	C,CTOP2
	LDA	B,CBOT
	SUB	A,A

WIPE1:	LDA	A,[4]
	ADD	A,C
	ADCZ%	B,C(SZC)	;ARE WE AT BOTTOM OF LIST OF LISTS?
	JMP	@CONTIN	;YES

	LDA	A,0(C)	;NO,GET TIME
	MOV%	A,A(SNR)
	JMP	WIPE1
	INCZL%	A,A(SEZ)	;IS TIME -1 OR POSITIVE?
	JMP	WIPE1	;NO,GET NEXT LIST

	SUB	A,A	;YES, WIPE OUT
	STA	A,0(C)	;MAKE TIME ZERO

	LDA	D,3(C)	;CHECK TO SEE IF THIS IS A REFERENCE
	MOV%	D,D(SNR)
	JMP	WIPE2
	STA	A,1(C)	;ZERO OUT REFERENCE
	STA	A,2(C)
	STA	A,3(C)
	JMP	WIPE1

WIPE2:	LDA	D,1(C)
	STA	D,PO	;ARG FOR REM
	LDA	B,0(D)
	STA	B,N
	STA	C,WPTR	;SAVE POINTER
	STA	A,1(C)	;ZERO ADDRESS
	JSR	@CREM	;REMOVE LIST

	LDA	B,CBOT	;RESTORE CBOT
	LDA	C,WPTR	;RESTORE POINTER
	JMP	WIPE1

WPTR:	0
;NEWFRAME--DECREMENT FRAME TIMES AND UPDATE DISPLAY LISTS

NFRM:	JSR	@CFRAM
	JMP	@CONTIN


;CLOCK--
;FIND NEXT ACTIVE LIST ANDJUMP TO DSO

CLOCK:	LDA A,CTOP2
	LDA B,CBOT	;CHECK FOR PKPTR
	LDA C,PKPTR
	JSR @CDLIM

	JSR	DPICK
	SUB	A,A	;FAILî
	STA	A,DISAD	;SUCCEED

	LDA A,CTOP2
	LDA B,CBOT	;CHECK FOR PKPTR
	LDA C,PKPTR
	JSR @CDLIM

	JMP	@CPKR

CPKR:		DSO


;DPICK--
;PICK NEXT ACTIVE DISPLAY LIST

DPICK:	SUB	A,A	;CLEAR FLAGS
	STA	A,DPFLG
DPICK1:	LDA	A,PKPTR
	LDA	B,[4]
	ADD	B,A
	STA	A,PKPTR
	LDA	B,CBOT
	SUBZ%	B,A(SNC)	;A>=B?
	JMP	DPICK2	;NO
	LDA	A,CTOP2
	STA	A,PKPTR
	LDA	B,DPFLG	;FLAG ON?
	MOV%	B,B(SZR)
	JMP	0(D)	;YES
	SUBZL	B,B	;SET FLAG
	STA	B,DPFLG
	LDA	B,HDFLG	;DISPLAY POINTER?
	MOV%	B,B(SZR)
	JMP	DPICK1	;NO
	LDA	A,CDISAD	;SUCCEED
	JMP	1(D)
DPICK2:	MOV	A,C
	LDA	B,0(C)
	MOV%	B,B(SNR)
	JMP	DPICK1
	INCL%	B,B(SZC)
	JMP	DPICK1	;NOT A DISPLAY LIST
	LDA	B,2(C)
	MOV%	B,B(SNR)
	JMP	1(D)
	STA	D,DPFLG	;SET UP REFERENCE
	LDA	D,1(C)
	STA	B,2(D)
	LDA	B,3(C)
	STA	B,3(D)
	LDA	D,DPFLG
	JMP	1(D)	;RETURN TO SUCCESS
DPFLG:		0


;INSERT--
;INSERT BLOCK IN DISPLAY LIST
;THIS SUBROUTINE LOOKS FOR
;EMPTY BLOCKS IN DISPLAY LIST AREA
;WHICH ARE LARGE ENOUGH TO ACCOMODATE
;DISPLAY LIST.
;CALLED WITH THE DISPLAY LIST
;LENGTH IN INLEN, AND THE ADDRESS IN
;INADR

INST:	STA	D,INRET
	STA	A,INLEN	;A CONTAINS LENGTH
	STA	B,INADR	;B CONTAINS ADDRESS
	SUB	B,B	;SWITCH OFF
	LDA	D,CBOT	;ADDR OF FINAL PSTN
	LDA	C,R	;PREVIOUS INSERTION


		;CHECK LIST OF DISPLAY LISTS (CTOP-CBOT)
		;FOR  SOME SPOT WE CAN INSERT THE ADDRESS
		;AND TIME OF THE CURRENT LIST
INST0:	LDA	A,[4]	;FIND NEXT POSITION
	ADD	A,C
	ADCZ%	C,D(SZC)	;IS THIS FINAL PSTN IN LIST OF DISPLAY LISTS?
	JMP	INST1		;NO, SEE IF WE CAN INSERT INFORMATION HERE

	MOV%	B,B(SNR)	;YES--SWITCH ON?
			;HAVE WE BEEEN THROUGH LIST OF LISTS ONCE ALREADY?
	JMP	INST2	;NO, SET SWITCH

	ERROR	1	;TOO MANY LISTS!!!

INST1:	LDA	A,0(C)	;FRAME	TIME
	MOV%	A,A(SNR)	;IS IT ZERO?
	JMP	INST3	;YES, USE THIS LOCATION
	JMP	INST0	;NO, FIND NEXT POSITION

INST2:	INC	B,B	;SET SWITCH
	LDA	C,CTOP	;MOVE BACK TO TOP OF LIST OF LISTS
	JMP	INST1


		;INSERT TIME AND LENGTH IN PROPER
		;SPOT IN LIST OF DISPLAY LISTS
		;ACC C CONTAINS ADDRESS WHERE TIME
		;WILL BE INSERTED
		;FIRST, FIND SECOND FREE BLOCK

INST3:	STA	C,R
	LDA	A,LISTAD
	MOV%	A,A(SNR)
	JMP	INST3A
	LDA	B,CURX	;CREATE REFERENCE
	SUBZR	A,A
	ADD	A,B
	STA	B,2(C)	;X COORDINATE
	MOVZR	A,A
	MOVOR	A,A
	LDA	B,CURY
	ADD	A,B
	STA	B,3(C)	;Y-COORDINATE
	LDA	B,STIME
	STA	B,0(C)
	LDA	B,LISTAD
	STA	B,1(C)	;ADDRESS REFERENCE
	JMP	@INRET


INST3A:	LDA	D,CROV	;ADDR OF ROVING POINTER TO DISPLAY LIST AREA
	SUB	B,B	;PUT SWITCH OFF  (SWITCH WILL NOW BE USED
	STA	B,INSTS	;TO CHECK HOW MANY TIMES WE HAVE GONE
			;OVER DISPLAY LIST AREA)

		;IN DISPLAY AREA, ROV IS POINTER TO
		;FIRST FREE BLOCK.  THE FIRST ADDRESS
		;IN EACH BLOCK CONTAINS THE LENGTH OF THE
		;BLOCK, THE SECOND ADDRESS POINTS TO THE
		;NEXT FREE BLOCK.  THE SECOND ADDRESS
		;OF THE LAST FREE BLOCK CONTAINS ZERO.

;FALLS THROUGH


INST4:	LDA	C,1(D)	;ADDR OF NEXT FREE BLOCK
	MOV%	C,C(SZR)	;END  OF DISPLAY AREA?
	JMP	INST5	;NO, SEE IF BLOCK IS THE RIGHT LENGTH

	LDA	B,INSTS
	MOV%	B,B(SNR)	;YES--SWITCH ALREADY ON?
			;HAVE WE BEEEN THROUGH DISPLAY AREA ONCE ALREADY?
	JMP	INST4A	;NO, PUT SWITCH ON

	ERROR	2	;DISPLAY AREA FULL!!!

		;PUT SWITCH ON, GO BACK TO TOP OF DSPL LIST AREA
INST4A:	ISZ	INSTS	;SWITCH ON
	LDA	D,CAVAIL	;PTR TO TOP OF LIST AREA
	JMP	INST4



		;FREE BLOCK FOUND
		;FIRST, SEE IF IT IS LONG ENOUGH TO ACCOMODATE
		;DISPLAY LIST.  THEN SEE IF IT IS ONE LONGER THAN DISPLAY LIST.
		;IF SO DO NOT USE.  IF IT EXACTLY EQUALS
		;DISPLAY LIST, FIX POINTER TO NEXT FREE BLOCK (EXCEPT
		;IF IT IS FIRST BLOCK.

		;IS THIS LEGAL LOCATION?
INST5:	STA D,INDST		;(DLB>LEGAL LOCS>DLT)
	LDA A,CDLT
	LDA B,CDLB
	JSR @CDLIM
	LDA D,INDST

	LDA	A,0(C)	;LENGTH OF FREE BLOCK
	LDA	B,INLEN	;LENGTH TO BE INSERTED
	SUBZ	B,A(SZC)	;A<B?  BLOCK TOO SMALL?
	JMP	INST6	;NO, SEE IF ONLY ONE LOCATION LEFT.

INST5A:	MOV	C,D	;YES--CHECK NEXT FREE BLOCK
	JMP	INST4

INST6:	MOV	A,B	;REMAINING LOCATIONS
	SUBZL	A,A	;ONE IN A
	SUB%	B,A(SNR)	;ONLY ONE LOCATION LEFT?
	JMP	INST5A	;YES--DONT USE THIS BLOCK

	MOV%	B,B(SZR)	;AREA EXACTLY FILLED?
	JMP	INST7	;NO, FIX ROV+1 AND TRANSFER LIST TO BLOCK

	LDA	A,AVAIL+1	;YES
	SUB%	A,C(SNR)	;FIRST BLOCK?
	JMP	INST5A	;YES, DON'T OBLITERATE IT

	LDA	A,1(C)	;NO--CHANGE POINTERS
	STA	A,1(D)

;FALLS THROUGH


		;FIX POINTER TO LAST BLOCK FILLED
		;DO BLOCK TRANSFER OF LIST TO LIST AREA, AND RETURN TO
		;CALLING ROUTINE

INST7:	LDA	A,1(D)	;ROVING PTR PTS TO PREVIOUS BLOCK

	STA	B,0(C)	;FREE STORAGE LEFT IN BLOCK
	STA	A,ROV+1	;PNTR TO PREVIOUS BLOCK

	ADD	B,C
	LDA	D,R	;DLIST PTR PTS TO RESERVED BLOCK
	STA	C,1(D)
	LDA	B,STIME	;SET FRAME TIME
	STA	B,0(D)
	STA	C,INDST
	SUB	A,A
	STA	A,2(D)
	STA	A,3(D)
	JSR	@CBLT	;DO BLOCK TRANSFER OF DISPLAY LIST
INLEN:		0	;ARGS FOR BLT--LENGTH
INADR:		0	;SOURCE BLOCK
INDST:		0	;DEST BLOCK

	JMP	@INRET	;BLT RETURNS HERE
INRET:		0
INSTS:		0

AVAIL:		0
		DLT
ROV:		0
		0


;TEN ERROR--
;SENDS ERROR MESSAGES TO TEN
;CALLED WITH CODE IN ACC A

TENERR:	LDA	B,[100]	;TURN ON HIGH ORDER BIT TO AVOID MESSING UP ITS
	ADD	B,A	;ADD TO ERROR MESSAGE
	SKPBZ	PDPO	;WAIT TILL PDP OUT NOT BUSY
	JMP 	.-1
	DOAS	A,PDPO	;SEND ERROR CODE TO PDP10
	SUB	A,A
	STA	A,SHIPFL	;FIX THIS IN CASE
	STA	A,GETFL
	SUBZL	A,A	;SET ERROR FLAG
	STA	A,ERRFL
	LDA	C,CPQ	;IGNORE REST OF QUEUE
	LDA	B,0(C)
	STA	B,1(C)
	STA	B,2(C)
	LDA	A,STIME
	INCL%	A,A(SNC)	;SEE IF THIS HAS BEEN MESSED UP BY SHIP
	JMP	@CONTIN	;SNAP NAME HAS HIGH BIT ON AND IS NOT -1

	LDA	A,@CLISTN	;YES, RESTORE
	STA	A,STIME
	JMP	@CONTIN

CLISTN:	LISTN

;ERRORS--
;1-TOO MANY LISTS
;2-LISTS TOO LONG
;3-LIST BEING "SHIPPED" TOO LONG
;4-MORE OF THE SAME


;FRAME--
;DECREMENT FRAME TIME OF ALL ACTIVE LISTS
;NOT INFINITELY DISPLAYED

FRAM:	STA	D,FRAMR	;DECREMENT FRAME TIMES
	LDA	C,CTOP	;ADDR OF DSPLL
FRAM1:	LDA	A,0(C)	;NEXT FRAME TIME
	MOV%	A,A(SNR)	;ZERO?
	JMP	FRAM2	;YES
	MOVL%	A,A(SZC)	;NO--NEGATIVE?
	JMP	FRAM2	;YES
	DSZ	0(C)	;DECREMENT
	JMP	FRAM2
	LDA	A,2(C)
	MOV%	A,A(SZR)
	JMP	FRAM1B	;THIS IS A REFERENCE
FRAM1A:	LDA	D,1(C)	;REMOVE FROM DSPL IF ZERO
	STA	D,PO	;ADDR OF BLOCK TO BE REMOVED
	STA	C,CTEMP	;SAVE POSITION IN DSPLL
	LDA	A,0(D)	;LENGTH OF BLOCK
	STA	A,N
	JSR	REM
	LDA	C,CTEMP
FRAM1B:	SUB	A,A
	STA	A,1(C)	;CLEAR OUT ADDRESS
	STA	A,2(C)
	STA	A,3(C)
FRAM2:	LDA	B,[4]
	ADD	B,C
	LDA	B,CBOT
	SUBZ%	B,C(SZC)	;C<=CBOT?
	JMP	@FRAMR	;NO--RETURN
	JMP	FRAM1	;YES TEST NEXT
FRAMR:		0


;REMOVE--
;REMOVE LIST FROM DISPLAY LIST AREA
;AND RESET POINTERS

REM:	STA	D,REMRET
	LDA A,CDLT
	LDA B,CDLB
	LDA C,PO
	JSR @CDLIM

	LDA	A,PO
	LDA	C,CAVAIL	;ADDR OF AVAIL
REM2:	LDA	D,1(C)	;ARRD OF NEXT FREE BLOCK
	MOV%	D,D(SNR)	;NULL?
	JMP	REM4
	SUBZ%	D,A(SNC)	;ARE WE PAST BLOCK TO BE DELETED?
	JMP	REM3
	MOV	D,C	;NO--CHUG DOWN LIST
	JMP	REM2
REM3:	STA	C,CTEMP1
	LDA	B,N	;LENGTH OF BLOCK
	ADD	B,A
	SUB%	D,A(SZR)	;CHECK UPPER BOUND
	JMP	REM4

	LDA	A,ROV+1	;ARE WE INCREASING LENGTH OF FREE BLOCK ON TOP?
	SUB%	A,D(SZR)
	JMP	REM3A	;NO

	SUB	A,A	;YES
	STA	A,ROV+1	;RE-INITIALIZE POINTER

REM3A:	LDA	A,0(D)	;N_N+LENGTH OF NEXT BLOCK
	ADD	A,B
	STA	B,N
	LDA	D,1(D)	;PTR TO NEXT FREE BLOCK
	LDA	C,PO	;STORE IN 2ND WD OF FREED BLOCK
	STA	D,1(C)
	JMP	REM5


REM4:	STA	C,CTEMP1
	LDA	C,PO	;FIX PTR
	STA	D,1(C)
REM5:	LDA	C,CTEMP1
	LDA	D,0(C)	;CHECK LOWER BOUND
	LDA	B,PO
	ADD	C,D
	SUB%	B,D(SZR)
	JMP	REM6
	LDA	A,N
	LDA	D,0(C)
	ADD	D,A
	MOV	B,D
	STA	A,0(C)
	LDA	A,1(D)
	STA	A,1(C)
	JMP	@REMRET
REM6:	MOV	B,D
	STA	B,1(C)
	LDA	A,N
	STA	A,0(D)
	JMP	@REMRET
REMRET:		0

;DRAW--
;COMPILE LIST CONSISTING OF STRAIGHT
;LINE FROM XF,YF TO XT,YT
;LIST STARTS AT DROUT, WHICH CONTAINS LENGTH

DRAAD:	STA	D,DRARET	;CALL HERE TO APPEND LIST
	LDA	A,DRASV	;GET LAST LIST WORD
	LDA	B,SBMFL	;WAY BEAM SHOULD BE
	LDA	C,DBMFL	;WAY BEAM IS
	SUB%	B,C(SZR)	;COMPLEMENT BEAM?
	JSR	@CDRBM	;YES

	STA	B,DBMFL
	LDA	D,XF
	LDA	C,YF
	JMP	DRAW1

DRAW:	STA	D,DRARET	;STORE RETURN ADDRESS IN PAGE 0
	
	LDA	D,CDROUT	;SET UP SELF-INCREMENTING COUNTER
	STA	D,20
	LDA	B,[1777]

	SUB	A,A	;OUTPUT NULL CHARACTER
	STA	A,@20
	STA	A,XDIR
	STA	A,YDIR

	LDA	D,XF	;XCOORDINATE INSTRUCTION
	AND	B,D
	SUBZR	A,A
	ADD	D,A
	STA	A,@20

	LDA	C,YF	;YCOORDINATE INSTRUCTION
	AND	B,C
	LDA	A,[120000]
	ADD	C,A
	STA	A,@20
	LDA	A,[DRANEW]	;CODE MODE

	MOV	D,B
	JSR	@CDRBM
	MOV	B,D

;FALLS THROUGH

;FALLS IN

DRAW1:	LDA	B,XT
	MOVL%	B,B(SZC)	;SEE IF XT IS NEGATIVE
	JMP	@CDRAX	;YES
	SUBZ	D,B(SZC)	;NO,IS .DX NEGATIVE?
	JMP	DRAW1A	;NO
	NEG	B,B	;YES
	JMP	@CDRAX1

DRAW1A:	LDA	D,XDIR	;GET X DEFLECTION
	MOV%	D,D(SZR)
	JMP	@CDRAX2	;COMPLEMENTED, RESTORE

DRAW2:	LDA	D,YT	;SAME FOR .DY
	MOVL%	D,D(SZC)
	JMP	@CDRAY	;YT IS NEGATIVE
	NEGZ	C,C
	ADD	D,C(SNC)	;IS .DY NEGATIVE?
	JMP	@CDRAY1	;YES

	LDA	D,YDIR	;GET Y DEFLECTION
	MOV%	D,D(SZR)
	JMP	@CDRAY2	;COMPLEMENTED, RESTORE
	JMP	DRAW2A

CDRAX:		DRARX
CDRAX1:		DRARX1
CDRAX2:		DRARX2
CDRAY:		DRARY
CDRAY1:		DRARY1
CDRAY2:		DRARY2


			;DX IN B, DY IN C
DRAW2A:	MOVZR	B,B	;DIVIDE DX AND DY BY 2
	MOVZR	C,C
	ADD%	B,C(SNR)	;SEE IF BOTH DX AND DY ARE 0
	JMP	DRATR

	LDA	D,SHIPFL
	MOV%	D,D(SNR)	;SKIP FOLLOWING GOOK IF NOT SHIPPING
	JMP	DRAW3

	STA	A,DRASV	;SAVE A
	LDA	A,XDIR	;MAKE NEW XF 2*((XF/2)+(DX/2))
	LDA	D,XF	;THIS ROUTINE TO MAKE NOVA THINK
	MOVZR	D,D	;IT IS WHERE IT IS!!
	MOV%	A,A(SNR)
	ADDZL	B,D(SKP)	;DX>0 ADD DX TO XF
	SUBZL	B,D
	STA	D,XF

	LDA	A,YDIR	;SAME FOR YF
	LDA	D,YF
	MOVZR	D,D
	MOV%	A,A(SNR)
	ADDZL	C,D(SKP)
	SUBZL	C,D
	STA	D,YF

	LDA	A,DRASV	;RECLAIM

;FALLS THROUGH

DRAW3:	SUBZ%	B,C(SZC)	;CALCULATE DY-DX
	JMP	DRAHZY		;DY .GE. DX

	MOV	B,D	;DX>DY, B>D
	MOV	C,B	;PUT DX=S IN ACC D, DY=R IN ACC B
	LDA	C,DRAZ	;MAKE HRZ INSTRUCTION COUNT X
	STA	C,DRAHRZ
	LDA	C,DRAO
	JMP	DRAW4

DRAHZY:	MOV	C,D
	LDA	C,DRAO	;DY=S IN ACC D, DX=R IN ACC B
	STA	C,DRAHRZ	;MAKE HRZ INSTRUCTION COUNT Y
	LDA	C,DRAZ

DRAW4:	STA	C,DRAHRZ+1
	STA	D,DRACNT	;SET UP COUNTER

	LDA	C,SHIPFL
	MOV%	C,C(SNR)	;SHIPPING?
	JMP	DRAW5	;NO

	STA	A,DRASV
	MOV	B,D	;SAVE B
	LDA	B,DRACNT
	SUB	A,A
	LDA	C,[7]
	DIV		;C/(A_16 +B)=B REM A

	LDA	A,20
	ADD	A,B
	INC	B,B
	INC	B,B	;HIGHEST POSSIBLE ADDRESS
	LDA	A,[LOADER]	;ADDRES OF LOADER
	SUBZ%	A,B(SZC)	;LIST TOO LONG?
	JMP	DRAW6	;YES

	MOV	D,B	;NO, RESTORE B
	LDA	A,DRASV	;RECLAIM LAST INSTRUCTION OF LAST LIST
	LDA	D,DRACNT	;D

DRAW5:	MOV	B,C	;R IN ACC C
	JMP	DRALP1	;ENTER BASIC ASSEMBLING LOOP

DRAW6:	ERROR	3	;LIST TOO LONG!!!


DRAT:	0		;TEMP STORAGE
DRALP:	ADD	C,B	;BASIC ASSEMBLING LOOP
	MOVL%	A,A(SNC)	;SEE IF PACKED WORD IS FULL
	JMP	DRALP1	;WORD NOT FULL

	STA	A,@20	;STORE OLD WORD
	LDA A,20
	STA B,DRAT
	LDA B,[LOADER]
	SUBZ% B,A(SNC)
	JMP DRALP0
	ERROR 4

DRALP0:	LDA B,CDROUT	;SEE THAT STUFF IS >DROUT
	SUBZ% A,B(SZC)
	HALT

	LDA B,DRAT
	LDA	A,[DRANEW]	;START NEW WORD

DRALP1:	STA	B,DRAT	;SAVE DR, ORIGINAL ENTRY TO LOOP
	MOVZL	B,B(SZC)	;2*DR
	JMP	DRAHRZ	;DR IS NEGATIVE
	ADCZ%	D,B(SNC)	;2*DR-S
	JMP	DRAHRZ	;2*DR.LE.S

	MOVOL	A,A	;2*DR>S
	MOVOL	A,A	;DIAGONAL INSTRUCTION
	LDA	B,DRAT	;RESTORE DR
	SUB	D,B	;DR-S
	JMP	DRALP2

DRAHRZ:	0		;HRZ INSTRUCTION FROM DRASO GOES HERE
	0		;AND HERE
	LDA	B,DRAT	;RESTORE DR

DRALP2:	DSZ	DRACNT	;SEE IF MORE INSTRUCTIONS ARE LEFT
	JMP	DRALP

;FALLS THROUGH


;FALLS IN

DRATR:	LDA	C,SHIPFL
	MOV%	C,C(SZR)	;SHIPPING?
	JMP	DRATR2	;YES

DRATRA:	JSR	DRBM	;BEAM OFF

DRATR0:	LDA	B,[DRANEW]
	SUB%	A,B(SNR)	;IS WORD ONLY CODE MODE?
	JMP	DRATR1
	JSR	DRALJ	;NO, LEFT JUSTIFY & STORE

DRATR1:	LDA	B,20	;CALCULATE LENGTH OF ASSEMBLED PROGRAM
	LDA	A,CDROUT
	SUB	A,B
	INC	B,B
	STA	B,@CDROUT
	STA	B,DRLEN	;SAVE LENGTH
	JMP	@DRARET	;RETURN TO CALLING PROGRAM


DRATR2:	JSR	DRAFU	;IS WORD FULL?
	STA	A,DRASV	;SAVE CURRENT WORD
	JMP	@DRARET	;RETURN

DRARX:	NEG	B,B
	ADD	D,B	
DRARX1:	LDA	D,XDIR
	MOV%	D,D(SZR)
	JMP	@DRAXR	;ALREADY COMPLEMENTED
DRARX2:	JSR	DRA4S	;MAKE ROOM FOR 4 BITS
	ADDZL	A,A	;COMPLEMENT X DEFLECTION COUNTER
	MOVZL	A,A
	MOVOL	A,A
	LDA	D,XDIR
	COM	D,D
	STA	D,XDIR
	JSR	DRAFU	;WORD FULL?
	JMP	@DRAXR

DRAXR:		DRAW2


DRARY:	SUB	D,C(SKP)	;YT<0, SKIP NEXT INSTRUCTION	
DRARY1:	NEG	C,C
	LDA	D,YDIR
	MOV%	D,D(SZR)
	JMP	@DRARYR	;Y DEFLECTION ALREADY COMPLEMENTED
DRARY2:	JSR	DRA4S	;MAKE ROOM FOR 4 BITS
	ADDZL	A,A	;COMPLEMENT Y DEFLECTION COUNTER
DRAO:	MOVOL	A,A	;INSTRUCTIONS GO TO DRAHRZ FROM HERE
DRAZ:	MOVZL	A,A	;AND HERE
	LDA	D,YDIR
	COM	D,D
	STA	D,YDIR
	JSR	DRAFU	;WORD FULL?
	JMP	@DRARYR

DRARYR:	DRAW2A


DRBM:	STA	D,DRBMR
	JSR	DRA4S	;SPACE FOR 4 BITS?
	ADDZL	A,A	;CHANGE BEAM
	MOVOL	A,A
	MOVOL	A,A
	JSR	DRAFU	;WORD FULL?
	JMP	@DRBMR

DRBMR:	0

DRA4S:	STA	D,DRALJR	;SEE IF ROOM FOR 4 BITS
	LDA	D,[17_12.]
	AND%	D,A(SNR)
	JMP	@DRALJR	;YES, RETURN
	JMP	DRALJ1

DRALJ:	STA	D,DRALJR	;LEFT JUSTIFY
DRALJ1:	MOVZL	A,A(SNC)
	JMP	DRALJ1
	MOVR	A,A
	STA	A,@20
	LDA	A,[DRANEW]
	JMP	@DRALJR

DRALJR:	0


DRAFU:	MOVL%	A,A(SNC)	;WORD FULL?
	JMP	0(D)	;NO
	STA	A,@20	;YES, STORE
	LDA	A,[DRANEW]	;START NEW WORD
	JMP	0(D)

;IN QUEUE--
;INSERT 8 BIT WORD INTO PDP10 QUEUE

INQ:	LDA	C,RPQ	;INSERT IN PDP-10 QUEUE
	LDA	B,CPQBOT
	SUBZ%	B,C(SNC)	;IF AT BOTTOM
	JMP	INQ1
	LDA	C,CPQTOP	;MOVE TO TOP
	JMP	.+2
INQ1:	INC	C,C
	LDA	B,FPQ
	SUB%	B,C(SNR)
	JMP	INQ2	;QUEUE OVERFLOW

	STA	A,0(C)
	STA	C,RPQ
	JMP	0(D)

INQ2:	HALT
	JMP	@CRESET

;OUT QUEUE--
;TAKE 8 BIT WORD FROM PDP10 QUEUE TO
;ACC A

OUTQ:	INTDS
	LDA	C,FPQ
	LDA	B,RPQ
	SUB%	B,C(SNR)	;IF FRONT = REAR Q EMPTY
	JMP	OUTQ2+1
	SUBZ%	B,C(SNC)
	JMP	OUTQ1
	LDA	C,CPQTOP
	JMP	.+2
OUTQ1:	INC	C,C
	LDA	A,0(C)
	STA	C,FPQ

OUTQ2:	INC	D,D
	INTEN
	JMP	0(D)

CPQBOT:		PQBOT
CPQTOP:		PQTOP
RPQ:		PQTOP
FPQ:		PQTOP


;DELIMIT--
;SUBROUTINE CHECKS THAT
;C IS WITHING LEGAL BOUNDS

DLIM:	ADCZ% C,A(SZC)	;IS C<A?
	HALT	;YES

	ADCZ% B,C(SZC)	;B<C?
	HALT	;YES

	JMP 0(D)

;IF THIS HALTS:
;A/ LOWEST LEGAL ADDRESS
;B/ HIGHEST LEGAL ADDRESS
;C/ ADDRESS TESTED
;D/ ADDRESS CALLED FROM +1


;BLOCK AND BUFFERS--

;PDP10 QUEUE
PQTOP:	LOC	.+20
PQBOT:		0


;LIST OF LISTS
DLLT:	LOC	.+LLEN-1
DLLB:		0


;DISPLAY LIST AREA
DLT:		LEN
	LOC	.+LEN-2
DLB:		0


;POINTER AREA
PTBUF:		2
	LOC	.+300


;DRAW BUFFER
DROUT:		0

	LOC	22
	CONSTA

	END	0