; from part 1 of LLL BASIC interpreter article

lREM" THIS ROUTINE WILL PLOT A SET OF AXIS AND A QUADRATIC FUNCTION
2REM" ON A DISPLAY AND THE~ LABEL IT. IT USES A 4 USER WRITTEN
3REK" SUB-ROUTlNE5:
4REM
5REM" CALL (I,X,Y,C) - PLACES C IN COLUMN X, ROW Y OF THE DISPLAY
6REM" WHERE C IS AN ASCII CODED CHARACTER
7REM
8REM" CALL(2,A(0)) - READS A CHARACTER STRING FROM THE TTY AND STORES
9REM" IT IN ARRAY A
lOREM
llREM" CALL(3,A(0)) - WRITES THE CHARACTER STRING STORED IN ARRAY A
12REM" TO THE DISPLAY
13REM
14REM" CALL(4) - CLEARS THE DISPLAY
lSREM
16REM" START OF PROGRAM
17REM
18REM" RESERVE STORAGE AREA FOR TITLE
20DIMA(10)
30REM" CLEAR SCREEN
40CALL(4)
S0REM" ASK FOR AND INPUT TITLE
SSPRINT"WHAT SHOULD PLOT BE LABELED?";
60CALL(2,A(0))
70REM" DRAW AXIS
80GOSUB500
90REM" PLOT FUNCTION
100LETX=-29
110GOSUB1000
120CALL( I, 31+X,8-Y, 248)
130LETX-X+1
140IFX><31 THENll0
150REM" OUTPUT TITLE
160CALL(3,A(0) )
165REM" WE'RE DONE
170STOP

500REM" THIS SUB. WILL DRAW A SET OF AXIS
505LETX-l
510LETY-7
520LETC-I73
530CALL(I,X. Y .C)
540LETX-X+1
550IFX><65THEN530
560LETX=31
570LETY-l
575LETC=252
580CALL(1,X, Y ,C)
590LETY=Y+1
600IFY><17THEN500
610RETURN

1000REM" GIVEN X nus SUB. CALCULATES (17/900)*X**2-8
1005REM" FIRST CHECK IF X=0 AS iT WILL "UPSET FLT. PHT. PACK.
1010IFX="THEN1045
1015REM" WE'RE OK - CALCULATE FUNCTION
1020LETY=X*X
1025LETK"17/900
1030LETY=Y*K
1035LETY=Y-R
1040RETURN
1045LETY=-8
1050RETURN '"'END READY 


;ASSEMBLY LANGUAGE PROGRAM, DEFINE EXTERNALS
FIX EQU 14912Q
COPDH EQU 13212Q
FREG1 EQU 16567Q
 ORG 16614Q
 DW SBEND
; ENTRIES IN SUB TABLE
 DB 1
 DW SCOPE
 DB 2
 DW SUB2
 DB 3
 DW SUB3
 DB 4
 DW SUB4
 DB 377Q ;NO MORE ENTRYS
;THE CALL TO THIS ROUTINE IS OF THE FORM
; CALL(l X Y C)
;THE VALUE OF C IS PLACED IN COLUMN X LINE Y
;OF THE DISPLAY
SCOPE: POP D
 LXI H,FREG1
 CALL COPDH
 XCHG
 CALL FIX
 INX D
 INX D
 INX D
 LDAX D
 MOV B,A
 POP D
 LXI H,FREG1
 CALL COPDH
 XCHG
 CALL FIX
 INX D
 INX D
 INX D
 LDAX D
 MOV C,A
 POP D
 LXI H,FREG1
 CALL COPDH
 XCHG
 CALL FIX
 INX D
 INX D
 INX D
 LDAX D
 LXI H,135377Q
 LXI D,1000Q 
LUP:  DCR C
 JZ ADINC
 DAD D
 JMP LUP
ADINC: MOV E,A
 DAD D
 MOV M,B
 RET
;SUB2 READS A TITLE FROM TTY VIA ODT
READ: EQU 333Q
SUB2: POP H
 PUSH H
 MVI C,0
LUP2: INX H
 CALL REED
 CPI 215Q
 JZ DUN2
 INR C
 MOV M,A
 JMP LUP2
DUN2: POP H
 MOV M,C
 MVI A, 212Q
 RST 6
 RET
;SUB3 WRITES TITLE TO DISPLAY
SUB3: POP H
 LXI D, 137741Q
 MOV C,M
 INX H
LUP3: MOV A,M
 STAX D
 INX H
 INX D
 DCR C
 JNZ LUP3
;SUB4 CLEARS SCREEN
SUB4: LXI H, 136000Q
 MVI A,240Q
 MVI D,0
 MVI C,4
LUP4: MOV M,A
 INX H
 DCR D
 JNZ LUP4
 DCR C
 JNZ LUP4
 RET
SBEND EQU $
 END