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shipwren/PT/+P3
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 » Personal collection » Acorn hard disk » misc » misc3 |
Filename: | shipwren/PT/+P3 |
Read OK: | ✔ |
File size: | 0BD3 bytes |
Load address: | 0000 |
Exec address: | 0000 |
Duplicates
There are 5 duplicate copies of this file in the archive:
- Personal collection » Acorn ADFS disks » Archimedes » Unlabelled_disk_2.ADF » PT/+P3
- Personal collection » Acorn ADFS disks » Electron_User_Group » EUG_35.ADF » P/+P3
- Personal collection » Acorn ADFS disks » Electron_User_Group » EUG_36.ADF » F/+P3
- Personal collection » Acorn hard disk » misc » misc3 » shipwren/PT/+P3
- Personal collection » Acorn hard disk » zipped_disks » elk03 » eug35/P/+P3
- Personal collection » Acorn hard disk » zipped_disks » elk03 » eug36/F/+P3
File contents
This is where MOVE, DRAW and PLOT are useful. Using these commands, lines can be drawn across the screen, and, using PLOT, triangles can be drawn. These commands are covered in the Graphics chapter of the user manual. The other major advantage of these graphics commands is that they can be used not just to set the colour of an area, but also to invert it. The GCOL command, which selects the colour in which graphics are displayed, takes two parameters: GCOL x,c c is the new colour in which graphics should be drawn. x selects how this colour should be applyed: x=0 means to set every pixel to that colour, regardless of its previous colour. x=1 means to mix the light from the pixel already on the screen with that of the new colour. For example, if a red pixel is set to blue, the red and blue mix to form purple. x=2 means that the light from the pixels is filtered with the new colour. If a red pixel is set to blue now, it is as if a blue filter has been placed in front of the red light, and the resultant colour is black (red light contains no blue component). x=3 means to invert the old colour with the new colour. x=4 means to set the pixels with the inverse of the new colour (regardless of the old colour). Lines may now be drawn across the screen by typing: MOVE x,y:DRAW xb,yb Where: (x,y) = The co-ordinate of the first point on the line. (xb,yb) = That of the last point on the line. The range of the screen is always 1280 pixels across, and 1024 pixels down. The bottom left corner is point (0,0), and the top right corner is (1280,1024). Larger graphics can be drawn using the PLOT command. The most common usage is as follows: MOVE x,y: MOVE xb,yb:PLOT 85,xc,yc This plots a filled triangle with corners at (x,y), (xb,yb) and (xc,yc). PLOT also has many other functions - see the User Guide for details. At first sight, it may seem that user defined characters serve no purpose once a programmer has learnt about the more flexible graphics commands, but this is not the case. If you try to produce detailed graphics using MOVE and DRAW, you will find that your program crawls along at an unacceptable rate. User defined characters, on the other hand, can produce detail quickly, especially if the pattern repeats, so that one character definition can be used repeatedly in several areas of the screen. This is demonstrated by the program which is available at the end of the tutorial. So, it seems that programmers are faced with a difficult problem. They can use graphics commands and get colour, or they can use user defined characters and get detail, but what if they want both at the same time? There must be a solution - how else would games like Citadel manage to produce such detailed colourful graphics, and at such a speed? There are, in fact, two possible solutions, both of which involve dealing with an area of memory known as screen memory. This is, however, very complicated, and will be discussed further in the next article.
00000000 20 20 20 20 20 54 68 69 73 20 69 73 20 77 68 65 | This is whe| 00000010 72 65 20 4d 4f 56 45 2c 20 44 52 41 57 20 61 6e |re MOVE, DRAW an| 00000020 64 20 50 4c 4f 54 20 61 72 65 20 75 73 65 66 75 |d PLOT are usefu| 00000030 6c 2e 20 55 73 69 6e 67 20 74 68 65 73 65 20 63 |l. Using these c| 00000040 6f 6d 6d 61 6e 64 73 2c 0d 6c 69 6e 65 73 20 63 |ommands,.lines c| 00000050 61 6e 20 62 65 20 64 72 61 77 6e 20 61 63 72 6f |an be drawn acro| 00000060 73 73 20 74 68 65 20 73 63 72 65 65 6e 2c 20 61 |ss the screen, a| 00000070 6e 64 2c 20 75 73 69 6e 67 20 50 4c 4f 54 2c 20 |nd, using PLOT, | 00000080 74 72 69 61 6e 67 6c 65 73 20 63 61 6e 20 62 65 |triangles can be| 00000090 0d 64 72 61 77 6e 2e 20 54 68 65 73 65 20 63 6f |.drawn. These co| 000000a0 6d 6d 61 6e 64 73 20 61 72 65 20 63 6f 76 65 72 |mmands are cover| 000000b0 65 64 20 69 6e 20 74 68 65 20 47 72 61 70 68 69 |ed in the Graphi| 000000c0 63 73 20 63 68 61 70 74 65 72 20 6f 66 20 74 68 |cs chapter of th| 000000d0 65 20 75 73 65 72 0d 6d 61 6e 75 61 6c 2e 20 54 |e user.manual. T| 000000e0 68 65 20 6f 74 68 65 72 20 6d 61 6a 6f 72 20 61 |he other major a| 000000f0 64 76 61 6e 74 61 67 65 20 6f 66 20 74 68 65 73 |dvantage of thes| 00000100 65 20 67 72 61 70 68 69 63 73 20 63 6f 6d 6d 61 |e graphics comma| 00000110 6e 64 73 20 69 73 20 74 68 61 74 20 74 68 65 79 |nds is that they| 00000120 0d 63 61 6e 20 62 65 20 75 73 65 64 20 6e 6f 74 |.can be used not| 00000130 20 6a 75 73 74 20 74 6f 20 73 65 74 20 74 68 65 | just to set the| 00000140 20 63 6f 6c 6f 75 72 20 6f 66 20 61 6e 20 61 72 | colour of an ar| 00000150 65 61 2c 20 62 75 74 20 61 6c 73 6f 20 74 6f 20 |ea, but also to | 00000160 69 6e 76 65 72 74 20 69 74 2e 0d 54 68 65 20 47 |invert it..The G| 00000170 43 4f 4c 20 63 6f 6d 6d 61 6e 64 2c 20 77 68 69 |COL command, whi| 00000180 63 68 20 73 65 6c 65 63 74 73 20 74 68 65 20 63 |ch selects the c| 00000190 6f 6c 6f 75 72 20 69 6e 20 77 68 69 63 68 20 67 |olour in which g| 000001a0 72 61 70 68 69 63 73 20 61 72 65 0d 64 69 73 70 |raphics are.disp| 000001b0 6c 61 79 65 64 2c 20 74 61 6b 65 73 20 74 77 6f |layed, takes two| 000001c0 20 70 61 72 61 6d 65 74 65 72 73 3a 0d 0d 47 43 | parameters:..GC| 000001d0 4f 4c 20 78 2c 63 0d 0d 63 20 69 73 20 74 68 65 |OL x,c..c is the| 000001e0 20 6e 65 77 20 63 6f 6c 6f 75 72 20 69 6e 20 77 | new colour in w| 000001f0 68 69 63 68 20 67 72 61 70 68 69 63 73 20 73 68 |hich graphics sh| 00000200 6f 75 6c 64 20 62 65 20 64 72 61 77 6e 2e 0d 78 |ould be drawn..x| 00000210 20 73 65 6c 65 63 74 73 20 68 6f 77 20 74 68 69 | selects how thi| 00000220 73 20 63 6f 6c 6f 75 72 20 73 68 6f 75 6c 64 20 |s colour should | 00000230 62 65 20 61 70 70 6c 79 65 64 3a 0d 0d 78 3d 30 |be applyed:..x=0| 00000240 20 6d 65 61 6e 73 20 74 6f 20 73 65 74 20 65 76 | means to set ev| 00000250 65 72 79 20 70 69 78 65 6c 20 74 6f 20 74 68 61 |ery pixel to tha| 00000260 74 20 63 6f 6c 6f 75 72 2c 20 72 65 67 61 72 64 |t colour, regard| 00000270 6c 65 73 73 20 6f 66 20 69 74 73 20 0d 70 72 65 |less of its .pre| 00000280 76 69 6f 75 73 20 63 6f 6c 6f 75 72 2e 0d 78 3d |vious colour..x=| 00000290 31 20 6d 65 61 6e 73 20 74 6f 20 6d 69 78 20 74 |1 means to mix t| 000002a0 68 65 20 6c 69 67 68 74 20 66 72 6f 6d 20 74 68 |he light from th| 000002b0 65 20 70 69 78 65 6c 20 61 6c 72 65 61 64 79 20 |e pixel already | 000002c0 6f 6e 20 74 68 65 20 73 63 72 65 65 6e 20 0d 77 |on the screen .w| 000002d0 69 74 68 20 74 68 61 74 20 6f 66 20 74 68 65 20 |ith that of the | 000002e0 6e 65 77 20 63 6f 6c 6f 75 72 2e 20 46 6f 72 20 |new colour. For | 000002f0 65 78 61 6d 70 6c 65 2c 20 69 66 20 61 20 72 65 |example, if a re| 00000300 64 20 70 69 78 65 6c 20 69 73 20 73 65 74 20 0d |d pixel is set .| 00000310 74 6f 20 62 6c 75 65 2c 20 74 68 65 20 72 65 64 |to blue, the red| 00000320 20 61 6e 64 20 62 6c 75 65 20 6d 69 78 20 74 6f | and blue mix to| 00000330 20 66 6f 72 6d 20 70 75 72 70 6c 65 2e 0d 78 3d | form purple..x=| 00000340 32 20 6d 65 61 6e 73 20 74 68 61 74 20 74 68 65 |2 means that the| 00000350 20 6c 69 67 68 74 20 66 72 6f 6d 20 74 68 65 20 | light from the | 00000360 70 69 78 65 6c 73 20 69 73 20 66 69 6c 74 65 72 |pixels is filter| 00000370 65 64 20 77 69 74 68 20 74 68 65 20 6e 65 77 20 |ed with the new | 00000380 0d 63 6f 6c 6f 75 72 2e 20 49 66 20 61 20 72 65 |.colour. If a re| 00000390 64 20 70 69 78 65 6c 20 69 73 20 73 65 74 20 74 |d pixel is set t| 000003a0 6f 20 62 6c 75 65 20 6e 6f 77 2c 20 69 74 20 69 |o blue now, it i| 000003b0 73 20 61 73 20 69 66 20 61 20 62 6c 75 65 20 0d |s as if a blue .| 000003c0 66 69 6c 74 65 72 20 68 61 73 20 62 65 65 6e 20 |filter has been | 000003d0 70 6c 61 63 65 64 20 69 6e 20 66 72 6f 6e 74 20 |placed in front | 000003e0 6f 66 20 74 68 65 20 72 65 64 20 6c 69 67 68 74 |of the red light| 000003f0 2c 20 61 6e 64 20 74 68 65 20 0d 72 65 73 75 6c |, and the .resul| 00000400 74 61 6e 74 20 63 6f 6c 6f 75 72 20 69 73 20 62 |tant colour is b| 00000410 6c 61 63 6b 20 28 72 65 64 20 6c 69 67 68 74 20 |lack (red light | 00000420 63 6f 6e 74 61 69 6e 73 20 6e 6f 20 62 6c 75 65 |contains no blue| 00000430 20 63 6f 6d 70 6f 6e 65 6e 74 29 2e 0d 78 3d 33 | component)..x=3| 00000440 20 6d 65 61 6e 73 20 74 6f 20 69 6e 76 65 72 74 | means to invert| 00000450 20 74 68 65 20 6f 6c 64 20 63 6f 6c 6f 75 72 20 | the old colour | 00000460 77 69 74 68 20 74 68 65 20 6e 65 77 20 63 6f 6c |with the new col| 00000470 6f 75 72 2e 0d 78 3d 34 20 6d 65 61 6e 73 20 74 |our..x=4 means t| 00000480 6f 20 73 65 74 20 74 68 65 20 70 69 78 65 6c 73 |o set the pixels| 00000490 20 77 69 74 68 20 74 68 65 20 69 6e 76 65 72 73 | with the invers| 000004a0 65 20 6f 66 20 74 68 65 20 6e 65 77 20 63 6f 6c |e of the new col| 000004b0 6f 75 72 20 0d 28 72 65 67 61 72 64 6c 65 73 73 |our .(regardless| 000004c0 20 6f 66 20 74 68 65 20 6f 6c 64 20 63 6f 6c 6f | of the old colo| 000004d0 75 72 29 2e 0d 0d 20 20 20 20 20 4c 69 6e 65 73 |ur)... Lines| 000004e0 20 6d 61 79 20 6e 6f 77 20 62 65 20 64 72 61 77 | may now be draw| 000004f0 6e 20 61 63 72 6f 73 73 20 74 68 65 20 73 63 72 |n across the scr| 00000500 65 65 6e 20 62 79 20 74 79 70 69 6e 67 3a 0d 0d |een by typing:..| 00000510 4d 4f 56 45 20 78 2c 79 3a 44 52 41 57 20 78 62 |MOVE x,y:DRAW xb| 00000520 2c 79 62 0d 0d 57 68 65 72 65 3a 20 28 78 2c 79 |,yb..Where: (x,y| 00000530 29 20 20 20 3d 20 54 68 65 20 63 6f 2d 6f 72 64 |) = The co-ord| 00000540 69 6e 61 74 65 20 6f 66 20 74 68 65 20 66 69 72 |inate of the fir| 00000550 73 74 20 70 6f 69 6e 74 20 6f 6e 20 74 68 65 20 |st point on the | 00000560 6c 69 6e 65 2e 0d 20 20 20 20 20 20 20 28 78 62 |line.. (xb| 00000570 2c 79 62 29 20 3d 20 54 68 61 74 20 6f 66 20 74 |,yb) = That of t| 00000580 68 65 20 6c 61 73 74 20 70 6f 69 6e 74 20 6f 6e |he last point on| 00000590 20 74 68 65 20 6c 69 6e 65 2e 0d 0d 20 20 20 20 | the line... | 000005a0 20 54 68 65 20 72 61 6e 67 65 20 6f 66 20 74 68 | The range of th| 000005b0 65 20 73 63 72 65 65 6e 20 69 73 20 61 6c 77 61 |e screen is alwa| 000005c0 79 73 20 31 32 38 30 20 70 69 78 65 6c 73 20 61 |ys 1280 pixels a| 000005d0 63 72 6f 73 73 2c 20 61 6e 64 20 31 30 32 34 20 |cross, and 1024 | 000005e0 70 69 78 65 6c 73 20 0d 64 6f 77 6e 2e 20 54 68 |pixels .down. Th| 000005f0 65 20 62 6f 74 74 6f 6d 20 6c 65 66 74 20 63 6f |e bottom left co| 00000600 72 6e 65 72 20 69 73 20 70 6f 69 6e 74 20 28 30 |rner is point (0| 00000610 2c 30 29 2c 20 61 6e 64 20 74 68 65 20 74 6f 70 |,0), and the top| 00000620 20 72 69 67 68 74 20 63 6f 72 6e 65 72 20 69 73 | right corner is| 00000630 20 0d 28 31 32 38 30 2c 31 30 32 34 29 2e 20 4c | .(1280,1024). L| 00000640 61 72 67 65 72 20 67 72 61 70 68 69 63 73 20 63 |arger graphics c| 00000650 61 6e 20 62 65 20 64 72 61 77 6e 20 75 73 69 6e |an be drawn usin| 00000660 67 20 74 68 65 20 50 4c 4f 54 20 63 6f 6d 6d 61 |g the PLOT comma| 00000670 6e 64 2e 20 54 68 65 20 6d 6f 73 74 20 0d 63 6f |nd. The most .co| 00000680 6d 6d 6f 6e 20 75 73 61 67 65 20 69 73 20 61 73 |mmon usage is as| 00000690 20 66 6f 6c 6c 6f 77 73 3a 0d 0d 4d 4f 56 45 20 | follows:..MOVE | 000006a0 78 2c 79 3a 20 4d 4f 56 45 20 78 62 2c 79 62 3a |x,y: MOVE xb,yb:| 000006b0 50 4c 4f 54 20 38 35 2c 78 63 2c 79 63 0d 0d 20 |PLOT 85,xc,yc.. | 000006c0 20 20 20 20 54 68 69 73 20 70 6c 6f 74 73 20 61 | This plots a| 000006d0 20 66 69 6c 6c 65 64 20 74 72 69 61 6e 67 6c 65 | filled triangle| 000006e0 20 77 69 74 68 20 63 6f 72 6e 65 72 73 20 61 74 | with corners at| 000006f0 20 28 78 2c 79 29 2c 20 28 78 62 2c 79 62 29 20 | (x,y), (xb,yb) | 00000700 61 6e 64 20 0d 28 78 63 2c 79 63 29 2e 20 50 4c |and .(xc,yc). PL| 00000710 4f 54 20 61 6c 73 6f 20 68 61 73 20 6d 61 6e 79 |OT also has many| 00000720 20 6f 74 68 65 72 20 66 75 6e 63 74 69 6f 6e 73 | other functions| 00000730 20 2d 20 73 65 65 20 74 68 65 20 55 73 65 72 20 | - see the User | 00000740 47 75 69 64 65 20 66 6f 72 20 64 65 74 61 69 6c |Guide for detail| 00000750 73 2e 0d 20 20 20 20 20 41 74 20 66 69 72 73 74 |s.. At first| 00000760 20 73 69 67 68 74 2c 20 69 74 20 6d 61 79 20 73 | sight, it may s| 00000770 65 65 6d 20 74 68 61 74 20 75 73 65 72 20 64 65 |eem that user de| 00000780 66 69 6e 65 64 20 63 68 61 72 61 63 74 65 72 73 |fined characters| 00000790 20 73 65 72 76 65 20 6e 6f 0d 70 75 72 70 6f 73 | serve no.purpos| 000007a0 65 20 6f 6e 63 65 20 61 20 70 72 6f 67 72 61 6d |e once a program| 000007b0 6d 65 72 20 68 61 73 20 6c 65 61 72 6e 74 20 61 |mer has learnt a| 000007c0 62 6f 75 74 20 74 68 65 20 6d 6f 72 65 20 66 6c |bout the more fl| 000007d0 65 78 69 62 6c 65 20 67 72 61 70 68 69 63 73 0d |exible graphics.| 000007e0 63 6f 6d 6d 61 6e 64 73 2c 20 62 75 74 20 74 68 |commands, but th| 000007f0 69 73 20 69 73 20 6e 6f 74 20 74 68 65 20 63 61 |is is not the ca| 00000800 73 65 2e 20 49 66 20 79 6f 75 20 74 72 79 20 74 |se. If you try t| 00000810 6f 20 70 72 6f 64 75 63 65 20 64 65 74 61 69 6c |o produce detail| 00000820 65 64 0d 67 72 61 70 68 69 63 73 20 75 73 69 6e |ed.graphics usin| 00000830 67 20 4d 4f 56 45 20 61 6e 64 20 44 52 41 57 2c |g MOVE and DRAW,| 00000840 20 79 6f 75 20 77 69 6c 6c 20 66 69 6e 64 20 74 | you will find t| 00000850 68 61 74 20 79 6f 75 72 20 70 72 6f 67 72 61 6d |hat your program| 00000860 20 63 72 61 77 6c 73 0d 61 6c 6f 6e 67 20 61 74 | crawls.along at| 00000870 20 61 6e 20 75 6e 61 63 63 65 70 74 61 62 6c 65 | an unacceptable| 00000880 20 72 61 74 65 2e 20 55 73 65 72 20 64 65 66 69 | rate. User defi| 00000890 6e 65 64 20 63 68 61 72 61 63 74 65 72 73 2c 20 |ned characters, | 000008a0 6f 6e 20 74 68 65 20 6f 74 68 65 72 0d 68 61 6e |on the other.han| 000008b0 64 2c 20 63 61 6e 20 70 72 6f 64 75 63 65 20 64 |d, can produce d| 000008c0 65 74 61 69 6c 20 71 75 69 63 6b 6c 79 2c 20 65 |etail quickly, e| 000008d0 73 70 65 63 69 61 6c 6c 79 20 69 66 20 74 68 65 |specially if the| 000008e0 20 70 61 74 74 65 72 6e 20 72 65 70 65 61 74 73 | pattern repeats| 000008f0 2c 20 73 6f 0d 74 68 61 74 20 6f 6e 65 20 63 68 |, so.that one ch| 00000900 61 72 61 63 74 65 72 20 64 65 66 69 6e 69 74 69 |aracter definiti| 00000910 6f 6e 20 63 61 6e 20 62 65 20 75 73 65 64 20 72 |on can be used r| 00000920 65 70 65 61 74 65 64 6c 79 20 69 6e 20 73 65 76 |epeatedly in sev| 00000930 65 72 61 6c 20 61 72 65 61 73 20 6f 66 0d 74 68 |eral areas of.th| 00000940 65 20 73 63 72 65 65 6e 2e 20 54 68 69 73 20 69 |e screen. This i| 00000950 73 20 64 65 6d 6f 6e 73 74 72 61 74 65 64 20 62 |s demonstrated b| 00000960 79 20 74 68 65 20 70 72 6f 67 72 61 6d 20 77 68 |y the program wh| 00000970 69 63 68 20 69 73 20 61 76 61 69 6c 61 62 6c 65 |ich is available| 00000980 20 61 74 20 74 68 65 0d 65 6e 64 20 6f 66 20 74 | at the.end of t| 00000990 68 65 20 74 75 74 6f 72 69 61 6c 2e 0d 20 20 20 |he tutorial.. | 000009a0 20 20 53 6f 2c 20 69 74 20 73 65 65 6d 73 20 74 | So, it seems t| 000009b0 68 61 74 20 70 72 6f 67 72 61 6d 6d 65 72 73 20 |hat programmers | 000009c0 61 72 65 20 66 61 63 65 64 20 77 69 74 68 20 61 |are faced with a| 000009d0 20 64 69 66 66 69 63 75 6c 74 20 70 72 6f 62 6c | difficult probl| 000009e0 65 6d 2e 0d 54 68 65 79 20 63 61 6e 20 75 73 65 |em..They can use| 000009f0 20 67 72 61 70 68 69 63 73 20 63 6f 6d 6d 61 6e | graphics comman| 00000a00 64 73 20 61 6e 64 20 67 65 74 20 63 6f 6c 6f 75 |ds and get colou| 00000a10 72 2c 20 6f 72 20 74 68 65 79 20 63 61 6e 20 75 |r, or they can u| 00000a20 73 65 20 75 73 65 72 0d 64 65 66 69 6e 65 64 20 |se user.defined | 00000a30 63 68 61 72 61 63 74 65 72 73 20 61 6e 64 20 67 |characters and g| 00000a40 65 74 20 64 65 74 61 69 6c 2c 20 62 75 74 20 77 |et detail, but w| 00000a50 68 61 74 20 69 66 20 74 68 65 79 20 77 61 6e 74 |hat if they want| 00000a60 20 62 6f 74 68 20 61 74 20 74 68 65 20 73 61 6d | both at the sam| 00000a70 65 0d 74 69 6d 65 3f 20 54 68 65 72 65 20 6d 75 |e.time? There mu| 00000a80 73 74 20 62 65 20 61 20 73 6f 6c 75 74 69 6f 6e |st be a solution| 00000a90 20 2d 20 68 6f 77 20 65 6c 73 65 20 77 6f 75 6c | - how else woul| 00000aa0 64 20 67 61 6d 65 73 20 6c 69 6b 65 20 43 69 74 |d games like Cit| 00000ab0 61 64 65 6c 20 6d 61 6e 61 67 65 0d 74 6f 20 70 |adel manage.to p| 00000ac0 72 6f 64 75 63 65 20 73 75 63 68 20 64 65 74 61 |roduce such deta| 00000ad0 69 6c 65 64 20 63 6f 6c 6f 75 72 66 75 6c 20 67 |iled colourful g| 00000ae0 72 61 70 68 69 63 73 2c 20 61 6e 64 20 61 74 20 |raphics, and at | 00000af0 73 75 63 68 20 61 20 73 70 65 65 64 3f 0d 20 20 |such a speed?. | 00000b00 20 20 20 54 68 65 72 65 20 61 72 65 2c 20 69 6e | There are, in| 00000b10 20 66 61 63 74 2c 20 74 77 6f 20 70 6f 73 73 69 | fact, two possi| 00000b20 62 6c 65 20 73 6f 6c 75 74 69 6f 6e 73 2c 20 62 |ble solutions, b| 00000b30 6f 74 68 20 6f 66 20 77 68 69 63 68 20 69 6e 76 |oth of which inv| 00000b40 6f 6c 76 65 0d 64 65 61 6c 69 6e 67 20 77 69 74 |olve.dealing wit| 00000b50 68 20 61 6e 20 61 72 65 61 20 6f 66 20 6d 65 6d |h an area of mem| 00000b60 6f 72 79 20 6b 6e 6f 77 6e 20 61 73 20 73 63 72 |ory known as scr| 00000b70 65 65 6e 20 6d 65 6d 6f 72 79 2e 20 54 68 69 73 |een memory. This| 00000b80 20 69 73 2c 20 68 6f 77 65 76 65 72 2c 0d 76 65 | is, however,.ve| 00000b90 72 79 20 63 6f 6d 70 6c 69 63 61 74 65 64 2c 20 |ry complicated, | 00000ba0 61 6e 64 20 77 69 6c 6c 20 62 65 20 64 69 73 63 |and will be disc| 00000bb0 75 73 73 65 64 20 66 75 72 74 68 65 72 20 69 6e |ussed further in| 00000bc0 20 74 68 65 20 6e 65 78 74 20 61 72 74 69 63 6c | the next articl| 00000bd0 65 2e 0d |e..| 00000bd3