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10-02-89/T\Pen04
This website contains an archive of files for the Acorn Electron, BBC Micro, Acorn Archimedes, Commodore 16 and Commodore 64 computers, which Dominic Ford has rescued from his private collection of floppy disks and cassettes.
Some of these files were originally commercial releases in the 1980s and 1990s, but they are now widely available online. I assume that copyright over them is no longer being asserted. If you own the copyright and would like files to be removed, please contact me.
| Tape/disk: | Home » CEEFAX disks » telesoftware12.adl |
| Filename: | 10-02-89/T\Pen04 |
| Read OK: | ✔ |
| File size: | 3D7F bytes |
| Load address: | 0000 |
| Exec address: | FFFFFFFF |
File contents
Using a light pen with the BBC microcomputer - by - Gordon Horsington
---------------------------------------------------------------------
Module 4. Using a light pen for graphics input
----------------------------------------------
The calculation of graphics coordinates is very similar to the calculation
used in module 3 to determine text coordinates except that the full
resolution of the light pen can be used in the graphics modes. A light pen
is capable of resolving a single 6845 CRTC character and the calculation
demonstrated in this module will return the graphics coordinates of the
middle of any CRTC character seen by the light pen. This calculation can
be made in all the graphics modes but it is not very meaningful to
calculate graphics coordinates in the non-graphics modes. Mode 7 has
graphics of a sort but I think they are best understood as an alternative
character set rather than as true graphics. If the algorithm described in
this module, and demonstrated in the program GRAPHIC, is used in a
non-graphics mode it will give a misleading answer. I don't this is really
a problem because there can not be any correct answer for graphics
coordinates in a non-graphics screen mode.
The table in figure 1 shows the values of the variables used in the
calculation of graphics coordinates. The values assigned to the screen
start address in this table can only be used if the screen has not been
scrolled. If the screen is scrolled the start address changes from the
values shown in figure 1. The current screen start address should
therefore be read from &350 (low byte) and &351 (high byte).
Mode start addr trim width resolution
-----+-----------+-------+-------+------------
0 | &3000 | &06 | &50 | 80 x 32
1 | &3000 | &06 | &50 | 80 x 32
2 | &3000 | &06 | &50 | 80 x 32
4 | &5800 | &04 | &28 | 40 x 32
5 | &5800 | &04 | &28 | 40 x 32
-----+-----------+-------+-------+------------
Figure 1. The start address, trim, and width for each graphics mode
-------------------------------------------------------------------
The first stage in calculating the light pen position is to determine the
value of the offset. The offset in all graphics modes is given by:
offset = trim + (screen start address DIV 8)
The CRCT X and Y coordinates can then be calculated using the appropriate
value of offset.
Y = (light pen register - offset) DIV width
X = (light pen register - offset) MOD width
A CRCT Y coordinate can be converted into a graphics Y coordinate by
multiplying it by 32 and then subtracting the product from 1008.
A CRCT X coordinate can be converted into a graphics X coordinate in modes
0 to 2 by multiplying it by 8 and then adding 8. In modes 4 and 5 a CRCT X
coordinate can be converted into a graphics coordinate by multiplying it
by 16 and then adding 16.
The values of trim and width used in these calculations are those
appropriate to the screen mode in use at the time. The screen mode
(ignoring shadow) can be read from &355. The values used for trim will, as
the name suggests, need to be trimmed as described in the earlier modules.
The values of trim used in the demonstration program GRAPHIC are those I
found to be most suitable for my light pen. You might like to edit the
program to use the values best suited to your light pen but you can also
trim the values I have used with the left and right cursor keys when the
program is running. The label offsetlow is used for the table of values
assigned to trim.
The range of the X and Y coordinates made available by this algorithm is
independant of the screen mode. The point 0,0 is always in the bottom left
of the screen and 1279,1023 is always in the top right but, because the
coordinates correspond with the centre of CRTC characters, the range
available is from 8,8 to 1271,1015 in modes 0, 1 and 2, and from 16,16 to
1263,1008 in modes 4 and 5. A maximum of two bytes are required to store
each coordinate but the machine code routine in the program GRAPHIC uses 4
bytes per coordinate so that the coordinates can be read using the BASIC !
indirection operator. The routine always returns the coordinates 0,0 if it
is called in a non-graphics mode.
The machine code routine in the demonstration program checks that the
coordinates it produces are within the expected range. This is a good idea
with non-interrupt light pen drivers because, if the pen has not been
used, the algorithm gives a very misleading answer. This is not a problem
that can occur with interrupt driven software because, by definition, the
light pen must be used to generate the light pen interrupt.
The maximum resolution of the light pen graphics coordinates is 80x32 in
modes 0, 1 and 2, but a rather chunky 40x32 in modes 4 and 5 - and
describing this as chunky is being quite generous. If you use a light pen
to draw on a graphics screen this poor resolution gives a quite shakey
looking line drawing, especially with diagonal lines. In spite of this
apparent problem it is possible to produce very smooth lines and to draw
with an acceptable level of accuracy for freehand work. If you want to use
your computer for very accurate drawing then you should use a mouse as an
input device and not a light pen.
Smooth line drawing with a light pen can be achieved by allowing the line
being drawn to lag behind the current light pen position but to always
approach the current position of the pen. This is achieved by storing the
coordinates of the last plotted position and calculating the next position
to be plotted as a fraction of the difference between the last plotted
position and the current position of the pen. This is much more simple
than it sounds and it is achieved in the program GRAPHIC in lines 210 and
220. The BASIC variables oldx and oldy are the last position plotted and
the variables newx and nexy are the next pair of coordinates to be
plotted. The variables newx and newy are always approaching xcoord and
ycoord, the current position of the light pen. The ammount of lag, and the
resultant smoothness, depends on the size of the BASIC variable divisor
(line 100). The larger the value of the divisor (used in lines 210 and
220) the greater the lag and the smoother the line. The divisor must be
the same for both X and Y otherwise circles will be drawn as elipses.
Chain the program GRAPHIC which will allow you to draw with a light pen in
any graphics screen mode. The screen modes can be selected with the up and
down cursor keys and the offset can be trimmed with the left and right
cursor keys. The size of the divisor used to smooth the line drawing can
be altered with H, for a higher value, and L for a lower value. It is
quite interesting to experiment with different divisor values. You will
probably find that a high value is required in modes 4 and 5 but a lower
value will work quite well in modes 0, 1 and 2. When divisor = 1 this is
the same as using the raw graphics coordinates. You can scroll the screen
with the Return key and change the paper and ink colours with P and I
respectively. The program is not Tube compatible but you should be able to
modify it to make it work with a second processor.
The program GRAPHIC illustrates a possible solution to the problem caused
by the occasional incorrect interpretation of the coordinates at the
extreme left and right edges of the screen. This effect was demonstrated
in module 1 but if it occurs when drawing smoothed lines it can make the
drawing look a real mess. The problem is not cured in the demonstration
program but it is suppressed by not plotting any points when the pen is at
either the extreme left edge or the extreme right edge of the screen. The
BASIC function FNswitch (lines 2330 to 2350) is used to make this
suppression. The pen is only seen as switched on if fire button 2 is open
(you might need to modify this condition) and if the current pen positon
is not at either the exteme left or the extreme right of the screen. I
will not claim that the best way of curing a problem is to suppress it in
this way but it does seem to work reasonably well if you can accept a
small reduction in the available screen area. If you remove the tests on
the X coordinate from FNswitch you will probably see the dreadful mess
this apparently trivial problem can make when you are drawing at the edge
of the screen.
10 REM> GRAPHIC
20 ON ERROR VDU23,1,1;0;0;0;:END
30 A%=&EA
40 X%=0
50 Y%=&FF
60 IF ((USR(&FFF4)AND&FF00)DIV&100)<>0 END
70 DIM mcode &100
80 PROCmcode
90 mode=2
100 divisor=4
110 paper=6
120 ink=4
130 MODE mode
140 PROCnewmode
150 REPEAT
160 REPEAT
170 oldx=newx
180 oldy=newy
190 CALL mcode
200 PRINTTAB(11,1);!xcoord;" "TAB(11,2);!ycoord;" "
210 newx=newx+((!xcoord-newx)DIV divisor)
220 newy=newy+((!ycoord-newy)DIV divisor)
230 IF FNswitch PLOT69,oldx,oldy:PLOT69,newx,newy
ELSE PLOT13,newx,newy
240 UNTIL FNswitch
250 IF INKEY(-58) PROCup:MODE mode:PROCnewmode
260 IF INKEY(-42) PROCdown:MODE mode:PROCnewmode
270 IF INKEY(-85) PROChigh
280 IF INKEY(-87) PROClow
290 IF INKEY(-56) PROCpaper
300 IF INKEY(-38) PROCink
310 IF INKEY(-26) PROCleft
320 IF INKEY(-122) PROCright
330 IF INKEY(-74) PROCscroll
340 UNTIL FALSE
350 :
360 DEFPROCscroll
370 PRINTTAB(0,31)
380 PROCdelay
390 ENDPROC
400 :
410 DEFPROCup
420 mode=mode+1
430 IF mode=3 mode=4
440 IF mode>5 mode=5
450 ENDPROC
460 :
470 DEFPROCdown
480 mode=mode-1
490 IF mode=3 mode=2
500 IF mode<0 mode=0
510 ENDPROC
520 :
530 DEFPROCleft
540 IF offsetlow?mode=12 ENDPROC
550 offsetlow?mode=offsetlow?mode+1
560 PROCdelay
570 ENDPROC
580 :
590 DEFPROCright
600 IF offsetlow?mode=0 ENDPROC
610 offsetlow?mode=offsetlow?mode-1
620 PROCdelay
630 ENDPROC
640 :
650 DEFPROCnewmode
660 VDU23,1,0;0;0;0;
670 VDU19,0,paper;0;
680 VDU19,1,ink;0;
690 GCOL3,1
700 COLOUR1
710 newx=-1
720 newy=-1
730 oldx=-1
740 oldy=-1
750 PROCdelay
760 ENDPROC
770 :
780 DEFPROClow
790 IF divisor>1 divisor=divisor DIV 2
800 PROCdelay
810 ENDPROC
820 :
830 DEFPROChigh
840 IF divisor<8 divisor=divisor*2
850 PROCdelay
860 ENDPROC
870 :
880 DEFPROCdelay
890 PRINTTAB(1,0)"Mode ";mode;SPC(8)
900 PRINTTAB(1,1)"X coord = "
910 PRINTTAB(1,2)"Y coord = "
920 PRINTTAB(1,3)"divisor = ";divisor;" "
930 PRINTTAB(1,4)"offsetlow = ";offsetlow?mode
940 time=TIME+20
950 REPEAT UNTIL time<TIME
960 ENDPROC
970 :
980 DEFPROCink
990 ink=ink+1
1000 IF ink=paper ink=ink+1
1010 IF ink>7 ink=0
1020 VDU19,1,ink;0;
1030 PROCdelay
1040 ENDPROC
1050 :
1060 DEFPROCpaper
1070 paper=paper+1
1080 IF paper=ink paper=paper+1
1090 IF paper>7 paper=0
1100 VDU19,0,paper;0;
1110 PROCdelay
1120 ENDPROC
1130 :
1140 DEFPROCmcode
1150 xcoord=&70 :REM: &70-&73
1160 ycoord=&74 :REM: &74-&77
1170 start=&350 :REM: screen start address
1180 screen=&355 :REM: screen mode
1190 sheila=&FE00
1200 FOR pass=0 TO 2 STEP 2
1210 P%=mcode
1220 [ OPT pass
1230 LDA #&00
1240 LDX #&07
1250 .initloop
1260 STA xcoord,X \ &70-&77 = #&00
1270 DEX
1280 BPL initloop
1290 LDY screen \ screen mode into Y register
1300 CPY #&06 \ is this mode 6 or 7?
1310 BCS return \ exit if non-graphics mode
1320 CPY #&03 \ is this mode 3?
1330 BNE carryon \ exit if non-graphics mode
1340 .return
1350 RTS \ return to BASIC if non-graphics mode
1360 .carryon
1370 LDA start \ screen start address, low byte
1380 STA ycoord
1390 LDA start+1 \ screen start address, high byte
1400 STA ycoord+1
1410 LSR ycoord+1
1420 ROR ycoord \ start address DIV 2
1430 LSR ycoord+1
1440 ROR ycoord \ start address DIV 4
1450 LSR ycoord+1
1460 ROR ycoord \ start address DIV 8
1470 LDA offsetlow,Y \ trim the offset
1480 CLD \ clear decimal flag
1490 CLC \ prepare for addition
1500 ADC ycoord \ add trim to offset
1510 STA ycoord
1520 LDA #&00
1530 ADC ycoord+1
1540 STA ycoord+1
1550 SEC \ prepare to subtract offset from light pen
\ register
1560 LDX #&11 \ light pen register, low byte
1570 STX sheila \ 6845 address register
1580 LDA sheila+1 \ 6845 data register
1590 SBC ycoord \ subtract offset, low byte
1600 STA ycoord \ low byte - offset
1610 DEX \ X = #&10
1620 STX sheila \ 6845 address register
1630 LDA sheila+1 \ 6845 data register
1640 SBC ycoord+1 \ subtract offset, high byte
1650 STA ycoord+1 \ high byte - offset
1660 .next
1670 ASL ycoord \ shift dividend/quotient left
1680 ROL ycoord+1 \ shift dividend/quotient left
1690 ROL xcoord \ shift bits into partial dividend
1700 LDA xcoord \ load partial dividend
1710 SEC \ prepare for subtraction
1720 SBC width,Y \ subtract divisor
1730 BCC done \ branch if dividend < divisor
1740 INC ycoord \ increment quotient
1750 STA xcoord \ save new partial dividend
1760 .done
1770 DEX \ decrement bit counter
1780 BNE next \ branch for 16 bits
1790 LDA xloop,Y \ prepare for multiplication
1800 TAX \ X=4 modes 0-3, X=5 modes 4-7
1810 .multx
1820 ASL xcoord \ low byte * 2
1830 ROL xcoord+1 \ high byte * 2
1840 DEX \ count number of multiplications
1850 BNE multx \ go back if not finished
1860 LDA xadd,Y \ A=8 modes 0-3, A=16 modes 4-7
1870 CLC \ prepare for addition
1880 ADC xcoord
1890 STA xcoord
1900 LDA #&00
1910 ADC xcoord+1
1920 CMP #&05 \ max value = 4
1930 BCC inrange
1940 LDA #&02 \ dummy value
1950 .inrange
1960 STA xcoord+1
1970 LDX #&05 \ prepare for y coordinate multiplication
1980 .multy
1990 ASL ycoord \ low byte * 2
2000 ROL ycoord+1 \ high byte * 2
2010 DEX \ count number of multiplications
2020 BNE multy \ go back if not finished
2030 SEC \ prepare for subtraction
2040 LDA #&F0 \ low byte of decimal 1008
2050 SBC ycoord \ ycoord-#&F0
2060 STA ycoord
2070 LDA #&03 \ high byte of decimal 1008
2080 SBC ycoord+1 \ (ycoord+1)-#&03
2090 AND #&03 \ max value = 3
2100 STA ycoord+1
2110 RTS \ return to BASIC
2120 .offsetlow
2130 EQUB &04 \ mode0, untrimmed = &06
2140 EQUB &04 \ mode1, untrimmed = &06
2150 EQUB &04 \ mode2, untrimmed = &06
2160 EQUB &00 \ mode3, dummy value
2170 EQUB &03 \ mode4, untrimmed = &04
2180 EQUB &03 \ mode5, untrimmed = &04
2190 .xloop
2200 EQUD &00040404 \ modes 3-0
2210 EQUW &0505 \ modes 5-4
2220 .xadd
2230 EQUD &00080808 \ modes 3-0
2240 EQUW &1010 \ modes 5-4
2250 .width
2260 EQUD &00505050 \ modes 3-0
2270 EQUW &2828 \ modes 5-4
2280 .lastbyte
2290 ]
2300 NEXT
2310 ENDPROC
2320 :
2330 DEFFNswitch
2340 IF (ADVAL(0)AND3)=0 IF !xcoord>16 IF !xcoord<1248 =FALSE
2350 =TRUE
00000000 55 73 69 6e 67 20 61 20 6c 69 67 68 74 20 70 65 |Using a light pe| 00000010 6e 20 77 69 74 68 20 74 68 65 20 42 42 43 20 6d |n with the BBC m| 00000020 69 63 72 6f 63 6f 6d 70 75 74 65 72 20 2d 20 62 |icrocomputer - b| 00000030 79 20 2d 20 47 6f 72 64 6f 6e 20 48 6f 72 73 69 |y - Gordon Horsi| 00000040 6e 67 74 6f 6e 0d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |ngton.----------| 00000050 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------| * 00000080 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 0d 0d 4d 6f 64 |-----------..Mod| 00000090 75 6c 65 20 34 2e 20 55 73 69 6e 67 20 61 20 6c |ule 4. Using a l| 000000a0 69 67 68 74 20 70 65 6e 20 66 6f 72 20 67 72 61 |ight pen for gra| 000000b0 70 68 69 63 73 20 69 6e 70 75 74 0d 2d 2d 2d 2d |phics input.----| 000000c0 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------| * 000000e0 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 0d 0d 0d 54 68 65 |----------...The| 000000f0 20 63 61 6c 63 75 6c 61 74 69 6f 6e 20 6f 66 20 | calculation of | 00000100 67 72 61 70 68 69 63 73 20 63 6f 6f 72 64 69 6e |graphics coordin| 00000110 61 74 65 73 20 69 73 20 76 65 72 79 20 73 69 6d |ates is very sim| 00000120 69 6c 61 72 20 74 6f 20 74 68 65 20 63 61 6c 63 |ilar to the calc| 00000130 75 6c 61 74 69 6f 6e 0d 75 73 65 64 20 69 6e 20 |ulation.used in | 00000140 6d 6f 64 75 6c 65 20 33 20 74 6f 20 64 65 74 65 |module 3 to dete| 00000150 72 6d 69 6e 65 20 74 65 78 74 20 63 6f 6f 72 64 |rmine text coord| 00000160 69 6e 61 74 65 73 20 65 78 63 65 70 74 20 74 68 |inates except th| 00000170 61 74 20 74 68 65 20 66 75 6c 6c 0d 72 65 73 6f |at the full.reso| 00000180 6c 75 74 69 6f 6e 20 6f 66 20 74 68 65 20 6c 69 |lution of the li| 00000190 67 68 74 20 70 65 6e 20 63 61 6e 20 62 65 20 75 |ght pen can be u| 000001a0 73 65 64 20 69 6e 20 74 68 65 20 67 72 61 70 68 |sed in the graph| 000001b0 69 63 73 20 6d 6f 64 65 73 2e 20 41 20 6c 69 67 |ics modes. A lig| 000001c0 68 74 20 70 65 6e 0d 69 73 20 63 61 70 61 62 6c |ht pen.is capabl| 000001d0 65 20 6f 66 20 72 65 73 6f 6c 76 69 6e 67 20 61 |e of resolving a| 000001e0 20 73 69 6e 67 6c 65 20 36 38 34 35 20 43 52 54 | single 6845 CRT| 000001f0 43 20 63 68 61 72 61 63 74 65 72 20 61 6e 64 20 |C character and | 00000200 74 68 65 20 63 61 6c 63 75 6c 61 74 69 6f 6e 0d |the calculation.| 00000210 64 65 6d 6f 6e 73 74 72 61 74 65 64 20 69 6e 20 |demonstrated in | 00000220 74 68 69 73 20 6d 6f 64 75 6c 65 20 77 69 6c 6c |this module will| 00000230 20 72 65 74 75 72 6e 20 74 68 65 20 67 72 61 70 | return the grap| 00000240 68 69 63 73 20 63 6f 6f 72 64 69 6e 61 74 65 73 |hics coordinates| 00000250 20 6f 66 20 74 68 65 0d 6d 69 64 64 6c 65 20 6f | of the.middle o| 00000260 66 20 61 6e 79 20 43 52 54 43 20 63 68 61 72 61 |f any CRTC chara| 00000270 63 74 65 72 20 73 65 65 6e 20 62 79 20 74 68 65 |cter seen by the| 00000280 20 6c 69 67 68 74 20 70 65 6e 2e 20 54 68 69 73 | light pen. This| 00000290 20 63 61 6c 63 75 6c 61 74 69 6f 6e 20 63 61 6e | calculation can| 000002a0 0d 62 65 20 6d 61 64 65 20 69 6e 20 61 6c 6c 20 |.be made in all | 000002b0 74 68 65 20 67 72 61 70 68 69 63 73 20 6d 6f 64 |the graphics mod| 000002c0 65 73 20 62 75 74 20 69 74 20 69 73 20 6e 6f 74 |es but it is not| 000002d0 20 76 65 72 79 20 6d 65 61 6e 69 6e 67 66 75 6c | very meaningful| 000002e0 20 74 6f 0d 63 61 6c 63 75 6c 61 74 65 20 67 72 | to.calculate gr| 000002f0 61 70 68 69 63 73 20 63 6f 6f 72 64 69 6e 61 74 |aphics coordinat| 00000300 65 73 20 69 6e 20 74 68 65 20 6e 6f 6e 2d 67 72 |es in the non-gr| 00000310 61 70 68 69 63 73 20 6d 6f 64 65 73 2e 20 4d 6f |aphics modes. Mo| 00000320 64 65 20 37 20 68 61 73 0d 67 72 61 70 68 69 63 |de 7 has.graphic| 00000330 73 20 6f 66 20 61 20 73 6f 72 74 20 62 75 74 20 |s of a sort but | 00000340 49 20 74 68 69 6e 6b 20 74 68 65 79 20 61 72 65 |I think they are| 00000350 20 62 65 73 74 20 75 6e 64 65 72 73 74 6f 6f 64 | best understood| 00000360 20 61 73 20 61 6e 20 61 6c 74 65 72 6e 61 74 69 | as an alternati| 00000370 76 65 0d 63 68 61 72 61 63 74 65 72 20 73 65 74 |ve.character set| 00000380 20 72 61 74 68 65 72 20 74 68 61 6e 20 61 73 20 | rather than as | 00000390 74 72 75 65 20 67 72 61 70 68 69 63 73 2e 20 49 |true graphics. I| 000003a0 66 20 74 68 65 20 61 6c 67 6f 72 69 74 68 6d 20 |f the algorithm | 000003b0 64 65 73 63 72 69 62 65 64 20 69 6e 0d 74 68 69 |described in.thi| 000003c0 73 20 6d 6f 64 75 6c 65 2c 20 61 6e 64 20 64 65 |s module, and de| 000003d0 6d 6f 6e 73 74 72 61 74 65 64 20 69 6e 20 74 68 |monstrated in th| 000003e0 65 20 70 72 6f 67 72 61 6d 20 47 52 41 50 48 49 |e program GRAPHI| 000003f0 43 2c 20 69 73 20 75 73 65 64 20 69 6e 20 61 0d |C, is used in a.| 00000400 6e 6f 6e 2d 67 72 61 70 68 69 63 73 20 6d 6f 64 |non-graphics mod| 00000410 65 20 69 74 20 77 69 6c 6c 20 67 69 76 65 20 61 |e it will give a| 00000420 20 6d 69 73 6c 65 61 64 69 6e 67 20 61 6e 73 77 | misleading answ| 00000430 65 72 2e 20 49 20 64 6f 6e 27 74 20 74 68 69 73 |er. I don't this| 00000440 20 69 73 20 72 65 61 6c 6c 79 0d 61 20 70 72 6f | is really.a pro| 00000450 62 6c 65 6d 20 62 65 63 61 75 73 65 20 74 68 65 |blem because the| 00000460 72 65 20 63 61 6e 20 6e 6f 74 20 62 65 20 61 6e |re can not be an| 00000470 79 20 63 6f 72 72 65 63 74 20 61 6e 73 77 65 72 |y correct answer| 00000480 20 66 6f 72 20 67 72 61 70 68 69 63 73 0d 63 6f | for graphics.co| 00000490 6f 72 64 69 6e 61 74 65 73 20 69 6e 20 61 20 6e |ordinates in a n| 000004a0 6f 6e 2d 67 72 61 70 68 69 63 73 20 73 63 72 65 |on-graphics scre| 000004b0 65 6e 20 6d 6f 64 65 2e 0d 0d 54 68 65 20 74 61 |en mode...The ta| 000004c0 62 6c 65 20 69 6e 20 66 69 67 75 72 65 20 31 20 |ble in figure 1 | 000004d0 73 68 6f 77 73 20 74 68 65 20 76 61 6c 75 65 73 |shows the values| 000004e0 20 6f 66 20 74 68 65 20 76 61 72 69 61 62 6c 65 | of the variable| 000004f0 73 20 75 73 65 64 20 69 6e 20 74 68 65 0d 63 61 |s used in the.ca| 00000500 6c 63 75 6c 61 74 69 6f 6e 20 6f 66 20 67 72 61 |lculation of gra| 00000510 70 68 69 63 73 20 63 6f 6f 72 64 69 6e 61 74 65 |phics coordinate| 00000520 73 2e 20 54 68 65 20 76 61 6c 75 65 73 20 61 73 |s. The values as| 00000530 73 69 67 6e 65 64 20 74 6f 20 74 68 65 20 73 63 |signed to the sc| 00000540 72 65 65 6e 0d 73 74 61 72 74 20 61 64 64 72 65 |reen.start addre| 00000550 73 73 20 69 6e 20 74 68 69 73 20 74 61 62 6c 65 |ss in this table| 00000560 20 63 61 6e 20 6f 6e 6c 79 20 62 65 20 75 73 65 | can only be use| 00000570 64 20 69 66 20 74 68 65 20 73 63 72 65 65 6e 20 |d if the screen | 00000580 68 61 73 20 6e 6f 74 20 62 65 65 6e 0d 73 63 72 |has not been.scr| 00000590 6f 6c 6c 65 64 2e 20 49 66 20 74 68 65 20 73 63 |olled. If the sc| 000005a0 72 65 65 6e 20 69 73 20 73 63 72 6f 6c 6c 65 64 |reen is scrolled| 000005b0 20 74 68 65 20 73 74 61 72 74 20 61 64 64 72 65 | the start addre| 000005c0 73 73 20 63 68 61 6e 67 65 73 20 66 72 6f 6d 20 |ss changes from | 000005d0 74 68 65 0d 76 61 6c 75 65 73 20 73 68 6f 77 6e |the.values shown| 000005e0 20 69 6e 20 66 69 67 75 72 65 20 31 2e 20 54 68 | in figure 1. Th| 000005f0 65 20 63 75 72 72 65 6e 74 20 73 63 72 65 65 6e |e current screen| 00000600 20 73 74 61 72 74 20 61 64 64 72 65 73 73 20 73 | start address s| 00000610 68 6f 75 6c 64 0d 74 68 65 72 65 66 6f 72 65 20 |hould.therefore | 00000620 62 65 20 72 65 61 64 20 66 72 6f 6d 20 26 33 35 |be read from &35| 00000630 30 20 28 6c 6f 77 20 62 79 74 65 29 20 61 6e 64 |0 (low byte) and| 00000640 20 26 33 35 31 20 28 68 69 67 68 20 62 79 74 65 | &351 (high byte| 00000650 29 2e 0d 0d 0d 20 20 20 20 20 20 20 20 20 4d 6f |).... Mo| 00000660 64 65 20 20 73 74 61 72 74 20 61 64 64 72 20 20 |de start addr | 00000670 74 72 69 6d 20 20 20 20 77 69 64 74 68 20 20 20 |trim width | 00000680 72 65 73 6f 6c 75 74 69 6f 6e 0d 20 20 20 20 20 |resolution. | 00000690 20 20 20 2d 2d 2d 2d 2d 2b 2d 2d 2d 2d 2d 2d 2d | -----+-------| 000006a0 2d 2d 2d 2d 2b 2d 2d 2d 2d 2d 2d 2d 2b 2d 2d 2d |----+-------+---| 000006b0 2d 2d 2d 2d 2b 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----+-----------| 000006c0 2d 0d 20 20 20 20 20 20 20 20 20 20 30 20 20 7c |-. 0 || 000006d0 20 20 20 26 33 30 30 30 20 20 20 7c 20 20 26 30 | &3000 | &0| 000006e0 36 20 20 7c 20 20 26 35 30 20 20 7c 20 38 30 20 |6 | &50 | 80 | 000006f0 78 20 33 32 0d 20 20 20 20 20 20 20 20 20 20 31 |x 32. 1| 00000700 20 20 7c 20 20 20 26 33 30 30 30 20 20 20 7c 20 | | &3000 | | 00000710 20 26 30 36 20 20 7c 20 20 26 35 30 20 20 7c 20 | &06 | &50 | | 00000720 38 30 20 78 20 33 32 0d 20 20 20 20 20 20 20 20 |80 x 32. | 00000730 20 20 32 20 20 7c 20 20 20 26 33 30 30 30 20 20 | 2 | &3000 | 00000740 20 7c 20 20 26 30 36 20 20 7c 20 20 26 35 30 20 | | &06 | &50 | 00000750 20 7c 20 38 30 20 78 20 33 32 0d 20 20 20 20 20 | | 80 x 32. | 00000760 20 20 20 20 20 34 20 20 7c 20 20 20 26 35 38 30 | 4 | &580| 00000770 30 20 20 20 7c 20 20 26 30 34 20 20 7c 20 20 26 |0 | &04 | &| 00000780 32 38 20 20 7c 20 34 30 20 78 20 33 32 0d 20 20 |28 | 40 x 32. | 00000790 20 20 20 20 20 20 20 20 35 20 20 7c 20 20 20 26 | 5 | &| 000007a0 35 38 30 30 20 20 20 7c 20 20 26 30 34 20 20 7c |5800 | &04 || 000007b0 20 20 26 32 38 20 20 7c 20 34 30 20 78 20 33 32 | &28 | 40 x 32| 000007c0 0d 20 20 20 20 20 20 20 20 2d 2d 2d 2d 2d 2b 2d |. -----+-| 000007d0 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2b 2d 2d 2d 2d 2d |----------+-----| 000007e0 2d 2d 2b 2d 2d 2d 2d 2d 2d 2d 2b 2d 2d 2d 2d 2d |--+-------+-----| 000007f0 2d 2d 2d 2d 2d 2d 2d 0d 0d 46 69 67 75 72 65 20 |-------..Figure | 00000800 31 2e 20 54 68 65 20 73 74 61 72 74 20 61 64 64 |1. The start add| 00000810 72 65 73 73 2c 20 74 72 69 6d 2c 20 61 6e 64 20 |ress, trim, and | 00000820 77 69 64 74 68 20 66 6f 72 20 65 61 63 68 20 67 |width for each g| 00000830 72 61 70 68 69 63 73 20 6d 6f 64 65 0d 2d 2d 2d |raphics mode.---| 00000840 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------| * 00000880 0d 0d 0d 54 68 65 20 66 69 72 73 74 20 73 74 61 |...The first sta| 00000890 67 65 20 69 6e 20 63 61 6c 63 75 6c 61 74 69 6e |ge in calculatin| 000008a0 67 20 74 68 65 20 6c 69 67 68 74 20 70 65 6e 20 |g the light pen | 000008b0 70 6f 73 69 74 69 6f 6e 20 69 73 20 74 6f 20 64 |position is to d| 000008c0 65 74 65 72 6d 69 6e 65 20 74 68 65 0d 76 61 6c |etermine the.val| 000008d0 75 65 20 6f 66 20 74 68 65 20 6f 66 66 73 65 74 |ue of the offset| 000008e0 2e 20 54 68 65 20 6f 66 66 73 65 74 20 69 6e 20 |. The offset in | 000008f0 61 6c 6c 20 67 72 61 70 68 69 63 73 20 6d 6f 64 |all graphics mod| 00000900 65 73 20 69 73 20 67 69 76 65 6e 20 62 79 3a 0d |es is given by:.| 00000910 0d 20 20 6f 66 66 73 65 74 20 3d 20 74 72 69 6d |. offset = trim| 00000920 20 2b 20 28 73 63 72 65 65 6e 20 73 74 61 72 74 | + (screen start| 00000930 20 61 64 64 72 65 73 73 20 44 49 56 20 38 29 0d | address DIV 8).| 00000940 0d 54 68 65 20 43 52 43 54 20 58 20 61 6e 64 20 |.The CRCT X and | 00000950 59 20 63 6f 6f 72 64 69 6e 61 74 65 73 20 63 61 |Y coordinates ca| 00000960 6e 20 74 68 65 6e 20 62 65 20 63 61 6c 63 75 6c |n then be calcul| 00000970 61 74 65 64 20 75 73 69 6e 67 20 74 68 65 20 61 |ated using the a| 00000980 70 70 72 6f 70 72 69 61 74 65 0d 76 61 6c 75 65 |ppropriate.value| 00000990 20 6f 66 20 6f 66 66 73 65 74 2e 0d 0d 20 20 59 | of offset... Y| 000009a0 20 3d 20 28 6c 69 67 68 74 20 70 65 6e 20 72 65 | = (light pen re| 000009b0 67 69 73 74 65 72 20 2d 20 6f 66 66 73 65 74 29 |gister - offset)| 000009c0 20 44 49 56 20 77 69 64 74 68 0d 0d 20 20 58 20 | DIV width.. X | 000009d0 3d 20 28 6c 69 67 68 74 20 70 65 6e 20 72 65 67 |= (light pen reg| 000009e0 69 73 74 65 72 20 2d 20 6f 66 66 73 65 74 29 20 |ister - offset) | 000009f0 4d 4f 44 20 77 69 64 74 68 0d 0d 41 20 43 52 43 |MOD width..A CRC| 00000a00 54 20 59 20 63 6f 6f 72 64 69 6e 61 74 65 20 63 |T Y coordinate c| 00000a10 61 6e 20 62 65 20 63 6f 6e 76 65 72 74 65 64 20 |an be converted | 00000a20 69 6e 74 6f 20 61 20 67 72 61 70 68 69 63 73 20 |into a graphics | 00000a30 59 20 63 6f 6f 72 64 69 6e 61 74 65 20 62 79 0d |Y coordinate by.| 00000a40 6d 75 6c 74 69 70 6c 79 69 6e 67 20 69 74 20 62 |multiplying it b| 00000a50 79 20 33 32 20 61 6e 64 20 74 68 65 6e 20 73 75 |y 32 and then su| 00000a60 62 74 72 61 63 74 69 6e 67 20 74 68 65 20 70 72 |btracting the pr| 00000a70 6f 64 75 63 74 20 66 72 6f 6d 20 31 30 30 38 2e |oduct from 1008.| 00000a80 0d 0d 41 20 43 52 43 54 20 58 20 63 6f 6f 72 64 |..A CRCT X coord| 00000a90 69 6e 61 74 65 20 63 61 6e 20 62 65 20 63 6f 6e |inate can be con| 00000aa0 76 65 72 74 65 64 20 69 6e 74 6f 20 61 20 67 72 |verted into a gr| 00000ab0 61 70 68 69 63 73 20 58 20 63 6f 6f 72 64 69 6e |aphics X coordin| 00000ac0 61 74 65 20 69 6e 20 6d 6f 64 65 73 0d 30 20 74 |ate in modes.0 t| 00000ad0 6f 20 32 20 62 79 20 6d 75 6c 74 69 70 6c 79 69 |o 2 by multiplyi| 00000ae0 6e 67 20 69 74 20 62 79 20 38 20 61 6e 64 20 74 |ng it by 8 and t| 00000af0 68 65 6e 20 61 64 64 69 6e 67 20 38 2e 20 49 6e |hen adding 8. In| 00000b00 20 6d 6f 64 65 73 20 34 20 61 6e 64 20 35 20 61 | modes 4 and 5 a| 00000b10 20 43 52 43 54 20 58 0d 63 6f 6f 72 64 69 6e 61 | CRCT X.coordina| 00000b20 74 65 20 63 61 6e 20 62 65 20 63 6f 6e 76 65 72 |te can be conver| 00000b30 74 65 64 20 69 6e 74 6f 20 61 20 67 72 61 70 68 |ted into a graph| 00000b40 69 63 73 20 63 6f 6f 72 64 69 6e 61 74 65 20 62 |ics coordinate b| 00000b50 79 20 6d 75 6c 74 69 70 6c 79 69 6e 67 20 69 74 |y multiplying it| 00000b60 0d 62 79 20 31 36 20 61 6e 64 20 74 68 65 6e 20 |.by 16 and then | 00000b70 61 64 64 69 6e 67 20 31 36 2e 0d 0d 54 68 65 20 |adding 16...The | 00000b80 76 61 6c 75 65 73 20 6f 66 20 74 72 69 6d 20 61 |values of trim a| 00000b90 6e 64 20 77 69 64 74 68 20 75 73 65 64 20 69 6e |nd width used in| 00000ba0 20 74 68 65 73 65 20 63 61 6c 63 75 6c 61 74 69 | these calculati| 00000bb0 6f 6e 73 20 61 72 65 20 74 68 6f 73 65 0d 61 70 |ons are those.ap| 00000bc0 70 72 6f 70 72 69 61 74 65 20 74 6f 20 74 68 65 |propriate to the| 00000bd0 20 73 63 72 65 65 6e 20 6d 6f 64 65 20 69 6e 20 | screen mode in | 00000be0 75 73 65 20 61 74 20 74 68 65 20 74 69 6d 65 2e |use at the time.| 00000bf0 20 54 68 65 20 73 63 72 65 65 6e 20 6d 6f 64 65 | The screen mode| 00000c00 0d 28 69 67 6e 6f 72 69 6e 67 20 73 68 61 64 6f |.(ignoring shado| 00000c10 77 29 20 63 61 6e 20 62 65 20 72 65 61 64 20 66 |w) can be read f| 00000c20 72 6f 6d 20 26 33 35 35 2e 20 54 68 65 20 76 61 |rom &355. The va| 00000c30 6c 75 65 73 20 75 73 65 64 20 66 6f 72 20 74 72 |lues used for tr| 00000c40 69 6d 20 77 69 6c 6c 2c 20 61 73 0d 74 68 65 20 |im will, as.the | 00000c50 6e 61 6d 65 20 73 75 67 67 65 73 74 73 2c 20 6e |name suggests, n| 00000c60 65 65 64 20 74 6f 20 62 65 20 74 72 69 6d 6d 65 |eed to be trimme| 00000c70 64 20 61 73 20 64 65 73 63 72 69 62 65 64 20 69 |d as described i| 00000c80 6e 20 74 68 65 20 65 61 72 6c 69 65 72 20 6d 6f |n the earlier mo| 00000c90 64 75 6c 65 73 2e 0d 54 68 65 20 76 61 6c 75 65 |dules..The value| 00000ca0 73 20 6f 66 20 74 72 69 6d 20 75 73 65 64 20 69 |s of trim used i| 00000cb0 6e 20 74 68 65 20 64 65 6d 6f 6e 73 74 72 61 74 |n the demonstrat| 00000cc0 69 6f 6e 20 70 72 6f 67 72 61 6d 20 47 52 41 50 |ion program GRAP| 00000cd0 48 49 43 20 61 72 65 20 74 68 6f 73 65 20 49 0d |HIC are those I.| 00000ce0 66 6f 75 6e 64 20 74 6f 20 62 65 20 6d 6f 73 74 |found to be most| 00000cf0 20 73 75 69 74 61 62 6c 65 20 66 6f 72 20 6d 79 | suitable for my| 00000d00 20 6c 69 67 68 74 20 70 65 6e 2e 20 59 6f 75 20 | light pen. You | 00000d10 6d 69 67 68 74 20 6c 69 6b 65 20 74 6f 20 65 64 |might like to ed| 00000d20 69 74 20 74 68 65 0d 70 72 6f 67 72 61 6d 20 74 |it the.program t| 00000d30 6f 20 75 73 65 20 74 68 65 20 76 61 6c 75 65 73 |o use the values| 00000d40 20 62 65 73 74 20 73 75 69 74 65 64 20 74 6f 20 | best suited to | 00000d50 79 6f 75 72 20 6c 69 67 68 74 20 70 65 6e 20 62 |your light pen b| 00000d60 75 74 20 79 6f 75 20 63 61 6e 20 61 6c 73 6f 0d |ut you can also.| 00000d70 74 72 69 6d 20 74 68 65 20 76 61 6c 75 65 73 20 |trim the values | 00000d80 49 20 68 61 76 65 20 75 73 65 64 20 77 69 74 68 |I have used with| 00000d90 20 74 68 65 20 6c 65 66 74 20 61 6e 64 20 72 69 | the left and ri| 00000da0 67 68 74 20 63 75 72 73 6f 72 20 6b 65 79 73 20 |ght cursor keys | 00000db0 77 68 65 6e 20 74 68 65 0d 70 72 6f 67 72 61 6d |when the.program| 00000dc0 20 69 73 20 72 75 6e 6e 69 6e 67 2e 20 54 68 65 | is running. The| 00000dd0 20 6c 61 62 65 6c 20 6f 66 66 73 65 74 6c 6f 77 | label offsetlow| 00000de0 20 69 73 20 75 73 65 64 20 66 6f 72 20 74 68 65 | is used for the| 00000df0 20 74 61 62 6c 65 20 6f 66 20 76 61 6c 75 65 73 | table of values| 00000e00 0d 61 73 73 69 67 6e 65 64 20 74 6f 20 74 72 69 |.assigned to tri| 00000e10 6d 2e 0d 0d 54 68 65 20 72 61 6e 67 65 20 6f 66 |m...The range of| 00000e20 20 74 68 65 20 58 20 61 6e 64 20 59 20 63 6f 6f | the X and Y coo| 00000e30 72 64 69 6e 61 74 65 73 20 6d 61 64 65 20 61 76 |rdinates made av| 00000e40 61 69 6c 61 62 6c 65 20 62 79 20 74 68 69 73 20 |ailable by this | 00000e50 61 6c 67 6f 72 69 74 68 6d 20 69 73 0d 69 6e 64 |algorithm is.ind| 00000e60 65 70 65 6e 64 61 6e 74 20 6f 66 20 74 68 65 20 |ependant of the | 00000e70 73 63 72 65 65 6e 20 6d 6f 64 65 2e 20 54 68 65 |screen mode. The| 00000e80 20 70 6f 69 6e 74 20 30 2c 30 20 69 73 20 61 6c | point 0,0 is al| 00000e90 77 61 79 73 20 69 6e 20 74 68 65 20 62 6f 74 74 |ways in the bott| 00000ea0 6f 6d 20 6c 65 66 74 0d 6f 66 20 74 68 65 20 73 |om left.of the s| 00000eb0 63 72 65 65 6e 20 61 6e 64 20 31 32 37 39 2c 31 |creen and 1279,1| 00000ec0 30 32 33 20 69 73 20 61 6c 77 61 79 73 20 69 6e |023 is always in| 00000ed0 20 74 68 65 20 74 6f 70 20 72 69 67 68 74 20 62 | the top right b| 00000ee0 75 74 2c 20 62 65 63 61 75 73 65 20 74 68 65 0d |ut, because the.| 00000ef0 63 6f 6f 72 64 69 6e 61 74 65 73 20 63 6f 72 72 |coordinates corr| 00000f00 65 73 70 6f 6e 64 20 77 69 74 68 20 74 68 65 20 |espond with the | 00000f10 63 65 6e 74 72 65 20 6f 66 20 43 52 54 43 20 63 |centre of CRTC c| 00000f20 68 61 72 61 63 74 65 72 73 2c 20 74 68 65 20 72 |haracters, the r| 00000f30 61 6e 67 65 0d 61 76 61 69 6c 61 62 6c 65 20 69 |ange.available i| 00000f40 73 20 66 72 6f 6d 20 38 2c 38 20 74 6f 20 31 32 |s from 8,8 to 12| 00000f50 37 31 2c 31 30 31 35 20 69 6e 20 6d 6f 64 65 73 |71,1015 in modes| 00000f60 20 30 2c 20 31 20 61 6e 64 20 32 2c 20 61 6e 64 | 0, 1 and 2, and| 00000f70 20 66 72 6f 6d 20 31 36 2c 31 36 20 74 6f 0d 31 | from 16,16 to.1| 00000f80 32 36 33 2c 31 30 30 38 20 69 6e 20 6d 6f 64 65 |263,1008 in mode| 00000f90 73 20 34 20 61 6e 64 20 35 2e 20 41 20 6d 61 78 |s 4 and 5. A max| 00000fa0 69 6d 75 6d 20 6f 66 20 74 77 6f 20 62 79 74 65 |imum of two byte| 00000fb0 73 20 61 72 65 20 72 65 71 75 69 72 65 64 20 74 |s are required t| 00000fc0 6f 20 73 74 6f 72 65 0d 65 61 63 68 20 63 6f 6f |o store.each coo| 00000fd0 72 64 69 6e 61 74 65 20 62 75 74 20 74 68 65 20 |rdinate but the | 00000fe0 6d 61 63 68 69 6e 65 20 63 6f 64 65 20 72 6f 75 |machine code rou| 00000ff0 74 69 6e 65 20 69 6e 20 74 68 65 20 70 72 6f 67 |tine in the prog| 00001000 72 61 6d 20 47 52 41 50 48 49 43 20 75 73 65 73 |ram GRAPHIC uses| 00001010 20 34 0d 62 79 74 65 73 20 70 65 72 20 63 6f 6f | 4.bytes per coo| 00001020 72 64 69 6e 61 74 65 20 73 6f 20 74 68 61 74 20 |rdinate so that | 00001030 74 68 65 20 63 6f 6f 72 64 69 6e 61 74 65 73 20 |the coordinates | 00001040 63 61 6e 20 62 65 20 72 65 61 64 20 75 73 69 6e |can be read usin| 00001050 67 20 74 68 65 20 42 41 53 49 43 20 21 0d 69 6e |g the BASIC !.in| 00001060 64 69 72 65 63 74 69 6f 6e 20 6f 70 65 72 61 74 |direction operat| 00001070 6f 72 2e 20 54 68 65 20 72 6f 75 74 69 6e 65 20 |or. The routine | 00001080 61 6c 77 61 79 73 20 72 65 74 75 72 6e 73 20 74 |always returns t| 00001090 68 65 20 63 6f 6f 72 64 69 6e 61 74 65 73 20 30 |he coordinates 0| 000010a0 2c 30 20 69 66 20 69 74 0d 69 73 20 63 61 6c 6c |,0 if it.is call| 000010b0 65 64 20 69 6e 20 61 20 6e 6f 6e 2d 67 72 61 70 |ed in a non-grap| 000010c0 68 69 63 73 20 6d 6f 64 65 2e 0d 0d 54 68 65 20 |hics mode...The | 000010d0 6d 61 63 68 69 6e 65 20 63 6f 64 65 20 72 6f 75 |machine code rou| 000010e0 74 69 6e 65 20 69 6e 20 74 68 65 20 64 65 6d 6f |tine in the demo| 000010f0 6e 73 74 72 61 74 69 6f 6e 20 70 72 6f 67 72 61 |nstration progra| 00001100 6d 20 63 68 65 63 6b 73 20 74 68 61 74 20 74 68 |m checks that th| 00001110 65 0d 63 6f 6f 72 64 69 6e 61 74 65 73 20 69 74 |e.coordinates it| 00001120 20 70 72 6f 64 75 63 65 73 20 61 72 65 20 77 69 | produces are wi| 00001130 74 68 69 6e 20 74 68 65 20 65 78 70 65 63 74 65 |thin the expecte| 00001140 64 20 72 61 6e 67 65 2e 20 54 68 69 73 20 69 73 |d range. This is| 00001150 20 61 20 67 6f 6f 64 20 69 64 65 61 0d 77 69 74 | a good idea.wit| 00001160 68 20 6e 6f 6e 2d 69 6e 74 65 72 72 75 70 74 20 |h non-interrupt | 00001170 6c 69 67 68 74 20 70 65 6e 20 64 72 69 76 65 72 |light pen driver| 00001180 73 20 62 65 63 61 75 73 65 2c 20 69 66 20 74 68 |s because, if th| 00001190 65 20 70 65 6e 20 68 61 73 20 6e 6f 74 20 62 65 |e pen has not be| 000011a0 65 6e 0d 75 73 65 64 2c 20 74 68 65 20 61 6c 67 |en.used, the alg| 000011b0 6f 72 69 74 68 6d 20 67 69 76 65 73 20 61 20 76 |orithm gives a v| 000011c0 65 72 79 20 6d 69 73 6c 65 61 64 69 6e 67 20 61 |ery misleading a| 000011d0 6e 73 77 65 72 2e 20 54 68 69 73 20 69 73 20 6e |nswer. This is n| 000011e0 6f 74 20 61 20 70 72 6f 62 6c 65 6d 0d 74 68 61 |ot a problem.tha| 000011f0 74 20 63 61 6e 20 6f 63 63 75 72 20 77 69 74 68 |t can occur with| 00001200 20 69 6e 74 65 72 72 75 70 74 20 64 72 69 76 65 | interrupt drive| 00001210 6e 20 73 6f 66 74 77 61 72 65 20 62 65 63 61 75 |n software becau| 00001220 73 65 2c 20 62 79 20 64 65 66 69 6e 69 74 69 6f |se, by definitio| 00001230 6e 2c 20 74 68 65 0d 6c 69 67 68 74 20 70 65 6e |n, the.light pen| 00001240 20 6d 75 73 74 20 62 65 20 75 73 65 64 20 74 6f | must be used to| 00001250 20 67 65 6e 65 72 61 74 65 20 74 68 65 20 6c 69 | generate the li| 00001260 67 68 74 20 70 65 6e 20 69 6e 74 65 72 72 75 70 |ght pen interrup| 00001270 74 2e 0d 0d 54 68 65 20 6d 61 78 69 6d 75 6d 20 |t...The maximum | 00001280 72 65 73 6f 6c 75 74 69 6f 6e 20 6f 66 20 74 68 |resolution of th| 00001290 65 20 6c 69 67 68 74 20 70 65 6e 20 67 72 61 70 |e light pen grap| 000012a0 68 69 63 73 20 63 6f 6f 72 64 69 6e 61 74 65 73 |hics coordinates| 000012b0 20 69 73 20 38 30 78 33 32 20 69 6e 0d 6d 6f 64 | is 80x32 in.mod| 000012c0 65 73 20 30 2c 20 31 20 61 6e 64 20 32 2c 20 62 |es 0, 1 and 2, b| 000012d0 75 74 20 61 20 72 61 74 68 65 72 20 63 68 75 6e |ut a rather chun| 000012e0 6b 79 20 34 30 78 33 32 20 69 6e 20 6d 6f 64 65 |ky 40x32 in mode| 000012f0 73 20 34 20 61 6e 64 20 35 20 2d 20 61 6e 64 0d |s 4 and 5 - and.| 00001300 64 65 73 63 72 69 62 69 6e 67 20 74 68 69 73 20 |describing this | 00001310 61 73 20 63 68 75 6e 6b 79 20 69 73 20 62 65 69 |as chunky is bei| 00001320 6e 67 20 71 75 69 74 65 20 67 65 6e 65 72 6f 75 |ng quite generou| 00001330 73 2e 20 49 66 20 79 6f 75 20 75 73 65 20 61 20 |s. If you use a | 00001340 6c 69 67 68 74 20 70 65 6e 0d 74 6f 20 64 72 61 |light pen.to dra| 00001350 77 20 6f 6e 20 61 20 67 72 61 70 68 69 63 73 20 |w on a graphics | 00001360 73 63 72 65 65 6e 20 74 68 69 73 20 70 6f 6f 72 |screen this poor| 00001370 20 72 65 73 6f 6c 75 74 69 6f 6e 20 67 69 76 65 | resolution give| 00001380 73 20 61 20 71 75 69 74 65 20 73 68 61 6b 65 79 |s a quite shakey| 00001390 0d 6c 6f 6f 6b 69 6e 67 20 6c 69 6e 65 20 64 72 |.looking line dr| 000013a0 61 77 69 6e 67 2c 20 65 73 70 65 63 69 61 6c 6c |awing, especiall| 000013b0 79 20 77 69 74 68 20 64 69 61 67 6f 6e 61 6c 20 |y with diagonal | 000013c0 6c 69 6e 65 73 2e 20 49 6e 20 73 70 69 74 65 20 |lines. In spite | 000013d0 6f 66 20 74 68 69 73 0d 61 70 70 61 72 65 6e 74 |of this.apparent| 000013e0 20 70 72 6f 62 6c 65 6d 20 69 74 20 69 73 20 70 | problem it is p| 000013f0 6f 73 73 69 62 6c 65 20 74 6f 20 70 72 6f 64 75 |ossible to produ| 00001400 63 65 20 76 65 72 79 20 73 6d 6f 6f 74 68 20 6c |ce very smooth l| 00001410 69 6e 65 73 20 61 6e 64 20 74 6f 20 64 72 61 77 |ines and to draw| 00001420 0d 77 69 74 68 20 61 6e 20 61 63 63 65 70 74 61 |.with an accepta| 00001430 62 6c 65 20 6c 65 76 65 6c 20 6f 66 20 61 63 63 |ble level of acc| 00001440 75 72 61 63 79 20 66 6f 72 20 66 72 65 65 68 61 |uracy for freeha| 00001450 6e 64 20 77 6f 72 6b 2e 20 49 66 20 79 6f 75 20 |nd work. If you | 00001460 77 61 6e 74 20 74 6f 20 75 73 65 0d 79 6f 75 72 |want to use.your| 00001470 20 63 6f 6d 70 75 74 65 72 20 66 6f 72 20 76 65 | computer for ve| 00001480 72 79 20 61 63 63 75 72 61 74 65 20 64 72 61 77 |ry accurate draw| 00001490 69 6e 67 20 74 68 65 6e 20 79 6f 75 20 73 68 6f |ing then you sho| 000014a0 75 6c 64 20 75 73 65 20 61 20 6d 6f 75 73 65 20 |uld use a mouse | 000014b0 61 73 20 61 6e 0d 69 6e 70 75 74 20 64 65 76 69 |as an.input devi| 000014c0 63 65 20 61 6e 64 20 6e 6f 74 20 61 20 6c 69 67 |ce and not a lig| 000014d0 68 74 20 70 65 6e 2e 0d 0d 53 6d 6f 6f 74 68 20 |ht pen...Smooth | 000014e0 6c 69 6e 65 20 64 72 61 77 69 6e 67 20 77 69 74 |line drawing wit| 000014f0 68 20 61 20 6c 69 67 68 74 20 70 65 6e 20 63 61 |h a light pen ca| 00001500 6e 20 62 65 20 61 63 68 69 65 76 65 64 20 62 79 |n be achieved by| 00001510 20 61 6c 6c 6f 77 69 6e 67 20 74 68 65 20 6c 69 | allowing the li| 00001520 6e 65 0d 62 65 69 6e 67 20 64 72 61 77 6e 20 74 |ne.being drawn t| 00001530 6f 20 6c 61 67 20 62 65 68 69 6e 64 20 74 68 65 |o lag behind the| 00001540 20 63 75 72 72 65 6e 74 20 6c 69 67 68 74 20 70 | current light p| 00001550 65 6e 20 70 6f 73 69 74 69 6f 6e 20 62 75 74 20 |en position but | 00001560 74 6f 20 61 6c 77 61 79 73 0d 61 70 70 72 6f 61 |to always.approa| 00001570 63 68 20 74 68 65 20 63 75 72 72 65 6e 74 20 70 |ch the current p| 00001580 6f 73 69 74 69 6f 6e 20 6f 66 20 74 68 65 20 70 |osition of the p| 00001590 65 6e 2e 20 54 68 69 73 20 69 73 20 61 63 68 69 |en. This is achi| 000015a0 65 76 65 64 20 62 79 20 73 74 6f 72 69 6e 67 20 |eved by storing | 000015b0 74 68 65 0d 63 6f 6f 72 64 69 6e 61 74 65 73 20 |the.coordinates | 000015c0 6f 66 20 74 68 65 20 6c 61 73 74 20 70 6c 6f 74 |of the last plot| 000015d0 74 65 64 20 70 6f 73 69 74 69 6f 6e 20 61 6e 64 |ted position and| 000015e0 20 63 61 6c 63 75 6c 61 74 69 6e 67 20 74 68 65 | calculating the| 000015f0 20 6e 65 78 74 20 70 6f 73 69 74 69 6f 6e 0d 74 | next position.t| 00001600 6f 20 62 65 20 70 6c 6f 74 74 65 64 20 61 73 20 |o be plotted as | 00001610 61 20 66 72 61 63 74 69 6f 6e 20 6f 66 20 74 68 |a fraction of th| 00001620 65 20 64 69 66 66 65 72 65 6e 63 65 20 62 65 74 |e difference bet| 00001630 77 65 65 6e 20 74 68 65 20 6c 61 73 74 20 70 6c |ween the last pl| 00001640 6f 74 74 65 64 0d 70 6f 73 69 74 69 6f 6e 20 61 |otted.position a| 00001650 6e 64 20 74 68 65 20 63 75 72 72 65 6e 74 20 70 |nd the current p| 00001660 6f 73 69 74 69 6f 6e 20 6f 66 20 74 68 65 20 70 |osition of the p| 00001670 65 6e 2e 20 54 68 69 73 20 69 73 20 6d 75 63 68 |en. 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The amm| 000017e0 6f 75 6e 74 20 6f 66 20 6c 61 67 2c 20 61 6e 64 |ount of lag, and| 000017f0 20 74 68 65 0d 72 65 73 75 6c 74 61 6e 74 20 73 | the.resultant s| 00001800 6d 6f 6f 74 68 6e 65 73 73 2c 20 64 65 70 65 6e |moothness, depen| 00001810 64 73 20 6f 6e 20 74 68 65 20 73 69 7a 65 20 6f |ds on the size o| 00001820 66 20 74 68 65 20 42 41 53 49 43 20 76 61 72 69 |f the BASIC vari| 00001830 61 62 6c 65 20 64 69 76 69 73 6f 72 0d 28 6c 69 |able divisor.(li| 00001840 6e 65 20 31 30 30 29 2e 20 54 68 65 20 6c 61 72 |ne 100). The lar| 00001850 67 65 72 20 74 68 65 20 76 61 6c 75 65 20 6f 66 |ger the value of| 00001860 20 74 68 65 20 64 69 76 69 73 6f 72 20 28 75 73 | the divisor (us| 00001870 65 64 20 69 6e 20 6c 69 6e 65 73 20 32 31 30 20 |ed in lines 210 | 00001880 61 6e 64 0d 32 32 30 29 20 74 68 65 20 67 72 65 |and.220) the gre| 00001890 61 74 65 72 20 74 68 65 20 6c 61 67 20 61 6e 64 |ater the lag and| 000018a0 20 74 68 65 20 73 6d 6f 6f 74 68 65 72 20 74 68 | the smoother th| 000018b0 65 20 6c 69 6e 65 2e 20 54 68 65 20 64 69 76 69 |e line. The divi| 000018c0 73 6f 72 20 6d 75 73 74 20 62 65 0d 74 68 65 20 |sor must be.the | 000018d0 73 61 6d 65 20 66 6f 72 20 62 6f 74 68 20 58 20 |same for both X | 000018e0 61 6e 64 20 59 20 6f 74 68 65 72 77 69 73 65 20 |and Y otherwise | 000018f0 63 69 72 63 6c 65 73 20 77 69 6c 6c 20 62 65 20 |circles will be | 00001900 64 72 61 77 6e 20 61 73 20 65 6c 69 70 73 65 73 |drawn as elipses| 00001910 2e 0d 0d 43 68 61 69 6e 20 74 68 65 20 70 72 6f |...Chain the pro| 00001920 67 72 61 6d 20 47 52 41 50 48 49 43 20 77 68 69 |gram GRAPHIC whi| 00001930 63 68 20 77 69 6c 6c 20 61 6c 6c 6f 77 20 79 6f |ch will allow yo| 00001940 75 20 74 6f 20 64 72 61 77 20 77 69 74 68 20 61 |u to draw with a| 00001950 20 6c 69 67 68 74 20 70 65 6e 20 69 6e 0d 61 6e | light pen in.an| 00001960 79 20 67 72 61 70 68 69 63 73 20 73 63 72 65 65 |y graphics scree| 00001970 6e 20 6d 6f 64 65 2e 20 54 68 65 20 73 63 72 65 |n mode. The scre| 00001980 65 6e 20 6d 6f 64 65 73 20 63 61 6e 20 62 65 20 |en modes can be | 00001990 73 65 6c 65 63 74 65 64 20 77 69 74 68 20 74 68 |selected with th| 000019a0 65 20 75 70 20 61 6e 64 0d 64 6f 77 6e 20 63 75 |e up and.down cu| 000019b0 72 73 6f 72 20 6b 65 79 73 20 61 6e 64 20 74 68 |rsor keys and th| 000019c0 65 20 6f 66 66 73 65 74 20 63 61 6e 20 62 65 20 |e offset can be | 000019d0 74 72 69 6d 6d 65 64 20 77 69 74 68 20 74 68 65 |trimmed with the| 000019e0 20 6c 65 66 74 20 61 6e 64 20 72 69 67 68 74 0d | left and right.| 000019f0 63 75 72 73 6f 72 20 6b 65 79 73 2e 20 54 68 65 |cursor keys. 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Yo| 00001ac0 75 20 77 69 6c 6c 0d 70 72 6f 62 61 62 6c 79 20 |u will.probably | 00001ad0 66 69 6e 64 20 74 68 61 74 20 61 20 68 69 67 68 |find that a high| 00001ae0 20 76 61 6c 75 65 20 69 73 20 72 65 71 75 69 72 | value is requir| 00001af0 65 64 20 69 6e 20 6d 6f 64 65 73 20 34 20 61 6e |ed in modes 4 an| 00001b00 64 20 35 20 62 75 74 20 61 20 6c 6f 77 65 72 0d |d 5 but a lower.| 00001b10 76 61 6c 75 65 20 77 69 6c 6c 20 77 6f 72 6b 20 |value will work | 00001b20 71 75 69 74 65 20 77 65 6c 6c 20 69 6e 20 6d 6f |quite well in mo| 00001b30 64 65 73 20 30 2c 20 31 20 61 6e 64 20 32 2e 20 |des 0, 1 and 2. | 00001b40 57 68 65 6e 20 64 69 76 69 73 6f 72 20 3d 20 31 |When divisor = 1| 00001b50 20 74 68 69 73 20 69 73 0d 74 68 65 20 73 61 6d | this is.the sam| 00001b60 65 20 61 73 20 75 73 69 6e 67 20 74 68 65 20 72 |e as using the r| 00001b70 61 77 20 67 72 61 70 68 69 63 73 20 63 6f 6f 72 |aw graphics coor| 00001b80 64 69 6e 61 74 65 73 2e 20 59 6f 75 20 63 61 6e |dinates. You can| 00001b90 20 73 63 72 6f 6c 6c 20 74 68 65 20 73 63 72 65 | scroll the scre| 00001ba0 65 6e 0d 77 69 74 68 20 74 68 65 20 52 65 74 75 |en.with the Retu| 00001bb0 72 6e 20 6b 65 79 20 61 6e 64 20 63 68 61 6e 67 |rn key and chang| 00001bc0 65 20 74 68 65 20 70 61 70 65 72 20 61 6e 64 20 |e the paper and | 00001bd0 69 6e 6b 20 63 6f 6c 6f 75 72 73 20 77 69 74 68 |ink colours with| 00001be0 20 50 20 61 6e 64 20 49 0d 72 65 73 70 65 63 74 | P and I.respect| 00001bf0 69 76 65 6c 79 2e 20 54 68 65 20 70 72 6f 67 72 |ively. 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This effect w| 00001d30 61 73 20 64 65 6d 6f 6e 73 74 72 61 74 65 64 0d |as demonstrated.| 00001d40 69 6e 20 6d 6f 64 75 6c 65 20 31 20 62 75 74 20 |in module 1 but | 00001d50 69 66 20 69 74 20 6f 63 63 75 72 73 20 77 68 65 |if it occurs whe| 00001d60 6e 20 64 72 61 77 69 6e 67 20 73 6d 6f 6f 74 68 |n drawing smooth| 00001d70 65 64 20 6c 69 6e 65 73 20 69 74 20 63 61 6e 20 |ed lines it can | 00001d80 6d 61 6b 65 20 74 68 65 0d 64 72 61 77 69 6e 67 |make the.drawing| 00001d90 20 6c 6f 6f 6b 20 61 20 72 65 61 6c 20 6d 65 73 | look a real mes| 00001da0 73 2e 20 54 68 65 20 70 72 6f 62 6c 65 6d 20 69 |s. The problem i| 00001db0 73 20 6e 6f 74 20 63 75 72 65 64 20 69 6e 20 74 |s not cured in t| 00001dc0 68 65 20 64 65 6d 6f 6e 73 74 72 61 74 69 6f 6e |he demonstration| 00001dd0 0d 70 72 6f 67 72 61 6d 20 62 75 74 20 69 74 20 |.program but it | 00001de0 69 73 20 73 75 70 70 72 65 73 73 65 64 20 62 79 |is suppressed by| 00001df0 20 6e 6f 74 20 70 6c 6f 74 74 69 6e 67 20 61 6e | not plotting an| 00001e00 79 20 70 6f 69 6e 74 73 20 77 68 65 6e 20 74 68 |y points when th| 00001e10 65 20 70 65 6e 20 69 73 20 61 74 0d 65 69 74 68 |e pen is at.eith| 00001e20 65 72 20 74 68 65 20 65 78 74 72 65 6d 65 20 6c |er the extreme l| 00001e30 65 66 74 20 65 64 67 65 20 6f 72 20 74 68 65 20 |eft edge or the | 00001e40 65 78 74 72 65 6d 65 20 72 69 67 68 74 20 65 64 |extreme right ed| 00001e50 67 65 20 6f 66 20 74 68 65 20 73 63 72 65 65 6e |ge of the screen| 00001e60 2e 20 54 68 65 0d 42 41 53 49 43 20 66 75 6e 63 |. The.BASIC func| 00001e70 74 69 6f 6e 20 46 4e 73 77 69 74 63 68 20 28 6c |tion FNswitch (l| 00001e80 69 6e 65 73 20 32 33 33 30 20 74 6f 20 32 33 35 |ines 2330 to 235| 00001e90 30 29 20 69 73 20 75 73 65 64 20 74 6f 20 6d 61 |0) is used to ma| 00001ea0 6b 65 20 74 68 69 73 0d 73 75 70 70 72 65 73 73 |ke this.suppress| 00001eb0 69 6f 6e 2e 20 54 68 65 20 70 65 6e 20 69 73 20 |ion. The pen is | 00001ec0 6f 6e 6c 79 20 73 65 65 6e 20 61 73 20 73 77 69 |only seen as swi| 00001ed0 74 63 68 65 64 20 6f 6e 20 69 66 20 66 69 72 65 |tched on if fire| 00001ee0 20 62 75 74 74 6f 6e 20 32 20 69 73 20 6f 70 65 | button 2 is ope| 00001ef0 6e 0d 28 79 6f 75 20 6d 69 67 68 74 20 6e 65 65 |n.(you might nee| 00001f00 64 20 74 6f 20 6d 6f 64 69 66 79 20 74 68 69 73 |d to modify this| 00001f10 20 63 6f 6e 64 69 74 69 6f 6e 29 20 61 6e 64 20 | condition) and | 00001f20 69 66 20 74 68 65 20 63 75 72 72 65 6e 74 20 70 |if the current p| 00001f30 65 6e 20 70 6f 73 69 74 6f 6e 0d 69 73 20 6e 6f |en positon.is no| 00001f40 74 20 61 74 20 65 69 74 68 65 72 20 74 68 65 20 |t at either the | 00001f50 65 78 74 65 6d 65 20 6c 65 66 74 20 6f 72 20 74 |exteme left or t| 00001f60 68 65 20 65 78 74 72 65 6d 65 20 72 69 67 68 74 |he extreme right| 00001f70 20 6f 66 20 74 68 65 20 73 63 72 65 65 6e 2e 20 | of the screen. | 00001f80 49 0d 77 69 6c 6c 20 6e 6f 74 20 63 6c 61 69 6d |I.will not claim| 00001f90 20 74 68 61 74 20 74 68 65 20 62 65 73 74 20 77 | that the best w| 00001fa0 61 79 20 6f 66 20 63 75 72 69 6e 67 20 61 20 70 |ay of curing a p| 00001fb0 72 6f 62 6c 65 6d 20 69 73 20 74 6f 20 73 75 70 |roblem is to sup| 00001fc0 70 72 65 73 73 20 69 74 20 69 6e 0d 74 68 69 73 |press it in.this| 00001fd0 20 77 61 79 20 62 75 74 20 69 74 20 64 6f 65 73 | way but it does| 00001fe0 20 73 65 65 6d 20 74 6f 20 77 6f 72 6b 20 72 65 | seem to work re| 00001ff0 61 73 6f 6e 61 62 6c 79 20 77 65 6c 6c 20 69 66 |asonably well if| 00002000 20 79 6f 75 20 63 61 6e 20 61 63 63 65 70 74 20 | you can accept | 00002010 61 0d 73 6d 61 6c 6c 20 72 65 64 75 63 74 69 6f |a.small reductio| 00002020 6e 20 69 6e 20 74 68 65 20 61 76 61 69 6c 61 62 |n in the availab| 00002030 6c 65 20 73 63 72 65 65 6e 20 61 72 65 61 2e 20 |le screen area. | 00002040 49 66 20 79 6f 75 20 72 65 6d 6f 76 65 20 74 68 |If you remove th| 00002050 65 20 74 65 73 74 73 20 6f 6e 0d 74 68 65 20 58 |e tests on.the X| 00002060 20 63 6f 6f 72 64 69 6e 61 74 65 20 66 72 6f 6d | coordinate from| 00002070 20 46 4e 73 77 69 74 63 68 20 79 6f 75 20 77 69 | FNswitch you wi| 00002080 6c 6c 20 70 72 6f 62 61 62 6c 79 20 73 65 65 20 |ll probably see | 00002090 74 68 65 20 64 72 65 61 64 66 75 6c 20 6d 65 73 |the dreadful mes| 000020a0 73 0d 74 68 69 73 20 61 70 70 61 72 65 6e 74 6c |s.this apparentl| 000020b0 79 20 74 72 69 76 69 61 6c 20 70 72 6f 62 6c 65 |y trivial proble| 000020c0 6d 20 63 61 6e 20 6d 61 6b 65 20 77 68 65 6e 20 |m can make when | 000020d0 79 6f 75 20 61 72 65 20 64 72 61 77 69 6e 67 20 |you are drawing | 000020e0 61 74 20 74 68 65 20 65 64 67 65 0d 6f 66 20 74 |at the edge.of t| 000020f0 68 65 20 73 63 72 65 65 6e 2e 0d 0d 0d 20 20 20 |he screen.... | 00002100 31 30 20 52 45 4d 3e 20 47 52 41 50 48 49 43 0d |10 REM> GRAPHIC.| 00002110 20 20 20 32 30 20 4f 4e 20 45 52 52 4f 52 20 56 | 20 ON ERROR V| 00002120 44 55 32 33 2c 31 2c 31 3b 30 3b 30 3b 30 3b 3a |DU23,1,1;0;0;0;:| 00002130 45 4e 44 0d 20 20 20 33 30 20 41 25 3d 26 45 41 |END. 30 A%=&EA| 00002140 0d 20 20 20 34 30 20 58 25 3d 30 0d 20 20 20 35 |. 40 X%=0. 5| 00002150 30 20 59 25 3d 26 46 46 0d 20 20 20 36 30 20 49 |0 Y%=&FF. 60 I| 00002160 46 20 28 28 55 53 52 28 26 46 46 46 34 29 41 4e |F ((USR(&FFF4)AN| 00002170 44 26 46 46 30 30 29 44 49 56 26 31 30 30 29 3c |D&FF00)DIV&100)<| 00002180 3e 30 20 45 4e 44 0d 20 20 20 37 30 20 44 49 4d |>0 END. 70 DIM| 00002190 20 6d 63 6f 64 65 20 26 31 30 30 0d 20 20 20 38 | mcode &100. 8| 000021a0 30 20 50 52 4f 43 6d 63 6f 64 65 0d 20 20 20 39 |0 PROCmcode. 9| 000021b0 30 20 6d 6f 64 65 3d 32 0d 20 20 31 30 30 20 64 |0 mode=2. 100 d| 000021c0 69 76 69 73 6f 72 3d 34 0d 20 20 31 31 30 20 70 |ivisor=4. 110 p| 000021d0 61 70 65 72 3d 36 0d 20 20 31 32 30 20 69 6e 6b |aper=6. 120 ink| 000021e0 3d 34 0d 20 20 31 33 30 20 4d 4f 44 45 20 6d 6f |=4. 130 MODE mo| 000021f0 64 65 0d 20 20 31 34 30 20 50 52 4f 43 6e 65 77 |de. 140 PROCnew| 00002200 6d 6f 64 65 0d 20 20 31 35 30 20 52 45 50 45 41 |mode. 150 REPEA| 00002210 54 0d 20 20 31 36 30 20 52 45 50 45 41 54 0d 20 |T. 160 REPEAT. | 00002220 20 31 37 30 20 6f 6c 64 78 3d 6e 65 77 78 0d 20 | 170 oldx=newx. | 00002230 20 31 38 30 20 6f 6c 64 79 3d 6e 65 77 79 0d 20 | 180 oldy=newy. | 00002240 20 31 39 30 20 43 41 4c 4c 20 6d 63 6f 64 65 0d | 190 CALL mcode.| 00002250 20 20 32 30 30 20 50 52 49 4e 54 54 41 42 28 31 | 200 PRINTTAB(1| 00002260 31 2c 31 29 3b 21 78 63 6f 6f 72 64 3b 22 20 20 |1,1);!xcoord;" | 00002270 20 22 54 41 42 28 31 31 2c 32 29 3b 21 79 63 6f | "TAB(11,2);!yco| 00002280 6f 72 64 3b 22 20 20 20 22 0d 20 20 32 31 30 20 |ord;" ". 210 | 00002290 6e 65 77 78 3d 6e 65 77 78 2b 28 28 21 78 63 6f |newx=newx+((!xco| 000022a0 6f 72 64 2d 6e 65 77 78 29 44 49 56 20 64 69 76 |ord-newx)DIV div| 000022b0 69 73 6f 72 29 0d 20 20 32 32 30 20 6e 65 77 79 |isor). 220 newy| 000022c0 3d 6e 65 77 79 2b 28 28 21 79 63 6f 6f 72 64 2d |=newy+((!ycoord-| 000022d0 6e 65 77 79 29 44 49 56 20 64 69 76 69 73 6f 72 |newy)DIV divisor| 000022e0 29 0d 20 20 32 33 30 20 49 46 20 46 4e 73 77 69 |). 230 IF FNswi| 000022f0 74 63 68 20 50 4c 4f 54 36 39 2c 6f 6c 64 78 2c |tch PLOT69,oldx,| 00002300 6f 6c 64 79 3a 50 4c 4f 54 36 39 2c 6e 65 77 78 |oldy:PLOT69,newx| 00002310 2c 6e 65 77 79 0d 20 20 20 20 20 20 45 4c 53 45 |,newy. ELSE| 00002320 20 50 4c 4f 54 31 33 2c 6e 65 77 78 2c 6e 65 77 | PLOT13,newx,new| 00002330 79 0d 20 20 32 34 30 20 55 4e 54 49 4c 20 46 4e |y. 240 UNTIL FN| 00002340 73 77 69 74 63 68 0d 20 20 32 35 30 20 49 46 20 |switch. 250 IF | 00002350 49 4e 4b 45 59 28 2d 35 38 29 20 50 52 4f 43 75 |INKEY(-58) PROCu| 00002360 70 3a 4d 4f 44 45 20 6d 6f 64 65 3a 50 52 4f 43 |p:MODE mode:PROC| 00002370 6e 65 77 6d 6f 64 65 0d 20 20 32 36 30 20 49 46 |newmode. 260 IF| 00002380 20 49 4e 4b 45 59 28 2d 34 32 29 20 50 52 4f 43 | INKEY(-42) PROC| 00002390 64 6f 77 6e 3a 4d 4f 44 45 20 6d 6f 64 65 3a 50 |down:MODE mode:P| 000023a0 52 4f 43 6e 65 77 6d 6f 64 65 0d 20 20 32 37 30 |ROCnewmode. 270| 000023b0 20 49 46 20 49 4e 4b 45 59 28 2d 38 35 29 20 50 | IF INKEY(-85) P| 000023c0 52 4f 43 68 69 67 68 0d 20 20 32 38 30 20 49 46 |ROChigh. 280 IF| 000023d0 20 49 4e 4b 45 59 28 2d 38 37 29 20 50 52 4f 43 | INKEY(-87) PROC| 000023e0 6c 6f 77 0d 20 20 32 39 30 20 49 46 20 49 4e 4b |low. 290 IF INK| 000023f0 45 59 28 2d 35 36 29 20 50 52 4f 43 70 61 70 65 |EY(-56) PROCpape| 00002400 72 0d 20 20 33 30 30 20 49 46 20 49 4e 4b 45 59 |r. 300 IF INKEY| 00002410 28 2d 33 38 29 20 50 52 4f 43 69 6e 6b 0d 20 20 |(-38) PROCink. | 00002420 33 31 30 20 49 46 20 49 4e 4b 45 59 28 2d 32 36 |310 IF INKEY(-26| 00002430 29 20 50 52 4f 43 6c 65 66 74 0d 20 20 33 32 30 |) PROCleft. 320| 00002440 20 49 46 20 49 4e 4b 45 59 28 2d 31 32 32 29 20 | IF INKEY(-122) | 00002450 50 52 4f 43 72 69 67 68 74 0d 20 20 33 33 30 20 |PROCright. 330 | 00002460 49 46 20 49 4e 4b 45 59 28 2d 37 34 29 20 50 52 |IF INKEY(-74) PR| 00002470 4f 43 73 63 72 6f 6c 6c 0d 20 20 33 34 30 20 55 |OCscroll. 340 U| 00002480 4e 54 49 4c 20 46 41 4c 53 45 0d 20 20 33 35 30 |NTIL FALSE. 350| 00002490 20 3a 0d 20 20 33 36 30 20 44 45 46 50 52 4f 43 | :. 360 DEFPROC| 000024a0 73 63 72 6f 6c 6c 0d 20 20 33 37 30 20 50 52 49 |scroll. 370 PRI| 000024b0 4e 54 54 41 42 28 30 2c 33 31 29 0d 20 20 33 38 |NTTAB(0,31). 38| 000024c0 30 20 50 52 4f 43 64 65 6c 61 79 0d 20 20 33 39 |0 PROCdelay. 39| 000024d0 30 20 45 4e 44 50 52 4f 43 0d 20 20 34 30 30 20 |0 ENDPROC. 400 | 000024e0 3a 0d 20 20 34 31 30 20 44 45 46 50 52 4f 43 75 |:. 410 DEFPROCu| 000024f0 70 0d 20 20 34 32 30 20 6d 6f 64 65 3d 6d 6f 64 |p. 420 mode=mod| 00002500 65 2b 31 0d 20 20 34 33 30 20 49 46 20 6d 6f 64 |e+1. 430 IF mod| 00002510 65 3d 33 20 6d 6f 64 65 3d 34 0d 20 20 34 34 30 |e=3 mode=4. 440| 00002520 20 49 46 20 6d 6f 64 65 3e 35 20 6d 6f 64 65 3d | IF mode>5 mode=| 00002530 35 0d 20 20 34 35 30 20 45 4e 44 50 52 4f 43 0d |5. 450 ENDPROC.| 00002540 20 20 34 36 30 20 3a 0d 20 20 34 37 30 20 44 45 | 460 :. 470 DE| 00002550 46 50 52 4f 43 64 6f 77 6e 0d 20 20 34 38 30 20 |FPROCdown. 480 | 00002560 6d 6f 64 65 3d 6d 6f 64 65 2d 31 0d 20 20 34 39 |mode=mode-1. 49| 00002570 30 20 49 46 20 6d 6f 64 65 3d 33 20 6d 6f 64 65 |0 IF mode=3 mode| 00002580 3d 32 0d 20 20 35 30 30 20 49 46 20 6d 6f 64 65 |=2. 500 IF mode| 00002590 3c 30 20 6d 6f 64 65 3d 30 0d 20 20 35 31 30 20 |<0 mode=0. 510 | 000025a0 45 4e 44 50 52 4f 43 0d 20 20 35 32 30 20 3a 0d |ENDPROC. 520 :.| 000025b0 20 20 35 33 30 20 44 45 46 50 52 4f 43 6c 65 66 | 530 DEFPROClef| 000025c0 74 0d 20 20 35 34 30 20 49 46 20 6f 66 66 73 65 |t. 540 IF offse| 000025d0 74 6c 6f 77 3f 6d 6f 64 65 3d 31 32 20 45 4e 44 |tlow?mode=12 END| 000025e0 50 52 4f 43 0d 20 20 35 35 30 20 6f 66 66 73 65 |PROC. 550 offse| 000025f0 74 6c 6f 77 3f 6d 6f 64 65 3d 6f 66 66 73 65 74 |tlow?mode=offset| 00002600 6c 6f 77 3f 6d 6f 64 65 2b 31 0d 20 20 35 36 30 |low?mode+1. 560| 00002610 20 50 52 4f 43 64 65 6c 61 79 0d 20 20 35 37 30 | PROCdelay. 570| 00002620 20 45 4e 44 50 52 4f 43 0d 20 20 35 38 30 20 3a | ENDPROC. 580 :| 00002630 0d 20 20 35 39 30 20 44 45 46 50 52 4f 43 72 69 |. 590 DEFPROCri| 00002640 67 68 74 0d 20 20 36 30 30 20 49 46 20 6f 66 66 |ght. 600 IF off| 00002650 73 65 74 6c 6f 77 3f 6d 6f 64 65 3d 30 20 45 4e |setlow?mode=0 EN| 00002660 44 50 52 4f 43 0d 20 20 36 31 30 20 6f 66 66 73 |DPROC. 610 offs| 00002670 65 74 6c 6f 77 3f 6d 6f 64 65 3d 6f 66 66 73 65 |etlow?mode=offse| 00002680 74 6c 6f 77 3f 6d 6f 64 65 2d 31 0d 20 20 36 32 |tlow?mode-1. 62| 00002690 30 20 50 52 4f 43 64 65 6c 61 79 0d 20 20 36 33 |0 PROCdelay. 63| 000026a0 30 20 45 4e 44 50 52 4f 43 0d 20 20 36 34 30 20 |0 ENDPROC. 640 | 000026b0 3a 0d 20 20 36 35 30 20 44 45 46 50 52 4f 43 6e |:. 650 DEFPROCn| 000026c0 65 77 6d 6f 64 65 0d 20 20 36 36 30 20 56 44 55 |ewmode. 660 VDU| 000026d0 32 33 2c 31 2c 30 3b 30 3b 30 3b 30 3b 0d 20 20 |23,1,0;0;0;0;. | 000026e0 36 37 30 20 56 44 55 31 39 2c 30 2c 70 61 70 65 |670 VDU19,0,pape| 000026f0 72 3b 30 3b 0d 20 20 36 38 30 20 56 44 55 31 39 |r;0;. 680 VDU19| 00002700 2c 31 2c 69 6e 6b 3b 30 3b 0d 20 20 36 39 30 20 |,1,ink;0;. 690 | 00002710 47 43 4f 4c 33 2c 31 0d 20 20 37 30 30 20 43 4f |GCOL3,1. 700 CO| 00002720 4c 4f 55 52 31 0d 20 20 37 31 30 20 6e 65 77 78 |LOUR1. 710 newx| 00002730 3d 2d 31 0d 20 20 37 32 30 20 6e 65 77 79 3d 2d |=-1. 720 newy=-| 00002740 31 0d 20 20 37 33 30 20 6f 6c 64 78 3d 2d 31 0d |1. 730 oldx=-1.| 00002750 20 20 37 34 30 20 6f 6c 64 79 3d 2d 31 0d 20 20 | 740 oldy=-1. | 00002760 37 35 30 20 50 52 4f 43 64 65 6c 61 79 0d 20 20 |750 PROCdelay. | 00002770 37 36 30 20 45 4e 44 50 52 4f 43 0d 20 20 37 37 |760 ENDPROC. 77| 00002780 30 20 3a 0d 20 20 37 38 30 20 44 45 46 50 52 4f |0 :. 780 DEFPRO| 00002790 43 6c 6f 77 0d 20 20 37 39 30 20 49 46 20 64 69 |Clow. 790 IF di| 000027a0 76 69 73 6f 72 3e 31 20 64 69 76 69 73 6f 72 3d |visor>1 divisor=| 000027b0 64 69 76 69 73 6f 72 20 44 49 56 20 32 0d 20 20 |divisor DIV 2. | 000027c0 38 30 30 20 50 52 4f 43 64 65 6c 61 79 0d 20 20 |800 PROCdelay. | 000027d0 38 31 30 20 45 4e 44 50 52 4f 43 0d 20 20 38 32 |810 ENDPROC. 82| 000027e0 30 20 3a 0d 20 20 38 33 30 20 44 45 46 50 52 4f |0 :. 830 DEFPRO| 000027f0 43 68 69 67 68 0d 20 20 38 34 30 20 49 46 20 64 |Chigh. 840 IF d| 00002800 69 76 69 73 6f 72 3c 38 20 64 69 76 69 73 6f 72 |ivisor<8 divisor| 00002810 3d 64 69 76 69 73 6f 72 2a 32 0d 20 20 38 35 30 |=divisor*2. 850| 00002820 20 50 52 4f 43 64 65 6c 61 79 0d 20 20 38 36 30 | PROCdelay. 860| 00002830 20 45 4e 44 50 52 4f 43 0d 20 20 38 37 30 20 3a | ENDPROC. 870 :| 00002840 0d 20 20 38 38 30 20 44 45 46 50 52 4f 43 64 65 |. 880 DEFPROCde| 00002850 6c 61 79 0d 20 20 38 39 30 20 50 52 49 4e 54 54 |lay. 890 PRINTT| 00002860 41 42 28 31 2c 30 29 22 4d 6f 64 65 20 22 3b 6d |AB(1,0)"Mode ";m| 00002870 6f 64 65 3b 53 50 43 28 38 29 0d 20 20 39 30 30 |ode;SPC(8). 900| 00002880 20 50 52 49 4e 54 54 41 42 28 31 2c 31 29 22 58 | PRINTTAB(1,1)"X| 00002890 20 63 6f 6f 72 64 20 3d 20 22 0d 20 20 39 31 30 | coord = ". 910| 000028a0 20 50 52 49 4e 54 54 41 42 28 31 2c 32 29 22 59 | PRINTTAB(1,2)"Y| 000028b0 20 63 6f 6f 72 64 20 3d 20 22 0d 20 20 39 32 30 | coord = ". 920| 000028c0 20 50 52 49 4e 54 54 41 42 28 31 2c 33 29 22 64 | PRINTTAB(1,3)"d| 000028d0 69 76 69 73 6f 72 20 3d 20 22 3b 64 69 76 69 73 |ivisor = ";divis| 000028e0 6f 72 3b 22 20 20 22 0d 20 20 39 33 30 20 50 52 |or;" ". 930 PR| 000028f0 49 4e 54 54 41 42 28 31 2c 34 29 22 6f 66 66 73 |INTTAB(1,4)"offs| 00002900 65 74 6c 6f 77 20 3d 20 22 3b 6f 66 66 73 65 74 |etlow = ";offset| 00002910 6c 6f 77 3f 6d 6f 64 65 0d 20 20 39 34 30 20 74 |low?mode. 940 t| 00002920 69 6d 65 3d 54 49 4d 45 2b 32 30 0d 20 20 39 35 |ime=TIME+20. 95| 00002930 30 20 52 45 50 45 41 54 20 55 4e 54 49 4c 20 74 |0 REPEAT UNTIL t| 00002940 69 6d 65 3c 54 49 4d 45 0d 20 20 39 36 30 20 45 |ime<TIME. 960 E| 00002950 4e 44 50 52 4f 43 0d 20 20 39 37 30 20 3a 0d 20 |NDPROC. 970 :. | 00002960 20 39 38 30 20 44 45 46 50 52 4f 43 69 6e 6b 0d | 980 DEFPROCink.| 00002970 20 20 39 39 30 20 69 6e 6b 3d 69 6e 6b 2b 31 0d | 990 ink=ink+1.| 00002980 20 31 30 30 30 20 49 46 20 69 6e 6b 3d 70 61 70 | 1000 IF ink=pap| 00002990 65 72 20 69 6e 6b 3d 69 6e 6b 2b 31 0d 20 31 30 |er ink=ink+1. 10| 000029a0 31 30 20 49 46 20 69 6e 6b 3e 37 20 69 6e 6b 3d |10 IF ink>7 ink=| 000029b0 30 0d 20 31 30 32 30 20 56 44 55 31 39 2c 31 2c |0. 1020 VDU19,1,| 000029c0 69 6e 6b 3b 30 3b 0d 20 31 30 33 30 20 50 52 4f |ink;0;. 1030 PRO| 000029d0 43 64 65 6c 61 79 0d 20 31 30 34 30 20 45 4e 44 |Cdelay. 1040 END| 000029e0 50 52 4f 43 0d 20 31 30 35 30 20 3a 0d 20 31 30 |PROC. 1050 :. 10| 000029f0 36 30 20 44 45 46 50 52 4f 43 70 61 70 65 72 0d |60 DEFPROCpaper.| 00002a00 20 31 30 37 30 20 70 61 70 65 72 3d 70 61 70 65 | 1070 paper=pape| 00002a10 72 2b 31 0d 20 31 30 38 30 20 49 46 20 70 61 70 |r+1. 1080 IF pap| 00002a20 65 72 3d 69 6e 6b 20 70 61 70 65 72 3d 70 61 70 |er=ink paper=pap| 00002a30 65 72 2b 31 0d 20 31 30 39 30 20 49 46 20 70 61 |er+1. 1090 IF pa| 00002a40 70 65 72 3e 37 20 70 61 70 65 72 3d 30 0d 20 31 |per>7 paper=0. 1| 00002a50 31 30 30 20 56 44 55 31 39 2c 30 2c 70 61 70 65 |100 VDU19,0,pape| 00002a60 72 3b 30 3b 0d 20 31 31 31 30 20 50 52 4f 43 64 |r;0;. 1110 PROCd| 00002a70 65 6c 61 79 0d 20 31 31 32 30 20 45 4e 44 50 52 |elay. 1120 ENDPR| 00002a80 4f 43 0d 20 31 31 33 30 20 3a 0d 20 31 31 34 30 |OC. 1130 :. 1140| 00002a90 20 44 45 46 50 52 4f 43 6d 63 6f 64 65 0d 20 31 | DEFPROCmcode. 1| 00002aa0 31 35 30 20 78 63 6f 6f 72 64 3d 26 37 30 20 3a |150 xcoord=&70 :| 00002ab0 52 45 4d 3a 20 26 37 30 2d 26 37 33 0d 20 31 31 |REM: &70-&73. 11| 00002ac0 36 30 20 79 63 6f 6f 72 64 3d 26 37 34 20 3a 52 |60 ycoord=&74 :R| 00002ad0 45 4d 3a 20 26 37 34 2d 26 37 37 0d 20 31 31 37 |EM: &74-&77. 117| 00002ae0 30 20 73 74 61 72 74 3d 26 33 35 30 20 3a 52 45 |0 start=&350 :RE| 00002af0 4d 3a 20 73 63 72 65 65 6e 20 73 74 61 72 74 20 |M: screen start | 00002b00 61 64 64 72 65 73 73 0d 20 31 31 38 30 20 73 63 |address. 1180 sc| 00002b10 72 65 65 6e 3d 26 33 35 35 20 3a 52 45 4d 3a 20 |reen=&355 :REM: | 00002b20 73 63 72 65 65 6e 20 6d 6f 64 65 0d 20 31 31 39 |screen mode. 119| 00002b30 30 20 73 68 65 69 6c 61 3d 26 46 45 30 30 0d 20 |0 sheila=&FE00. | 00002b40 31 32 30 30 20 46 4f 52 20 70 61 73 73 3d 30 20 |1200 FOR pass=0 | 00002b50 54 4f 20 32 20 53 54 45 50 20 32 0d 20 31 32 31 |TO 2 STEP 2. 121| 00002b60 30 20 50 25 3d 6d 63 6f 64 65 0d 20 31 32 32 30 |0 P%=mcode. 1220| 00002b70 20 5b 20 20 20 20 20 20 20 4f 50 54 20 70 61 73 | [ OPT pas| 00002b80 73 0d 20 31 32 33 30 20 20 20 20 20 20 20 20 20 |s. 1230 | 00002b90 4c 44 41 20 23 26 30 30 0d 20 31 32 34 30 20 20 |LDA #&00. 1240 | 00002ba0 20 20 20 20 20 20 20 4c 44 58 20 23 26 30 37 0d | LDX #&07.| 00002bb0 20 31 32 35 30 20 2e 69 6e 69 74 6c 6f 6f 70 0d | 1250 .initloop.| 00002bc0 20 31 32 36 30 20 20 20 20 20 20 20 20 20 53 54 | 1260 ST| 00002bd0 41 20 78 63 6f 6f 72 64 2c 58 20 20 5c 20 26 37 |A xcoord,X \ &7| 00002be0 30 2d 26 37 37 20 3d 20 23 26 30 30 0d 20 31 32 |0-&77 = #&00. 12| 00002bf0 37 30 20 20 20 20 20 20 20 20 20 44 45 58 0d 20 |70 DEX. | 00002c00 31 32 38 30 20 20 20 20 20 20 20 20 20 42 50 4c |1280 BPL| 00002c10 20 69 6e 69 74 6c 6f 6f 70 0d 20 31 32 39 30 20 | initloop. 1290 | 00002c20 20 20 20 20 20 20 20 20 4c 44 59 20 73 63 72 65 | LDY scre| 00002c30 65 6e 20 20 20 20 5c 20 73 63 72 65 65 6e 20 6d |en \ screen m| 00002c40 6f 64 65 20 69 6e 74 6f 20 59 20 72 65 67 69 73 |ode into Y regis| 00002c50 74 65 72 0d 20 31 33 30 30 20 20 20 20 20 20 20 |ter. 1300 | 00002c60 20 20 43 50 59 20 23 26 30 36 20 20 20 20 20 20 | CPY #&06 | 00002c70 5c 20 69 73 20 74 68 69 73 20 6d 6f 64 65 20 36 |\ is this mode 6| 00002c80 20 6f 72 20 37 3f 0d 20 31 33 31 30 20 20 20 20 | or 7?. 1310 | 00002c90 20 20 20 20 20 42 43 53 20 72 65 74 75 72 6e 20 | BCS return | 00002ca0 20 20 20 5c 20 65 78 69 74 20 69 66 20 6e 6f 6e | \ exit if non| 00002cb0 2d 67 72 61 70 68 69 63 73 20 6d 6f 64 65 0d 20 |-graphics mode. | 00002cc0 31 33 32 30 20 20 20 20 20 20 20 20 20 43 50 59 |1320 CPY| 00002cd0 20 23 26 30 33 20 20 20 20 20 20 5c 20 69 73 20 | #&03 \ is | 00002ce0 74 68 69 73 20 6d 6f 64 65 20 33 3f 0d 20 31 33 |this mode 3?. 13| 00002cf0 33 30 20 20 20 20 20 20 20 20 20 42 4e 45 20 63 |30 BNE c| 00002d00 61 72 72 79 6f 6e 20 20 20 5c 20 65 78 69 74 20 |arryon \ exit | 00002d10 69 66 20 6e 6f 6e 2d 67 72 61 70 68 69 63 73 20 |if non-graphics | 00002d20 6d 6f 64 65 0d 20 31 33 34 30 20 2e 72 65 74 75 |mode. 1340 .retu| 00002d30 72 6e 0d 20 31 33 35 30 20 20 20 20 20 20 20 20 |rn. 1350 | 00002d40 20 52 54 53 20 20 20 20 20 20 20 20 20 20 20 5c | RTS \| 00002d50 20 72 65 74 75 72 6e 20 74 6f 20 42 41 53 49 43 | return to BASIC| 00002d60 20 69 66 20 6e 6f 6e 2d 67 72 61 70 68 69 63 73 | if non-graphics| 00002d70 20 6d 6f 64 65 0d 20 31 33 36 30 20 2e 63 61 72 | mode. 1360 .car| 00002d80 72 79 6f 6e 0d 20 31 33 37 30 20 20 20 20 20 20 |ryon. 1370 | 00002d90 20 20 20 4c 44 41 20 73 74 61 72 74 20 20 20 20 | LDA start | 00002da0 20 5c 20 73 63 72 65 65 6e 20 73 74 61 72 74 20 | \ screen start | 00002db0 61 64 64 72 65 73 73 2c 20 6c 6f 77 20 62 79 74 |address, low byt| 00002dc0 65 0d 20 31 33 38 30 20 20 20 20 20 20 20 20 20 |e. 1380 | 00002dd0 53 54 41 20 79 63 6f 6f 72 64 0d 20 31 33 39 30 |STA ycoord. 1390| 00002de0 20 20 20 20 20 20 20 20 20 4c 44 41 20 73 74 61 | LDA sta| 00002df0 72 74 2b 31 20 20 20 5c 20 73 63 72 65 65 6e 20 |rt+1 \ screen | 00002e00 73 74 61 72 74 20 61 64 64 72 65 73 73 2c 20 68 |start address, h| 00002e10 69 67 68 20 62 79 74 65 0d 20 31 34 30 30 20 20 |igh byte. 1400 | 00002e20 20 20 20 20 20 20 20 53 54 41 20 79 63 6f 6f 72 | STA ycoor| 00002e30 64 2b 31 0d 20 31 34 31 30 20 20 20 20 20 20 20 |d+1. 1410 | 00002e40 20 20 4c 53 52 20 79 63 6f 6f 72 64 2b 31 0d 20 | LSR ycoord+1. | 00002e50 31 34 32 30 20 20 20 20 20 20 20 20 20 52 4f 52 |1420 ROR| 00002e60 20 79 63 6f 6f 72 64 20 20 20 20 5c 20 73 74 61 | ycoord \ sta| 00002e70 72 74 20 61 64 64 72 65 73 73 20 44 49 56 20 32 |rt address DIV 2| 00002e80 0d 20 31 34 33 30 20 20 20 20 20 20 20 20 20 4c |. 1430 L| 00002e90 53 52 20 79 63 6f 6f 72 64 2b 31 0d 20 31 34 34 |SR ycoord+1. 144| 00002ea0 30 20 20 20 20 20 20 20 20 20 52 4f 52 20 79 63 |0 ROR yc| 00002eb0 6f 6f 72 64 20 20 20 20 5c 20 73 74 61 72 74 20 |oord \ start | 00002ec0 61 64 64 72 65 73 73 20 44 49 56 20 34 0d 20 31 |address DIV 4. 1| 00002ed0 34 35 30 20 20 20 20 20 20 20 20 20 4c 53 52 20 |450 LSR | 00002ee0 79 63 6f 6f 72 64 2b 31 0d 20 31 34 36 30 20 20 |ycoord+1. 1460 | 00002ef0 20 20 20 20 20 20 20 52 4f 52 20 79 63 6f 6f 72 | ROR ycoor| 00002f00 64 20 20 20 20 5c 20 73 74 61 72 74 20 61 64 64 |d \ start add| 00002f10 72 65 73 73 20 44 49 56 20 38 0d 20 31 34 37 30 |ress DIV 8. 1470| 00002f20 20 20 20 20 20 20 20 20 20 4c 44 41 20 6f 66 66 | LDA off| 00002f30 73 65 74 6c 6f 77 2c 59 20 5c 20 74 72 69 6d 20 |setlow,Y \ trim | 00002f40 74 68 65 20 6f 66 66 73 65 74 0d 20 31 34 38 30 |the offset. 1480| 00002f50 20 20 20 20 20 20 20 20 20 43 4c 44 20 20 20 20 | CLD | 00002f60 20 20 20 20 20 20 20 5c 20 63 6c 65 61 72 20 64 | \ clear d| 00002f70 65 63 69 6d 61 6c 20 66 6c 61 67 0d 20 31 34 39 |ecimal flag. 149| 00002f80 30 20 20 20 20 20 20 20 20 20 43 4c 43 20 20 20 |0 CLC | 00002f90 20 20 20 20 20 20 20 20 5c 20 70 72 65 70 61 72 | \ prepar| 00002fa0 65 20 66 6f 72 20 61 64 64 69 74 69 6f 6e 0d 20 |e for addition. | 00002fb0 31 35 30 30 20 20 20 20 20 20 20 20 20 41 44 43 |1500 ADC| 00002fc0 20 79 63 6f 6f 72 64 20 20 20 20 5c 20 61 64 64 | ycoord \ add| 00002fd0 20 74 72 69 6d 20 74 6f 20 6f 66 66 73 65 74 0d | trim to offset.| 00002fe0 20 31 35 31 30 20 20 20 20 20 20 20 20 20 53 54 | 1510 ST| 00002ff0 41 20 79 63 6f 6f 72 64 0d 20 31 35 32 30 20 20 |A ycoord. 1520 | 00003000 20 20 20 20 20 20 20 4c 44 41 20 23 26 30 30 0d | LDA #&00.| 00003010 20 31 35 33 30 20 20 20 20 20 20 20 20 20 41 44 | 1530 AD| 00003020 43 20 79 63 6f 6f 72 64 2b 31 0d 20 31 35 34 30 |C ycoord+1. 1540| 00003030 20 20 20 20 20 20 20 20 20 53 54 41 20 79 63 6f | STA yco| 00003040 6f 72 64 2b 31 0d 20 31 35 35 30 20 20 20 20 20 |ord+1. 1550 | 00003050 20 20 20 20 53 45 43 20 20 20 20 20 20 20 20 20 | SEC | 00003060 20 20 5c 20 70 72 65 70 61 72 65 20 74 6f 20 73 | \ prepare to s| 00003070 75 62 74 72 61 63 74 20 6f 66 66 73 65 74 20 66 |ubtract offset f| 00003080 72 6f 6d 20 6c 69 67 68 74 20 70 65 6e 0d 20 20 |rom light pen. | 00003090 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 000030a0 20 20 20 20 20 20 20 20 20 20 5c 20 72 65 67 69 | \ regi| 000030b0 73 74 65 72 0d 20 31 35 36 30 20 20 20 20 20 20 |ster. 1560 | 000030c0 20 20 20 4c 44 58 20 23 26 31 31 20 20 20 20 20 | LDX #&11 | 000030d0 20 5c 20 6c 69 67 68 74 20 70 65 6e 20 72 65 67 | \ light pen reg| 000030e0 69 73 74 65 72 2c 20 6c 6f 77 20 62 79 74 65 0d |ister, low byte.| 000030f0 20 31 35 37 30 20 20 20 20 20 20 20 20 20 53 54 | 1570 ST| 00003100 58 20 73 68 65 69 6c 61 20 20 20 20 5c 20 36 38 |X sheila \ 68| 00003110 34 35 20 61 64 64 72 65 73 73 20 72 65 67 69 73 |45 address regis| 00003120 74 65 72 0d 20 31 35 38 30 20 20 20 20 20 20 20 |ter. 1580 | 00003130 20 20 4c 44 41 20 73 68 65 69 6c 61 2b 31 20 20 | LDA sheila+1 | 00003140 5c 20 36 38 34 35 20 64 61 74 61 20 72 65 67 69 |\ 6845 data regi| 00003150 73 74 65 72 0d 20 31 35 39 30 20 20 20 20 20 20 |ster. 1590 | 00003160 20 20 20 53 42 43 20 79 63 6f 6f 72 64 20 20 20 | SBC ycoord | 00003170 20 5c 20 73 75 62 74 72 61 63 74 20 6f 66 66 73 | \ subtract offs| 00003180 65 74 2c 20 6c 6f 77 20 62 79 74 65 0d 20 31 36 |et, low byte. 16| 00003190 30 30 20 20 20 20 20 20 20 20 20 53 54 41 20 79 |00 STA y| 000031a0 63 6f 6f 72 64 20 20 20 20 5c 20 6c 6f 77 20 62 |coord \ low b| 000031b0 79 74 65 20 2d 20 6f 66 66 73 65 74 0d 20 31 36 |yte - offset. 16| 000031c0 31 30 20 20 20 20 20 20 20 20 20 44 45 58 20 20 |10 DEX | 000031d0 20 20 20 20 20 20 20 20 20 5c 20 58 20 3d 20 23 | \ X = #| 000031e0 26 31 30 0d 20 31 36 32 30 20 20 20 20 20 20 20 |&10. 1620 | 000031f0 20 20 53 54 58 20 73 68 65 69 6c 61 20 20 20 20 | STX sheila | 00003200 5c 20 36 38 34 35 20 61 64 64 72 65 73 73 20 72 |\ 6845 address r| 00003210 65 67 69 73 74 65 72 0d 20 31 36 33 30 20 20 20 |egister. 1630 | 00003220 20 20 20 20 20 20 4c 44 41 20 73 68 65 69 6c 61 | LDA sheila| 00003230 2b 31 20 20 5c 20 36 38 34 35 20 64 61 74 61 20 |+1 \ 6845 data | 00003240 72 65 67 69 73 74 65 72 0d 20 31 36 34 30 20 20 |register. 1640 | 00003250 20 20 20 20 20 20 20 53 42 43 20 79 63 6f 6f 72 | SBC ycoor| 00003260 64 2b 31 20 20 5c 20 73 75 62 74 72 61 63 74 20 |d+1 \ subtract | 00003270 6f 66 66 73 65 74 2c 20 68 69 67 68 20 62 79 74 |offset, high byt| 00003280 65 0d 20 31 36 35 30 20 20 20 20 20 20 20 20 20 |e. 1650 | 00003290 53 54 41 20 79 63 6f 6f 72 64 2b 31 20 20 5c 20 |STA ycoord+1 \ | 000032a0 68 69 67 68 20 62 79 74 65 20 2d 20 6f 66 66 73 |high byte - offs| 000032b0 65 74 0d 20 31 36 36 30 20 2e 6e 65 78 74 0d 20 |et. 1660 .next. | 000032c0 31 36 37 30 20 20 20 20 20 20 20 20 20 41 53 4c |1670 ASL| 000032d0 20 79 63 6f 6f 72 64 20 20 20 20 5c 20 73 68 69 | ycoord \ shi| 000032e0 66 74 20 64 69 76 69 64 65 6e 64 2f 71 75 6f 74 |ft dividend/quot| 000032f0 69 65 6e 74 20 6c 65 66 74 0d 20 31 36 38 30 20 |ient left. 1680 | 00003300 20 20 20 20 20 20 20 20 52 4f 4c 20 79 63 6f 6f | ROL ycoo| 00003310 72 64 2b 31 20 20 5c 20 73 68 69 66 74 20 64 69 |rd+1 \ shift di| 00003320 76 69 64 65 6e 64 2f 71 75 6f 74 69 65 6e 74 20 |vidend/quotient | 00003330 6c 65 66 74 0d 20 31 36 39 30 20 20 20 20 20 20 |left. 1690 | 00003340 20 20 20 52 4f 4c 20 78 63 6f 6f 72 64 20 20 20 | ROL xcoord | 00003350 20 5c 20 73 68 69 66 74 20 62 69 74 73 20 69 6e | \ shift bits in| 00003360 74 6f 20 70 61 72 74 69 61 6c 20 64 69 76 69 64 |to partial divid| 00003370 65 6e 64 0d 20 31 37 30 30 20 20 20 20 20 20 20 |end. 1700 | 00003380 20 20 4c 44 41 20 78 63 6f 6f 72 64 20 20 20 20 | LDA xcoord | 00003390 5c 20 6c 6f 61 64 20 70 61 72 74 69 61 6c 20 64 |\ load partial d| 000033a0 69 76 69 64 65 6e 64 0d 20 31 37 31 30 20 20 20 |ividend. 1710 | 000033b0 20 20 20 20 20 20 53 45 43 20 20 20 20 20 20 20 | SEC | 000033c0 20 20 20 20 5c 20 70 72 65 70 61 72 65 20 66 6f | \ prepare fo| 000033d0 72 20 73 75 62 74 72 61 63 74 69 6f 6e 0d 20 31 |r subtraction. 1| 000033e0 37 32 30 20 20 20 20 20 20 20 20 20 53 42 43 20 |720 SBC | 000033f0 77 69 64 74 68 2c 59 20 20 20 5c 20 73 75 62 74 |width,Y \ subt| 00003400 72 61 63 74 20 64 69 76 69 73 6f 72 0d 20 31 37 |ract divisor. 17| 00003410 33 30 20 20 20 20 20 20 20 20 20 42 43 43 20 64 |30 BCC d| 00003420 6f 6e 65 20 20 20 20 20 20 5c 20 62 72 61 6e 63 |one \ branc| 00003430 68 20 69 66 20 64 69 76 69 64 65 6e 64 20 3c 20 |h if dividend < | 00003440 64 69 76 69 73 6f 72 0d 20 31 37 34 30 20 20 20 |divisor. 1740 | 00003450 20 20 20 20 20 20 49 4e 43 20 79 63 6f 6f 72 64 | INC ycoord| 00003460 20 20 20 20 5c 20 69 6e 63 72 65 6d 65 6e 74 20 | \ increment | 00003470 71 75 6f 74 69 65 6e 74 0d 20 31 37 35 30 20 20 |quotient. 1750 | 00003480 20 20 20 20 20 20 20 53 54 41 20 78 63 6f 6f 72 | STA xcoor| 00003490 64 20 20 20 20 5c 20 73 61 76 65 20 6e 65 77 20 |d \ save new | 000034a0 70 61 72 74 69 61 6c 20 64 69 76 69 64 65 6e 64 |partial dividend| 000034b0 0d 20 31 37 36 30 20 2e 64 6f 6e 65 0d 20 31 37 |. 1760 .done. 17| 000034c0 37 30 20 20 20 20 20 20 20 20 20 44 45 58 20 20 |70 DEX | 000034d0 20 20 20 20 20 20 20 20 20 5c 20 64 65 63 72 65 | \ decre| 000034e0 6d 65 6e 74 20 62 69 74 20 63 6f 75 6e 74 65 72 |ment bit counter| 000034f0 0d 20 31 37 38 30 20 20 20 20 20 20 20 20 20 42 |. 1780 B| 00003500 4e 45 20 6e 65 78 74 20 20 20 20 20 20 5c 20 62 |NE next \ b| 00003510 72 61 6e 63 68 20 66 6f 72 20 31 36 20 62 69 74 |ranch for 16 bit| 00003520 73 0d 20 31 37 39 30 20 20 20 20 20 20 20 20 20 |s. 1790 | 00003530 4c 44 41 20 78 6c 6f 6f 70 2c 59 20 20 20 5c 20 |LDA xloop,Y \ | 00003540 70 72 65 70 61 72 65 20 66 6f 72 20 6d 75 6c 74 |prepare for mult| 00003550 69 70 6c 69 63 61 74 69 6f 6e 0d 20 31 38 30 30 |iplication. 1800| 00003560 20 20 20 20 20 20 20 20 20 54 41 58 20 20 20 20 | TAX | 00003570 20 20 20 20 20 20 20 5c 20 58 3d 34 20 6d 6f 64 | \ X=4 mod| 00003580 65 73 20 30 2d 33 2c 20 58 3d 35 20 6d 6f 64 65 |es 0-3, X=5 mode| 00003590 73 20 34 2d 37 0d 20 31 38 31 30 20 2e 6d 75 6c |s 4-7. 1810 .mul| 000035a0 74 78 0d 20 31 38 32 30 20 20 20 20 20 20 20 20 |tx. 1820 | 000035b0 20 41 53 4c 20 78 63 6f 6f 72 64 20 20 20 20 5c | ASL xcoord \| 000035c0 20 6c 6f 77 20 62 79 74 65 20 2a 20 32 0d 20 31 | low byte * 2. 1| 000035d0 38 33 30 20 20 20 20 20 20 20 20 20 52 4f 4c 20 |830 ROL | 000035e0 78 63 6f 6f 72 64 2b 31 20 20 5c 20 68 69 67 68 |xcoord+1 \ high| 000035f0 20 62 79 74 65 20 2a 20 32 0d 20 31 38 34 30 20 | byte * 2. 1840 | 00003600 20 20 20 20 20 20 20 20 44 45 58 20 20 20 20 20 | DEX | 00003610 20 20 20 20 20 20 5c 20 63 6f 75 6e 74 20 6e 75 | \ count nu| 00003620 6d 62 65 72 20 6f 66 20 6d 75 6c 74 69 70 6c 69 |mber of multipli| 00003630 63 61 74 69 6f 6e 73 0d 20 31 38 35 30 20 20 20 |cations. 1850 | 00003640 20 20 20 20 20 20 42 4e 45 20 6d 75 6c 74 78 20 | BNE multx | 00003650 20 20 20 20 5c 20 67 6f 20 62 61 63 6b 20 69 66 | \ go back if| 00003660 20 6e 6f 74 20 66 69 6e 69 73 68 65 64 0d 20 31 | not finished. 1| 00003670 38 36 30 20 20 20 20 20 20 20 20 20 4c 44 41 20 |860 LDA | 00003680 78 61 64 64 2c 59 20 20 20 20 5c 20 41 3d 38 20 |xadd,Y \ A=8 | 00003690 6d 6f 64 65 73 20 30 2d 33 2c 20 41 3d 31 36 20 |modes 0-3, A=16 | 000036a0 6d 6f 64 65 73 20 34 2d 37 0d 20 31 38 37 30 20 |modes 4-7. 1870 | 000036b0 20 20 20 20 20 20 20 20 43 4c 43 20 20 20 20 20 | CLC | 000036c0 20 20 20 20 20 20 5c 20 70 72 65 70 61 72 65 20 | \ prepare | 000036d0 66 6f 72 20 61 64 64 69 74 69 6f 6e 0d 20 31 38 |for addition. 18| 000036e0 38 30 20 20 20 20 20 20 20 20 20 41 44 43 20 78 |80 ADC x| 000036f0 63 6f 6f 72 64 0d 20 31 38 39 30 20 20 20 20 20 |coord. 1890 | 00003700 20 20 20 20 53 54 41 20 78 63 6f 6f 72 64 0d 20 | STA xcoord. | 00003710 31 39 30 30 20 20 20 20 20 20 20 20 20 4c 44 41 |1900 LDA| 00003720 20 23 26 30 30 0d 20 31 39 31 30 20 20 20 20 20 | #&00. 1910 | 00003730 20 20 20 20 41 44 43 20 78 63 6f 6f 72 64 2b 31 | ADC xcoord+1| 00003740 0d 20 31 39 32 30 20 20 20 20 20 20 20 20 20 43 |. 1920 C| 00003750 4d 50 20 23 26 30 35 20 20 20 20 20 20 5c 20 6d |MP #&05 \ m| 00003760 61 78 20 76 61 6c 75 65 20 3d 20 34 0d 20 31 39 |ax value = 4. 19| 00003770 33 30 20 20 20 20 20 20 20 20 20 42 43 43 20 69 |30 BCC i| 00003780 6e 72 61 6e 67 65 0d 20 31 39 34 30 20 20 20 20 |nrange. 1940 | 00003790 20 20 20 20 20 4c 44 41 20 23 26 30 32 20 20 20 | LDA #&02 | 000037a0 20 20 20 5c 20 64 75 6d 6d 79 20 76 61 6c 75 65 | \ dummy value| 000037b0 0d 20 31 39 35 30 20 2e 69 6e 72 61 6e 67 65 0d |. 1950 .inrange.| 000037c0 20 31 39 36 30 20 20 20 20 20 20 20 20 20 53 54 | 1960 ST| 000037d0 41 20 78 63 6f 6f 72 64 2b 31 0d 20 31 39 37 30 |A xcoord+1. 1970| 000037e0 20 20 20 20 20 20 20 20 20 4c 44 58 20 23 26 30 | LDX #&0| 000037f0 35 20 20 20 20 20 20 5c 20 70 72 65 70 61 72 65 |5 \ prepare| 00003800 20 66 6f 72 20 79 20 63 6f 6f 72 64 69 6e 61 74 | for y coordinat| 00003810 65 20 6d 75 6c 74 69 70 6c 69 63 61 74 69 6f 6e |e multiplication| 00003820 0d 20 31 39 38 30 20 2e 6d 75 6c 74 79 0d 20 31 |. 1980 .multy. 1| 00003830 39 39 30 20 20 20 20 20 20 20 20 20 41 53 4c 20 |990 ASL | 00003840 79 63 6f 6f 72 64 20 20 20 20 5c 20 6c 6f 77 20 |ycoord \ low | 00003850 62 79 74 65 20 2a 20 32 0d 20 32 30 30 30 20 20 |byte * 2. 2000 | 00003860 20 20 20 20 20 20 20 52 4f 4c 20 79 63 6f 6f 72 | ROL ycoor| 00003870 64 2b 31 20 20 5c 20 68 69 67 68 20 62 79 74 65 |d+1 \ high byte| 00003880 20 2a 20 32 0d 20 32 30 31 30 20 20 20 20 20 20 | * 2. 2010 | 00003890 20 20 20 44 45 58 20 20 20 20 20 20 20 20 20 20 | DEX | 000038a0 20 5c 20 63 6f 75 6e 74 20 6e 75 6d 62 65 72 20 | \ count number | 000038b0 6f 66 20 6d 75 6c 74 69 70 6c 69 63 61 74 69 6f |of multiplicatio| 000038c0 6e 73 0d 20 32 30 32 30 20 20 20 20 20 20 20 20 |ns. 2020 | 000038d0 20 42 4e 45 20 6d 75 6c 74 79 20 20 20 20 20 5c | BNE multy \| 000038e0 20 67 6f 20 62 61 63 6b 20 69 66 20 6e 6f 74 20 | go back if not | 000038f0 66 69 6e 69 73 68 65 64 0d 20 32 30 33 30 20 20 |finished. 2030 | 00003900 20 20 20 20 20 20 20 53 45 43 20 20 20 20 20 20 | SEC | 00003910 20 20 20 20 20 5c 20 70 72 65 70 61 72 65 20 66 | \ prepare f| 00003920 6f 72 20 73 75 62 74 72 61 63 74 69 6f 6e 0d 20 |or subtraction. | 00003930 32 30 34 30 20 20 20 20 20 20 20 20 20 4c 44 41 |2040 LDA| 00003940 20 23 26 46 30 20 20 20 20 20 20 5c 20 6c 6f 77 | #&F0 \ low| 00003950 20 62 79 74 65 20 6f 66 20 64 65 63 69 6d 61 6c | byte of decimal| 00003960 20 31 30 30 38 0d 20 32 30 35 30 20 20 20 20 20 | 1008. 2050 | 00003970 20 20 20 20 53 42 43 20 79 63 6f 6f 72 64 20 20 | SBC ycoord | 00003980 20 20 5c 20 79 63 6f 6f 72 64 2d 23 26 46 30 0d | \ ycoord-#&F0.| 00003990 20 32 30 36 30 20 20 20 20 20 20 20 20 20 53 54 | 2060 ST| 000039a0 41 20 79 63 6f 6f 72 64 0d 20 32 30 37 30 20 20 |A ycoord. 2070 | 000039b0 20 20 20 20 20 20 20 4c 44 41 20 23 26 30 33 20 | LDA #&03 | 000039c0 20 20 20 20 20 5c 20 68 69 67 68 20 62 79 74 65 | \ high byte| 000039d0 20 6f 66 20 64 65 63 69 6d 61 6c 20 31 30 30 38 | of decimal 1008| 000039e0 0d 20 32 30 38 30 20 20 20 20 20 20 20 20 20 53 |. 2080 S| 000039f0 42 43 20 79 63 6f 6f 72 64 2b 31 20 20 5c 20 28 |BC ycoord+1 \ (| 00003a00 79 63 6f 6f 72 64 2b 31 29 2d 23 26 30 33 0d 20 |ycoord+1)-#&03. | 00003a10 32 30 39 30 20 20 20 20 20 20 20 20 20 41 4e 44 |2090 AND| 00003a20 20 23 26 30 33 20 20 20 20 20 20 5c 20 6d 61 78 | #&03 \ max| 00003a30 20 76 61 6c 75 65 20 3d 20 33 0d 20 32 31 30 30 | value = 3. 2100| 00003a40 20 20 20 20 20 20 20 20 20 53 54 41 20 79 63 6f | STA yco| 00003a50 6f 72 64 2b 31 0d 20 32 31 31 30 20 20 20 20 20 |ord+1. 2110 | 00003a60 20 20 20 20 52 54 53 20 20 20 20 20 20 20 20 20 | RTS | 00003a70 20 20 5c 20 72 65 74 75 72 6e 20 74 6f 20 42 41 | \ return to BA| 00003a80 53 49 43 0d 20 32 31 32 30 20 2e 6f 66 66 73 65 |SIC. 2120 .offse| 00003a90 74 6c 6f 77 0d 20 32 31 33 30 20 20 20 20 20 20 |tlow. 2130 | 00003aa0 20 20 20 45 51 55 42 20 26 30 34 20 20 20 20 20 | EQUB &04 | 00003ab0 20 5c 20 6d 6f 64 65 30 2c 20 75 6e 74 72 69 6d | \ mode0, untrim| 00003ac0 6d 65 64 20 3d 20 26 30 36 0d 20 32 31 34 30 20 |med = &06. 2140 | 00003ad0 20 20 20 20 20 20 20 20 45 51 55 42 20 26 30 34 | EQUB &04| 00003ae0 20 20 20 20 20 20 5c 20 6d 6f 64 65 31 2c 20 75 | \ mode1, u| 00003af0 6e 74 72 69 6d 6d 65 64 20 3d 20 26 30 36 0d 20 |ntrimmed = &06. | 00003b00 32 31 35 30 20 20 20 20 20 20 20 20 20 45 51 55 |2150 EQU| 00003b10 42 20 26 30 34 20 20 20 20 20 20 5c 20 6d 6f 64 |B &04 \ mod| 00003b20 65 32 2c 20 75 6e 74 72 69 6d 6d 65 64 20 3d 20 |e2, untrimmed = | 00003b30 26 30 36 0d 20 32 31 36 30 20 20 20 20 20 20 20 |&06. 2160 | 00003b40 20 20 45 51 55 42 20 26 30 30 20 20 20 20 20 20 | EQUB &00 | 00003b50 5c 20 6d 6f 64 65 33 2c 20 64 75 6d 6d 79 20 76 |\ mode3, dummy v| 00003b60 61 6c 75 65 0d 20 32 31 37 30 20 20 20 20 20 20 |alue. 2170 | 00003b70 20 20 20 45 51 55 42 20 26 30 33 20 20 20 20 20 | EQUB &03 | 00003b80 20 5c 20 6d 6f 64 65 34 2c 20 75 6e 74 72 69 6d | \ mode4, untrim| 00003b90 6d 65 64 20 3d 20 26 30 34 0d 20 32 31 38 30 20 |med = &04. 2180 | 00003ba0 20 20 20 20 20 20 20 20 45 51 55 42 20 26 30 33 | EQUB &03| 00003bb0 20 20 20 20 20 20 5c 20 6d 6f 64 65 35 2c 20 75 | \ mode5, u| 00003bc0 6e 74 72 69 6d 6d 65 64 20 3d 20 26 30 34 0d 20 |ntrimmed = &04. | 00003bd0 32 31 39 30 20 2e 78 6c 6f 6f 70 0d 20 32 32 30 |2190 .xloop. 220| 00003be0 30 20 20 20 20 20 20 20 20 20 45 51 55 44 20 26 |0 EQUD &| 00003bf0 30 30 30 34 30 34 30 34 20 5c 20 6d 6f 64 65 73 |00040404 \ modes| 00003c00 20 33 2d 30 0d 20 32 32 31 30 20 20 20 20 20 20 | 3-0. 2210 | 00003c10 20 20 20 45 51 55 57 20 26 30 35 30 35 20 20 20 | EQUW &0505 | 00003c20 20 5c 20 6d 6f 64 65 73 20 35 2d 34 0d 20 32 32 | \ modes 5-4. 22| 00003c30 32 30 20 2e 78 61 64 64 0d 20 32 32 33 30 20 20 |20 .xadd. 2230 | 00003c40 20 20 20 20 20 20 20 45 51 55 44 20 26 30 30 30 | EQUD &000| 00003c50 38 30 38 30 38 20 5c 20 6d 6f 64 65 73 20 33 2d |80808 \ modes 3-| 00003c60 30 0d 20 32 32 34 30 20 20 20 20 20 20 20 20 20 |0. 2240 | 00003c70 45 51 55 57 20 26 31 30 31 30 20 20 20 20 5c 20 |EQUW &1010 \ | 00003c80 6d 6f 64 65 73 20 35 2d 34 0d 20 32 32 35 30 20 |modes 5-4. 2250 | 00003c90 2e 77 69 64 74 68 0d 20 32 32 36 30 20 20 20 20 |.width. 2260 | 00003ca0 20 20 20 20 20 45 51 55 44 20 26 30 30 35 30 35 | EQUD &00505| 00003cb0 30 35 30 20 5c 20 6d 6f 64 65 73 20 33 2d 30 0d |050 \ modes 3-0.| 00003cc0 20 32 32 37 30 20 20 20 20 20 20 20 20 20 45 51 | 2270 EQ| 00003cd0 55 57 20 26 32 38 32 38 20 20 20 20 5c 20 6d 6f |UW &2828 \ mo| 00003ce0 64 65 73 20 35 2d 34 0d 20 32 32 38 30 20 2e 6c |des 5-4. 2280 .l| 00003cf0 61 73 74 62 79 74 65 0d 20 32 32 39 30 20 5d 0d |astbyte. 2290 ].| 00003d00 20 32 33 30 30 20 4e 45 58 54 0d 20 32 33 31 30 | 2300 NEXT. 2310| 00003d10 20 45 4e 44 50 52 4f 43 0d 20 32 33 32 30 20 3a | ENDPROC. 2320 :| 00003d20 20 0d 20 32 33 33 30 20 44 45 46 46 4e 73 77 69 | . 2330 DEFFNswi| 00003d30 74 63 68 0d 20 32 33 34 30 20 49 46 20 28 41 44 |tch. 2340 IF (AD| 00003d40 56 41 4c 28 30 29 41 4e 44 33 29 3d 30 20 49 46 |VAL(0)AND3)=0 IF| 00003d50 20 21 78 63 6f 6f 72 64 3e 31 36 20 49 46 20 21 | !xcoord>16 IF !| 00003d60 78 63 6f 6f 72 64 3c 31 32 34 38 20 3d 46 41 4c |xcoord<1248 =FAL| 00003d70 53 45 0d 20 32 33 35 30 20 3d 54 52 55 45 0d |SE. 2350 =TRUE.| 00003d7f
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