mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
synced 2024-06-16 22:29:31 +00:00
317 lines
12 KiB
NASM
317 lines
12 KiB
NASM
*
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*``````````````````````````````*
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* TCIRCLE (NATHAN RIGGS) *
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* *
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* INPUT: *
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* *
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* ZPW1 = X CENTER POS *
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* ZPW2 = Y CENTER POS *
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* ZPB1 = RADIUS *
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* ZPB2 = FILL CHARACTER *
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* *
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* OUTPUT: *
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* *
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* USES BRESENHAM'S CIRCLE *
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* ALGORITHM TO DRAW A CIRCLE *
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* TO THE 40-COLUMN TEXTMODE *
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* SCREEN. *
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* *
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* DESTROY: NZCIDV *
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* *
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* *
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* CYCLES: 601+ *
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* SIZE: 371 BYTES *
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* *
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* SUBSTANTIAL DEBT IS OWED TO *
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* MARC GOLOMBECK AND HIS GREAT *
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* IMPLEMENTATION OF THE *
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* BRESENHAM CIRCLE ALGORITHM *
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* IN 6502 AND APPLESOFT, WHICH *
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* IS BASED ON THE GERMAN LANG *
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* VERSION OF WIKIPEDIA'S ENTRY *
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* ON THE ALGORITHM THAT HAS A *
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* BASIC PSEUDOCODE EXAMPLE. *
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* THAT EXAMPLE, WITH CHANGED *
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* VARIABLE NAMES, IS INCLUDED *
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* BELOW. *
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*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
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*
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]XC EQU ZPW1 ; X CENTER POSITION
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]YC EQU ZPW2 ; Y CENTER POSITION
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]R EQU ZPB1 ; RADIUS
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]F EQU ZPB2 ; FILL CHAR
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*
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]Y EQU ZPW3 ; CENTER YPOS
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]X EQU ZPW3+1 ; CENTER XPOS
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]DY EQU ZPW4 ; CHANGE IN Y
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]DX EQU ZPW4+1 ; CHANGE IN X
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]ERR EQU ZPW5 ; ERROR VALUE
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]DIAM EQU ZPW5+1 ; DIAMETER
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]XT EQU ZPW6 ; INVERTED X VALUE
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]YT EQU ZPW6+1 ; INVERTED Y VALUE
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*
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********************************
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* *
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* BASIC PSEUDOCODE *
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* *
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********************************
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*
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* X = R
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* Y = 0
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* ERROR = R
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* SETPIXEL XC + X, YC + Y
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* WHILE Y < X
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* DY = Y * 2 + 1
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* Y = Y + 1
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* ERROR = ERROR - DY
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* IF ERROR < 0 THEN
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* DX = 1 - X * 2
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* X = X - 1
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* ERROR = ERROR - DX
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* END IF
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* SETPIXEL XC + X, YC + Y
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* SETPIXEL XC - X, YC + Y
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* SETPIXEL XC - X, YC - Y
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* SETPIXEL XC + X, YC - Y
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* SETPIXEL XC + Y, YC + X
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* SETPIXEL XC - Y, YC + X
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* SETPIXEL XC - Y, YC - X
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* SETPIXEL XC + Y, YC - X
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* WEND
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*
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********************************
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*
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TCIRCLE
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*
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** FIRST, INITIALIZE VARIABLES
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*
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LDA #0 ; {2C2B} CLEAR YPOS {NZ}
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STA ]Y ; {4C3B}
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LDA ]R ; {4C3B} LOAD RADIUS {NZ}
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STA ]X ; {4C3B} X = RADIUS
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STA ]ERR ; {4C3B} ERROR = RADIUS
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ASL ; {2C1B} R * 2 {NZC}
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STA ]DIAM ; {4C3B} STORE DIAMETER
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*
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** NOW DRAW FIRST PART OF CIRCLE
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*
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** CALCULATE -X AND -Y
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*
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LDA ]X ; {4C3B} GET XPOS {NZ}
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NEGA ; {6C5B} {NZCV}
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STA ]XT ; {4C3B} STORE NEGATED IN XT
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LDA ]Y ; {4C3B} GET YPOS {NZ}
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NEGA ; {6C5B} {NZCV}
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STA ]YT ; {4C3B} STORE NEGATED IN YT
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*
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** PLOT XC+X,YC
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*
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LDA ]XC ; {4C3B} LOAD CIRCLE CENTER XPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]X ; {4C3B} ADD CURRENT XPOS {NZCV}
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TAY ; {2C1B} TRANSER TO .Y {NZ}
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TAX ; {2C1B} AND .X {NZ}
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LDA ]YC ; {4C3B} LOAD CIRCLE CENTER YPOS {NZ}
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JSR GBCALC ; {43C3B} GET X,Y SCREEN MEMORY POS
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LDA ]F ; {4C3B} LOAD FILL CHAR {NZ}
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STA (GBPSH),Y ; {5C3B} STORE IN SCREEN MEMORY
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*
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** PLOT XC-X,YC
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*
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LDA ]XC ; {4C3B} LOAD CIRCLE CENTER XPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]XT ; {4C3B} ADD NEGATED CURRENT XPOS {NZCV}
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TAX ; {2C1B} TRANSFER TO .X {NZ}
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TAY ; {2C1B} AND .Y {NZ}
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LDA ]YC ; {4C3B} LOAD CIRCLE CENTER YPOS {NZ}
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JSR GBCALC ; {43C3B} GET X,Y SCREEN MEMORY POS
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LDA ]F ; {4C3B} LOAD FILL CHAR {NZ}
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STA (GBPSH),Y ; {5C3B} STORE IN SCREEN MEMORY
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*
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** PLOT XC,YC+X
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*
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LDA ]XC ; {4C3B} LOAD CIRCLE CENTER XPOS {NZ}
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TAY ; {2C1B} TRANSFER TO .Y {NZ}
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TAX ; {2C1B} AND .X {NZ}
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LDA ]YC ; {4C3B} LOAD CIRCLE CENTER YPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]X ; {4C3B} ADD CURRENT XPOS {NZCV}
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JSR GBCALC ; {43C3B} GET X,Y SCREEN MEMORY POS
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LDA ]F ; {4C3B} LOAD FILL CHAR {NZ}
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STA (GBPSH),Y ; {5C3B} STORE IN SCREEN MEMORY
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*
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** PLOT XC,YC-X
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*
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LDA ]XC ; {4C3B} LOAD CIRCLE CENTER XPOS {NZ}
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TAY ; {2C1B} TRANSFER TO .Y {NZ}
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TAX ; {2C1B} AND .X {NZ}
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LDA ]YC ; {4C3B} LOAD CIRCLE CENTER YPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]XT ; {4C3B} ADD NEGATED CURRENT XPOS {NZCV}
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JSR GBCALC ; {43C3B} GET X,Y SCREEN MEMORY POS
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LDA ]F ; {4C3B} LOAD FILL CHAR {NZ}
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STA (GBPSH),Y ; {5C3B} STORE IN SCREEN MEMORY
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*
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** NOW LOOP UNTIL CIRCLE IS FINISHED
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*
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:LOOP
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*
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** CHECK IF CIRCLE FINISHED
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*
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LDA ]Y ; {4C3B} IF Y > X {NZ}
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CMP ]X ; {4C3B} {NZC}
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BCC :LPCONT ; {3C2B} CONTINUE LOOPING
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JMP :EXIT ; {3C3B} OTHERWISE, CIRCLE DONE
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:LPCONT
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:STEPY ; STEP THE Y POSITION
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LDA ]Y ; {4C3B} LOAD YPOS {NZ}
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ASL ; {2C1B} MULTIPLY BY 2 {NZC}
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*CLC
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ADC #1 ; {3C2B} ADD +1 {NZCV}
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STA ]DY ; {4C3B} STORE CHANGE OF Y
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INC ]Y ; {6C3B} INCREASE YPOS {NZ}
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LDA ]DY ; {3C2B} NEGATE {NZ}
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NEGA ; {6C5B} {NZCV}
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ADC ]ERR ; {4C3B} ADD ERR {NZCV}
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STA ]ERR ; {4C3B} ERR = ERR - DY
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BPL :PLOT ; {3C2B} IF ERR IS +, SKIP TO PLOT
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:STEPX
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LDA ]X ; {3C2B} LOAD XPOS {NZ}
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ASL ; {2C1B} MULTIPLY BY 2 {NZC}
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NEGA ; {6C5B} NEGATE {NZCV}
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ADC #1 ; {3C2B} (X*2) + 1 {NZCV}
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STA ]DX ; {4C3B} STORE CHANGE OF X
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DEC ]X ; {6C3B} DECREASE YPOS {NZ}
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LDA ]DX ; {3C2B} NEGATE {NZ}
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NEGA ; {6C5B} {NZCV}
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ADC ]ERR ; {4C3B} ADD ERR {NZCV}
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STA ]ERR ; {4C3B} ERR = ERR - DX
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*
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:PLOT
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*
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** NOW CALCULATE -X AND -Y
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*
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LDA ]X ; {3C2B} {NZ}
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NEGA ; {6C5B} NEGATE {NZCV}
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STA ]XT ; {4C3B}
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LDA ]Y ; {3C2B} {NZ}
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NEGA ; {6C5B} NEGATE {NZCV}
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STA ]YT ; {4C3B}
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*
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** NOW PLOT CIRCLE OCTANTS
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*
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** PLOT XC+X,YC+Y
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*
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LDA ]XC ; {3C2B} LOAD CIRCLE CENTER XPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]X ; {4C3B} ADD CURRENT XPOS {NZCV}
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TAY ; {2C1B} TRANSFER TO .Y {NZ}
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TAX ; {2C1B} AND .X {NZ}
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LDA ]YC ; {3C2B} LOAD CIRCLE CENTER YPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]Y ; {4C3B} ADD CURRENT YPOS {NZCV}
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JSR GBCALC ; {43C3B} GET X,Y SCREEN ADDRESS {NZCV}
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LDA ]F ; {3C2B} LOAD FILL CHAR {NZ}
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STA (GBPSH),Y ; {6C2B} STORE AT SCREEN ADDRESS
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*
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** PLOT XC-X,YC+Y
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*
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LDA ]XC ; {3C2B} LOAD CIRCLE CENTER XPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]XT ; {4C3B} ADD NEGATED CURRENT XPOS {NZCV}
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TAY ; {2C1B} TRANSFER TO .Y {NZ}
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TAX ; {2C1B} AND TO .X {NZ}
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LDA ]YC ; {3C2B} LOAD CIRCLE CENTER YPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]Y ; {4C3B} ADD CURRENT YPOS {NZCV}
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JSR GBCALC ; {43C3B} GET X,Y SCREEN ADDRESS {NZCV}
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LDA ]F ; {3C2B} LOAD FILL CHAR {NZ}
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STA (GBPSH),Y ; {6C2B} STORE AT SCREEN ADDRESS
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*
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** PLOT XC-X,YC-Y
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*
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LDA ]XC ; {3C2B} LOAD CIRCLE CENTER XPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]XT ; {4C3B} ADD NEGATED CURRENT XPOS {NZCV}
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TAY ; {2C1B} TRANSFER TO .Y {NZ}
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TAX ; {2C1B} AND .X {NZ}
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LDA ]YC ; {3C2B} LOAD CIRCLE CENTER YPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]YT ; {4C3B} ADD NEGATED CURRENT YPOS {NZCV}
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JSR GBCALC ; {43C3B} GET X,Y SCREEN ADDRESS {NZCV}
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LDA ]F ; {3C2B} LOAD FILL CHARACTER {NZ}
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STA (GBPSH),Y ; {6C2B} STORE AT SCREEN ADDRESS
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*
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** PLOT XC+X,YC-Y
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*
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LDA ]XC ; {3C2B} LOAD CIRCLE CENTER XPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]X ; {4C3B} ADD CURRENT XPOS {NZCV}
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TAY ; {2C1B} TRANSFER TO .Y {NZ}
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TAX ; {2C1B} AND .X {NZ}
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LDA ]YC ; {3C2B} LOAD CIRCLE CENTER YPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]YT ; {4C3B} ADD NEGATE CURRENT YPOS {NZCV}
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JSR GBCALC ; {43C3B} GET X,Y SCREEN ADDRESS {NZCV}
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LDA ]F ; {3C2B} LOAD FILL CHAR {NZ}
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STA (GBPSH),Y ; {6C2B} STORE AT SCREEN ADDRESS
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*
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** PLOT XC+Y,YC+X
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*
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LDA ]XC ; {3C2B} LOAD CIRCLE CENTER XPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]Y ; {4C3B} ADD CURRENT YPOS {NZCV}
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TAX ; {2C1B} TRANSFER TO .X {NZ}
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TAY ; {2C1B} AND .Y {NZ}
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LDA ]YC ; {3C2B} LOAD CIRCLE CENTER YPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]X ; {4C3B} ADD CURRENT XPOS {NZCV}
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JSR GBCALC ; {43C3B} GET X,Y SCREEN ADDRESS {NZCV}
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LDA ]F ; {3C2B} LOAD FILL CHAR {NZ}
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STA (GBPSH),Y ; {6C2B} STORE AT SCREEN ADDRESS
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*
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** PLOT XC-Y,YC+X
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*
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LDA ]XC ; {3C2B} LOAD CIRCLE CENTER XPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]YT ; {4C3B} ADD NEGATED CURRENT YPOS {NZCV}
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TAX ; {2C1B} TRANSFER TO .X {NZ}
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TAY ; {2C1B} AND .Y {NZ}
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LDA ]YC ; {3C2B} LOAD CIRCLE CENTER YPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]X ; {4C3B} ADD CURRENT XPOS {NZCV}
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JSR GBCALC ; {43C3B} GET X,Y SCREEN ADDRESS {NZCV}
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LDA ]F ; {3C2B} LOAD FILL CHAR {NZ}
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STA (GBPSH),Y ; {6C2B} STORE AT SCREEN ADDRESS
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*
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** PLOT XC-Y,YC-X
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*
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LDA ]XC ; {3C2B} LOAD CIRCLE CENTER XPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]YT ; {4C3B} ADD NEGATED CURRENT YPOS {NZCV}
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TAX ; {2C1B} TRANSFER TO .X {NZ}
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TAY ; {2C1B} AND .Y {NZ}
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LDA ]YC ; {3C2B} LOAD CIRCLE CENTER YPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]XT ; {4C3B} ADD NEGATED CURRENT XPOS {NZCV}
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JSR GBCALC ; {43C3B} GET X,Y SCREEN ADDRESS {NZCV}
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LDA ]F ; {3C2B} LOAD FILL CHAR {NZ}
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STA (GBPSH),Y ; {6C2B} STORE AT SCREEN ADDRESS
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*
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** PLOT XC+Y,YC-X
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*
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LDA ]XC ; {3C2B} LOAD CIRCLE CENTER XPOS {NZ}
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CLC ; {2C1B} CLEAR CARRY {C=0}
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ADC ]Y ; {4C3B} ADD CURRENT YPOS {NZCV}
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TAY ; {2C1B} TRANSFER TO .Y {NZ}
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TAX ; {2C1B} AND .X {NZ}
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LDA ]YC ; {3C2B} LOAD CIRCLE CENTER YPOS {NZ}
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CLC ; {2C1B} {C=0}
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ADC ]XT ; {4C3B} ADD NEGATED CURRENT XPOS {NZCV}
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JSR GBCALC ; {43C3B} GET X,Y SCREEN ADDRESS {NZCV}
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LDA ]F ; {3C2B} LOAD FILL CHAR {NZ}
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STA (GBPSH),Y ; {6C2B} STORE AT SCREEN ADDRESS
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JMP :LOOP ; {3C3B} LOOP UNTIL FINISHED
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:EXIT
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RTS ; {6C1B}
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