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shipwren/PT/+P1
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/+P1 |
| Read OK: | ✔ |
| File size: | 0FB7 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/+P1
- Personal collection » Acorn ADFS disks » Electron_User_Group » EUG_35.ADF » P/+P1
- Personal collection » Acorn ADFS disks » Electron_User_Group » EUG_36.ADF » F/+P1
- Personal collection » Acorn hard disk » misc » misc3 » shipwren/PT/+P1
- Personal collection » Acorn hard disk » zipped_disks » elk03 » eug35/P/+P1
- Personal collection » Acorn hard disk » zipped_disks » elk03 » eug36/F/+P1
File contents
PROGRAMMING TECHNIQUE
by Dominic Ford
Part 2: Graphics
The most important decision which you must make when you are writing
the graphics routines for a program is which graphics mode to use. There
are seven different display types available on the Electron, and an
eighth is available on the BBC. Each display type has its own
characteristics, and you must choose which is most suitable for your
particular program. Some graphics modes, for example, allow you to have
many different colours on screen, but poor detail, while others allow you
to have very great detail but few colours. You select graphics modes by
using the MODE x command. Details of the seven different available modes
are given below:
x Colours Graphics? Res/G Res/T Memory
0 2 Yes 640x256 80x32 20K
1 4 Yes 320x256 40x32 20K
2 16 Yes 160x256 20x32 20K
3 2 No N/A 80x25 16K
4 2 Yes 320x256 40x32 10K
5 4 Yes 160x256 20x32 10K
6 2 No N/A 40x25 8K
7 16 No N/A 40x25 1K <- BBC ONLY!
KEY:
x: MODE number.
Colours: The maximum number of different colours which may be used on
screen at any one time.
Graphics?: Does this graphics mode allow the use of the graphics commands
(ie. MOVE, DRAW, etc.)? Modes 3 & 6 do not allow these commands, as there
are thin horizontal stripes in between the rows of characters, in which
nothing can be displayed. Thus, any graphics drawn in these modes would
have black horizontal stripes across them, and would look rather silly!
To see what I mean, turn on your computer and type:
MODE 6:COLOUR 129:COLOUR 0:CLS
The background should be entirely white, but there are horizontal stripes
where the screen can be no colour except black.
Res/G: The resolution of the screen in this mode (ie. the number of
pixels across and down the screen). Generally, the higher the value, the
smoother your graphics will look. Note that this is not the same as the
parameters taken by the MOVE and DRAW commands - these always scale the
number of pixels across the screen to 1280 and down the screen to 1024,
so that (1280,1024) will always be the top-right corner of the screen,
and (0,0) the bottom left.
Res/T: The number of characters which fit across the screen in this mode
when using text.
Memory: The amount of the computer's 32K of memory which is used by the
graphics mode. If you are writing a long program, this is an important
consideration, as you may not have room for the program after subtracting
20K from the computer's 32K RAM for a MODE 2 screen. If this is the case,
you must use a mode which uses less memory, such as mode 5.
My advice in choosing which mode to use would be to try, if at all
possible, to use one of the 20K modes. The detail of MODE 1, and the
colours of MODE 2, are both far superior to the quality of MODE 5. If you
are an efficient programmer, you should find that it is perfectly
possible to fit a reasonably lengthed program into memory at the same
time as 20K of screen. Shipwrecked, for example, used MODE 2 for its
graphics, as does Shipwrecked II on this issue.
Fitting a program into memory as well as a large screen memory is
fairly easy when you are using a tape or DFS filing system, but this can
prove difficult with ADFS, because 4K of the memory normally used to
store programs is taken away for the ADFS to use, leaving you only a mere
4.5K free for programs. Assuming that once you have loaded the program
you do not intend to use the disk again, there is a way around this. If
you switch over to a tape filing system, the ADFS memory becomes
redundant and can be reclaimed for BASIC use. Once you have done this, of
course, you cannot access disks without resetting the computer, so load
and save options in your program are restricted to tape only. This
technique will be explained in greater depth in a later article on memory
management.
00000000 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000010 20 20 20 20 20 20 20 20 20 50 52 4f 47 52 41 4d | PROGRAM| 00000020 4d 49 4e 47 20 54 45 43 48 4e 49 51 55 45 0d 20 |MING TECHNIQUE. | 00000030 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000040 20 20 20 20 20 20 20 20 20 20 62 79 20 44 6f 6d | by Dom| 00000050 69 6e 69 63 20 46 6f 72 64 0d 20 20 20 20 20 20 |inic Ford. | 00000060 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000070 20 20 20 20 20 50 61 72 74 20 32 3a 20 47 72 61 | Part 2: Gra| 00000080 70 68 69 63 73 0d 0d 20 20 20 20 20 54 68 65 20 |phics.. The | 00000090 6d 6f 73 74 20 69 6d 70 6f 72 74 61 6e 74 20 64 |most important d| 000000a0 65 63 69 73 69 6f 6e 20 77 68 69 63 68 20 79 6f |ecision which yo| 000000b0 75 20 6d 75 73 74 20 6d 61 6b 65 20 77 68 65 6e |u must make when| 000000c0 20 79 6f 75 20 61 72 65 20 77 72 69 74 69 6e 67 | you are writing| 000000d0 0d 74 68 65 20 67 72 61 70 68 69 63 73 20 72 6f |.the graphics ro| 000000e0 75 74 69 6e 65 73 20 66 6f 72 20 61 20 70 72 6f |utines for a pro| 000000f0 67 72 61 6d 20 69 73 20 77 68 69 63 68 20 67 72 |gram is which gr| 00000100 61 70 68 69 63 73 20 6d 6f 64 65 20 74 6f 20 75 |aphics mode to u| 00000110 73 65 2e 20 54 68 65 72 65 0d 61 72 65 20 73 65 |se. There.are se| 00000120 76 65 6e 20 64 69 66 66 65 72 65 6e 74 20 64 69 |ven different di| 00000130 73 70 6c 61 79 20 74 79 70 65 73 20 61 76 61 69 |splay types avai| 00000140 6c 61 62 6c 65 20 6f 6e 20 74 68 65 20 45 6c 65 |lable on the Ele| 00000150 63 74 72 6f 6e 2c 20 61 6e 64 20 61 6e 0d 65 69 |ctron, and an.ei| 00000160 67 68 74 68 20 69 73 20 61 76 61 69 6c 61 62 6c |ghth is availabl| 00000170 65 20 6f 6e 20 74 68 65 20 42 42 43 2e 20 45 61 |e on the BBC. Ea| 00000180 63 68 20 64 69 73 70 6c 61 79 20 74 79 70 65 20 |ch display type | 00000190 68 61 73 20 69 74 73 20 6f 77 6e 0d 63 68 61 72 |has its own.char| 000001a0 61 63 74 65 72 69 73 74 69 63 73 2c 20 61 6e 64 |acteristics, and| 000001b0 20 79 6f 75 20 6d 75 73 74 20 63 68 6f 6f 73 65 | you must choose| 000001c0 20 77 68 69 63 68 20 69 73 20 6d 6f 73 74 20 73 | which is most s| 000001d0 75 69 74 61 62 6c 65 20 66 6f 72 20 79 6f 75 72 |uitable for your| 000001e0 0d 70 61 72 74 69 63 75 6c 61 72 20 70 72 6f 67 |.particular prog| 000001f0 72 61 6d 2e 20 53 6f 6d 65 20 67 72 61 70 68 69 |ram. Some graphi| 00000200 63 73 20 6d 6f 64 65 73 2c 20 66 6f 72 20 65 78 |cs modes, for ex| 00000210 61 6d 70 6c 65 2c 20 61 6c 6c 6f 77 20 79 6f 75 |ample, allow you| 00000220 20 74 6f 20 68 61 76 65 0d 6d 61 6e 79 20 64 69 | to have.many di| 00000230 66 66 65 72 65 6e 74 20 63 6f 6c 6f 75 72 73 20 |fferent colours | 00000240 6f 6e 20 73 63 72 65 65 6e 2c 20 62 75 74 20 70 |on screen, but p| 00000250 6f 6f 72 20 64 65 74 61 69 6c 2c 20 77 68 69 6c |oor detail, whil| 00000260 65 20 6f 74 68 65 72 73 20 61 6c 6c 6f 77 20 79 |e others allow y| 00000270 6f 75 0d 74 6f 20 68 61 76 65 20 76 65 72 79 20 |ou.to have very | 00000280 67 72 65 61 74 20 64 65 74 61 69 6c 20 62 75 74 |great detail but| 00000290 20 66 65 77 20 63 6f 6c 6f 75 72 73 2e 20 59 6f | few colours. Yo| 000002a0 75 20 73 65 6c 65 63 74 20 67 72 61 70 68 69 63 |u select graphic| 000002b0 73 20 6d 6f 64 65 73 20 62 79 0d 75 73 69 6e 67 |s modes by.using| 000002c0 20 74 68 65 20 4d 4f 44 45 20 78 20 63 6f 6d 6d | the MODE x comm| 000002d0 61 6e 64 2e 20 44 65 74 61 69 6c 73 20 6f 66 20 |and. Details of | 000002e0 74 68 65 20 73 65 76 65 6e 20 64 69 66 66 65 72 |the seven differ| 000002f0 65 6e 74 20 61 76 61 69 6c 61 62 6c 65 20 6d 6f |ent available mo| 00000300 64 65 73 0d 61 72 65 20 67 69 76 65 6e 20 62 65 |des.are given be| 00000310 6c 6f 77 3a 0d 0d 78 20 43 6f 6c 6f 75 72 73 20 |low:..x Colours | 00000320 47 72 61 70 68 69 63 73 3f 20 52 65 73 2f 47 20 |Graphics? Res/G | 00000330 20 20 52 65 73 2f 54 20 20 4d 65 6d 6f 72 79 0d | Res/T Memory.| 00000340 30 20 20 20 32 20 20 20 20 20 20 59 65 73 20 20 |0 2 Yes | 00000350 20 20 20 20 36 34 30 78 32 35 36 20 38 30 78 33 | 640x256 80x3| 00000360 32 20 20 20 32 30 4b 0d 31 20 20 20 34 20 20 20 |2 20K.1 4 | 00000370 20 20 20 59 65 73 20 20 20 20 20 20 33 32 30 78 | Yes 320x| 00000380 32 35 36 20 34 30 78 33 32 20 20 20 32 30 4b 0d |256 40x32 20K.| 00000390 32 20 20 20 31 36 20 20 20 20 20 59 65 73 20 20 |2 16 Yes | 000003a0 20 20 20 20 31 36 30 78 32 35 36 20 32 30 78 33 | 160x256 20x3| 000003b0 32 20 20 20 32 30 4b 0d 33 20 20 20 32 20 20 20 |2 20K.3 2 | 000003c0 20 20 20 4e 6f 20 20 20 20 20 20 20 4e 2f 41 20 | No N/A | 000003d0 20 20 20 20 38 30 78 32 35 20 20 20 31 36 4b 0d | 80x25 16K.| 000003e0 34 20 20 20 32 20 20 20 20 20 20 59 65 73 20 20 |4 2 Yes | 000003f0 20 20 20 20 33 32 30 78 32 35 36 20 34 30 78 33 | 320x256 40x3| 00000400 32 20 20 20 31 30 4b 0d 35 20 20 20 34 20 20 20 |2 10K.5 4 | 00000410 20 20 20 59 65 73 20 20 20 20 20 20 31 36 30 78 | Yes 160x| 00000420 32 35 36 20 32 30 78 33 32 20 20 20 31 30 4b 0d |256 20x32 10K.| 00000430 36 20 20 20 32 20 20 20 20 20 20 4e 6f 20 20 20 |6 2 No | 00000440 20 20 20 20 4e 2f 41 20 20 20 20 20 34 30 78 32 | N/A 40x2| 00000450 35 20 20 20 38 4b 0d 37 20 20 20 31 36 20 20 20 |5 8K.7 16 | 00000460 20 20 4e 6f 20 20 20 20 20 20 20 4e 2f 41 20 20 | No N/A | 00000470 20 20 20 34 30 78 32 35 20 20 20 31 4b 20 3c 2d | 40x25 1K <-| 00000480 20 42 42 43 20 4f 4e 4c 59 21 0d 0d 4b 45 59 3a | BBC ONLY!..KEY:| 00000490 0d 0d 78 3a 20 4d 4f 44 45 20 6e 75 6d 62 65 72 |..x: MODE number| 000004a0 2e 0d 0d 43 6f 6c 6f 75 72 73 3a 20 54 68 65 20 |...Colours: The | 000004b0 6d 61 78 69 6d 75 6d 20 6e 75 6d 62 65 72 20 6f |maximum number o| 000004c0 66 20 64 69 66 66 65 72 65 6e 74 20 63 6f 6c 6f |f different colo| 000004d0 75 72 73 20 77 68 69 63 68 20 6d 61 79 20 62 65 |urs which may be| 000004e0 20 75 73 65 64 20 6f 6e 0d 73 63 72 65 65 6e 20 | used on.screen | 000004f0 61 74 20 61 6e 79 20 6f 6e 65 20 74 69 6d 65 2e |at any one time.| 00000500 0d 0d 47 72 61 70 68 69 63 73 3f 3a 20 44 6f 65 |..Graphics?: Doe| 00000510 73 20 74 68 69 73 20 67 72 61 70 68 69 63 73 20 |s this graphics | 00000520 6d 6f 64 65 20 61 6c 6c 6f 77 20 74 68 65 20 75 |mode allow the u| 00000530 73 65 20 6f 66 20 74 68 65 20 67 72 61 70 68 69 |se of the graphi| 00000540 63 73 20 63 6f 6d 6d 61 6e 64 73 0d 28 69 65 2e |cs commands.(ie.| 00000550 20 4d 4f 56 45 2c 20 44 52 41 57 2c 20 65 74 63 | MOVE, DRAW, etc| 00000560 2e 29 3f 20 4d 6f 64 65 73 20 33 20 26 20 36 20 |.)? Modes 3 & 6 | 00000570 64 6f 20 6e 6f 74 20 61 6c 6c 6f 77 20 74 68 65 |do not allow the| 00000580 73 65 20 63 6f 6d 6d 61 6e 64 73 2c 20 61 73 20 |se commands, as | 00000590 74 68 65 72 65 0d 61 72 65 20 74 68 69 6e 20 68 |there.are thin h| 000005a0 6f 72 69 7a 6f 6e 74 61 6c 20 73 74 72 69 70 65 |orizontal stripe| 000005b0 73 20 69 6e 20 62 65 74 77 65 65 6e 20 74 68 65 |s in between the| 000005c0 20 72 6f 77 73 20 6f 66 20 63 68 61 72 61 63 74 | rows of charact| 000005d0 65 72 73 2c 20 69 6e 20 77 68 69 63 68 0d 6e 6f |ers, in which.no| 000005e0 74 68 69 6e 67 20 63 61 6e 20 62 65 20 64 69 73 |thing can be dis| 000005f0 70 6c 61 79 65 64 2e 20 54 68 75 73 2c 20 61 6e |played. Thus, an| 00000600 79 20 67 72 61 70 68 69 63 73 20 64 72 61 77 6e |y graphics drawn| 00000610 20 69 6e 20 74 68 65 73 65 20 6d 6f 64 65 73 20 | in these modes | 00000620 77 6f 75 6c 64 0d 68 61 76 65 20 62 6c 61 63 6b |would.have black| 00000630 20 68 6f 72 69 7a 6f 6e 74 61 6c 20 73 74 72 69 | horizontal stri| 00000640 70 65 73 20 61 63 72 6f 73 73 20 74 68 65 6d 2c |pes across them,| 00000650 20 61 6e 64 20 77 6f 75 6c 64 20 6c 6f 6f 6b 20 | and would look | 00000660 72 61 74 68 65 72 20 73 69 6c 6c 79 21 0d 54 6f |rather silly!.To| 00000670 20 73 65 65 20 77 68 61 74 20 49 20 6d 65 61 6e | see what I mean| 00000680 2c 20 74 75 72 6e 20 6f 6e 20 79 6f 75 72 20 63 |, turn on your c| 00000690 6f 6d 70 75 74 65 72 20 61 6e 64 20 74 79 70 65 |omputer and type| 000006a0 3a 0d 4d 4f 44 45 20 36 3a 43 4f 4c 4f 55 52 20 |:.MODE 6:COLOUR | 000006b0 31 32 39 3a 43 4f 4c 4f 55 52 20 30 3a 43 4c 53 |129:COLOUR 0:CLS| 000006c0 0d 54 68 65 20 62 61 63 6b 67 72 6f 75 6e 64 20 |.The background | 000006d0 73 68 6f 75 6c 64 20 62 65 20 65 6e 74 69 72 65 |should be entire| 000006e0 6c 79 20 77 68 69 74 65 2c 20 62 75 74 20 74 68 |ly white, but th| 000006f0 65 72 65 20 61 72 65 20 68 6f 72 69 7a 6f 6e 74 |ere are horizont| 00000700 61 6c 20 73 74 72 69 70 65 73 0d 77 68 65 72 65 |al stripes.where| 00000710 20 74 68 65 20 73 63 72 65 65 6e 20 63 61 6e 20 | the screen can | 00000720 62 65 20 6e 6f 20 63 6f 6c 6f 75 72 20 65 78 63 |be no colour exc| 00000730 65 70 74 20 62 6c 61 63 6b 2e 0d 0d 52 65 73 2f |ept black...Res/| 00000740 47 3a 20 54 68 65 20 72 65 73 6f 6c 75 74 69 6f |G: The resolutio| 00000750 6e 20 6f 66 20 74 68 65 20 73 63 72 65 65 6e 20 |n of the screen | 00000760 69 6e 20 74 68 69 73 20 6d 6f 64 65 20 28 69 65 |in this mode (ie| 00000770 2e 20 74 68 65 20 6e 75 6d 62 65 72 20 6f 66 20 |. the number of | 00000780 0d 70 69 78 65 6c 73 20 61 63 72 6f 73 73 20 61 |.pixels across a| 00000790 6e 64 20 64 6f 77 6e 20 74 68 65 20 73 63 72 65 |nd down the scre| 000007a0 65 6e 29 2e 20 47 65 6e 65 72 61 6c 6c 79 2c 20 |en). Generally, | 000007b0 74 68 65 20 68 69 67 68 65 72 20 74 68 65 20 76 |the higher the v| 000007c0 61 6c 75 65 2c 20 74 68 65 0d 73 6d 6f 6f 74 68 |alue, the.smooth| 000007d0 65 72 20 79 6f 75 72 20 67 72 61 70 68 69 63 73 |er your graphics| 000007e0 20 77 69 6c 6c 20 6c 6f 6f 6b 2e 20 4e 6f 74 65 | will look. Note| 000007f0 20 74 68 61 74 20 74 68 69 73 20 69 73 20 6e 6f | that this is no| 00000800 74 20 74 68 65 20 73 61 6d 65 20 61 73 20 74 68 |t the same as th| 00000810 65 0d 70 61 72 61 6d 65 74 65 72 73 20 74 61 6b |e.parameters tak| 00000820 65 6e 20 62 79 20 74 68 65 20 4d 4f 56 45 20 61 |en by the MOVE a| 00000830 6e 64 20 44 52 41 57 20 63 6f 6d 6d 61 6e 64 73 |nd DRAW commands| 00000840 20 2d 20 74 68 65 73 65 20 61 6c 77 61 79 73 20 | - these always | 00000850 73 63 61 6c 65 20 74 68 65 0d 6e 75 6d 62 65 72 |scale the.number| 00000860 20 6f 66 20 70 69 78 65 6c 73 20 61 63 72 6f 73 | of pixels acros| 00000870 73 20 74 68 65 20 73 63 72 65 65 6e 20 74 6f 20 |s the screen to | 00000880 31 32 38 30 20 61 6e 64 20 64 6f 77 6e 20 74 68 |1280 and down th| 00000890 65 20 73 63 72 65 65 6e 20 74 6f 20 31 30 32 34 |e screen to 1024| 000008a0 2c 0d 73 6f 20 74 68 61 74 20 28 31 32 38 30 2c |,.so that (1280,| 000008b0 31 30 32 34 29 20 77 69 6c 6c 20 61 6c 77 61 79 |1024) will alway| 000008c0 73 20 62 65 20 74 68 65 20 74 6f 70 2d 72 69 67 |s be the top-rig| 000008d0 68 74 20 63 6f 72 6e 65 72 20 6f 66 20 74 68 65 |ht corner of the| 000008e0 20 73 63 72 65 65 6e 2c 0d 61 6e 64 20 28 30 2c | screen,.and (0,| 000008f0 30 29 20 74 68 65 20 62 6f 74 74 6f 6d 20 6c 65 |0) the bottom le| 00000900 66 74 2e 0d 0d 52 65 73 2f 54 3a 20 54 68 65 20 |ft...Res/T: The | 00000910 6e 75 6d 62 65 72 20 6f 66 20 63 68 61 72 61 63 |number of charac| 00000920 74 65 72 73 20 77 68 69 63 68 20 66 69 74 20 61 |ters which fit a| 00000930 63 72 6f 73 73 20 74 68 65 20 73 63 72 65 65 6e |cross the screen| 00000940 20 69 6e 20 74 68 69 73 20 6d 6f 64 65 0d 77 68 | in this mode.wh| 00000950 65 6e 20 75 73 69 6e 67 20 74 65 78 74 2e 0d 0d |en using text...| 00000960 4d 65 6d 6f 72 79 3a 20 54 68 65 20 61 6d 6f 75 |Memory: The amou| 00000970 6e 74 20 6f 66 20 74 68 65 20 63 6f 6d 70 75 74 |nt of the comput| 00000980 65 72 27 73 20 33 32 4b 20 6f 66 20 6d 65 6d 6f |er's 32K of memo| 00000990 72 79 20 77 68 69 63 68 20 69 73 20 75 73 65 64 |ry which is used| 000009a0 20 62 79 20 74 68 65 0d 67 72 61 70 68 69 63 73 | by the.graphics| 000009b0 20 6d 6f 64 65 2e 20 49 66 20 79 6f 75 20 61 72 | mode. If you ar| 000009c0 65 20 77 72 69 74 69 6e 67 20 61 20 6c 6f 6e 67 |e writing a long| 000009d0 20 70 72 6f 67 72 61 6d 2c 20 74 68 69 73 20 69 | program, this i| 000009e0 73 20 61 6e 20 69 6d 70 6f 72 74 61 6e 74 20 0d |s an important .| 000009f0 63 6f 6e 73 69 64 65 72 61 74 69 6f 6e 2c 20 61 |consideration, a| 00000a00 73 20 79 6f 75 20 6d 61 79 20 6e 6f 74 20 68 61 |s you may not ha| 00000a10 76 65 20 72 6f 6f 6d 20 66 6f 72 20 74 68 65 20 |ve room for the | 00000a20 70 72 6f 67 72 61 6d 20 61 66 74 65 72 20 73 75 |program after su| 00000a30 62 74 72 61 63 74 69 6e 67 0d 32 30 4b 20 66 72 |btracting.20K fr| 00000a40 6f 6d 20 74 68 65 20 63 6f 6d 70 75 74 65 72 27 |om the computer'| 00000a50 73 20 33 32 4b 20 52 41 4d 20 66 6f 72 20 61 20 |s 32K RAM for a | 00000a60 4d 4f 44 45 20 32 20 73 63 72 65 65 6e 2e 20 49 |MODE 2 screen. I| 00000a70 66 20 74 68 69 73 20 69 73 20 74 68 65 20 63 61 |f this is the ca| 00000a80 73 65 2c 0d 79 6f 75 20 6d 75 73 74 20 75 73 65 |se,.you must use| 00000a90 20 61 20 6d 6f 64 65 20 77 68 69 63 68 20 75 73 | a mode which us| 00000aa0 65 73 20 6c 65 73 73 20 6d 65 6d 6f 72 79 2c 20 |es less memory, | 00000ab0 73 75 63 68 20 61 73 20 6d 6f 64 65 20 35 2e 0d |such as mode 5..| 00000ac0 0d 20 20 20 20 20 4d 79 20 61 64 76 69 63 65 20 |. My advice | 00000ad0 69 6e 20 63 68 6f 6f 73 69 6e 67 20 77 68 69 63 |in choosing whic| 00000ae0 68 20 6d 6f 64 65 20 74 6f 20 75 73 65 20 77 6f |h mode to use wo| 00000af0 75 6c 64 20 62 65 20 74 6f 20 74 72 79 2c 20 69 |uld be to try, i| 00000b00 66 20 61 74 20 61 6c 6c 0d 70 6f 73 73 69 62 6c |f at all.possibl| 00000b10 65 2c 20 74 6f 20 75 73 65 20 6f 6e 65 20 6f 66 |e, to use one of| 00000b20 20 74 68 65 20 32 30 4b 20 6d 6f 64 65 73 2e 20 | the 20K modes. | 00000b30 54 68 65 20 64 65 74 61 69 6c 20 6f 66 20 4d 4f |The detail of MO| 00000b40 44 45 20 31 2c 20 61 6e 64 20 74 68 65 0d 63 6f |DE 1, and the.co| 00000b50 6c 6f 75 72 73 20 6f 66 20 4d 4f 44 45 20 32 2c |lours of MODE 2,| 00000b60 20 61 72 65 20 62 6f 74 68 20 66 61 72 20 73 75 | are both far su| 00000b70 70 65 72 69 6f 72 20 74 6f 20 74 68 65 20 71 75 |perior to the qu| 00000b80 61 6c 69 74 79 20 6f 66 20 4d 4f 44 45 20 35 2e |ality of MODE 5.| 00000b90 20 49 66 20 79 6f 75 0d 61 72 65 20 61 6e 20 65 | If you.are an e| 00000ba0 66 66 69 63 69 65 6e 74 20 70 72 6f 67 72 61 6d |fficient program| 00000bb0 6d 65 72 2c 20 79 6f 75 20 73 68 6f 75 6c 64 20 |mer, you should | 00000bc0 66 69 6e 64 20 74 68 61 74 20 69 74 20 69 73 20 |find that it is | 00000bd0 70 65 72 66 65 63 74 6c 79 20 0d 70 6f 73 73 69 |perfectly .possi| 00000be0 62 6c 65 20 74 6f 20 66 69 74 20 61 20 72 65 61 |ble to fit a rea| 00000bf0 73 6f 6e 61 62 6c 79 20 6c 65 6e 67 74 68 65 64 |sonably lengthed| 00000c00 20 70 72 6f 67 72 61 6d 20 69 6e 74 6f 20 6d 65 | program into me| 00000c10 6d 6f 72 79 20 61 74 20 74 68 65 20 73 61 6d 65 |mory at the same| 00000c20 20 0d 74 69 6d 65 20 61 73 20 32 30 4b 20 6f 66 | .time as 20K of| 00000c30 20 73 63 72 65 65 6e 2e 20 53 68 69 70 77 72 65 | screen. Shipwre| 00000c40 63 6b 65 64 2c 20 66 6f 72 20 65 78 61 6d 70 6c |cked, for exampl| 00000c50 65 2c 20 75 73 65 64 20 4d 4f 44 45 20 32 20 66 |e, used MODE 2 f| 00000c60 6f 72 20 69 74 73 20 0d 67 72 61 70 68 69 63 73 |or its .graphics| 00000c70 2c 20 61 73 20 64 6f 65 73 20 53 68 69 70 77 72 |, as does Shipwr| 00000c80 65 63 6b 65 64 20 49 49 20 6f 6e 20 74 68 69 73 |ecked II on this| 00000c90 20 69 73 73 75 65 2e 0d 20 20 20 20 20 46 69 74 | issue.. Fit| 00000ca0 74 69 6e 67 20 61 20 70 72 6f 67 72 61 6d 20 69 |ting a program i| 00000cb0 6e 74 6f 20 6d 65 6d 6f 72 79 20 61 73 20 77 65 |nto memory as we| 00000cc0 6c 6c 20 61 73 20 61 20 6c 61 72 67 65 20 73 63 |ll as a large sc| 00000cd0 72 65 65 6e 20 6d 65 6d 6f 72 79 20 69 73 20 0d |reen memory is .| 00000ce0 66 61 69 72 6c 79 20 65 61 73 79 20 77 68 65 6e |fairly easy when| 00000cf0 20 79 6f 75 20 61 72 65 20 75 73 69 6e 67 20 61 | you are using a| 00000d00 20 74 61 70 65 20 6f 72 20 44 46 53 20 66 69 6c | tape or DFS fil| 00000d10 69 6e 67 20 73 79 73 74 65 6d 2c 20 62 75 74 20 |ing system, but | 00000d20 74 68 69 73 20 63 61 6e 0d 70 72 6f 76 65 20 64 |this can.prove d| 00000d30 69 66 66 69 63 75 6c 74 20 77 69 74 68 20 41 44 |ifficult with AD| 00000d40 46 53 2c 20 62 65 63 61 75 73 65 20 34 4b 20 6f |FS, because 4K o| 00000d50 66 20 74 68 65 20 6d 65 6d 6f 72 79 20 6e 6f 72 |f the memory nor| 00000d60 6d 61 6c 6c 79 20 75 73 65 64 20 74 6f 0d 73 74 |mally used to.st| 00000d70 6f 72 65 20 70 72 6f 67 72 61 6d 73 20 69 73 20 |ore programs is | 00000d80 74 61 6b 65 6e 20 61 77 61 79 20 66 6f 72 20 74 |taken away for t| 00000d90 68 65 20 41 44 46 53 20 74 6f 20 75 73 65 2c 20 |he ADFS to use, | 00000da0 6c 65 61 76 69 6e 67 20 79 6f 75 20 6f 6e 6c 79 |leaving you only| 00000db0 20 61 20 6d 65 72 65 0d 34 2e 35 4b 20 66 72 65 | a mere.4.5K fre| 00000dc0 65 20 66 6f 72 20 70 72 6f 67 72 61 6d 73 2e 20 |e for programs. | 00000dd0 41 73 73 75 6d 69 6e 67 20 74 68 61 74 20 6f 6e |Assuming that on| 00000de0 63 65 20 79 6f 75 20 68 61 76 65 20 6c 6f 61 64 |ce you have load| 00000df0 65 64 20 74 68 65 20 70 72 6f 67 72 61 6d 0d 79 |ed the program.y| 00000e00 6f 75 20 64 6f 20 6e 6f 74 20 69 6e 74 65 6e 64 |ou do not intend| 00000e10 20 74 6f 20 75 73 65 20 74 68 65 20 64 69 73 6b | to use the disk| 00000e20 20 61 67 61 69 6e 2c 20 74 68 65 72 65 20 69 73 | again, there is| 00000e30 20 61 20 77 61 79 20 61 72 6f 75 6e 64 20 74 68 | a way around th| 00000e40 69 73 2e 20 49 66 0d 79 6f 75 20 73 77 69 74 63 |is. If.you switc| 00000e50 68 20 6f 76 65 72 20 74 6f 20 61 20 74 61 70 65 |h over to a tape| 00000e60 20 66 69 6c 69 6e 67 20 73 79 73 74 65 6d 2c 20 | filing system, | 00000e70 74 68 65 20 41 44 46 53 20 6d 65 6d 6f 72 79 20 |the ADFS memory | 00000e80 62 65 63 6f 6d 65 73 20 0d 72 65 64 75 6e 64 61 |becomes .redunda| 00000e90 6e 74 20 61 6e 64 20 63 61 6e 20 62 65 20 72 65 |nt and can be re| 00000ea0 63 6c 61 69 6d 65 64 20 66 6f 72 20 42 41 53 49 |claimed for BASI| 00000eb0 43 20 75 73 65 2e 20 4f 6e 63 65 20 79 6f 75 20 |C use. Once you | 00000ec0 68 61 76 65 20 64 6f 6e 65 20 74 68 69 73 2c 20 |have done this, | 00000ed0 6f 66 20 0d 63 6f 75 72 73 65 2c 20 79 6f 75 20 |of .course, you | 00000ee0 63 61 6e 6e 6f 74 20 61 63 63 65 73 73 20 64 69 |cannot access di| 00000ef0 73 6b 73 20 77 69 74 68 6f 75 74 20 72 65 73 65 |sks without rese| 00000f00 74 74 69 6e 67 20 74 68 65 20 63 6f 6d 70 75 74 |tting the comput| 00000f10 65 72 2c 20 73 6f 20 6c 6f 61 64 20 0d 61 6e 64 |er, so load .and| 00000f20 20 73 61 76 65 20 6f 70 74 69 6f 6e 73 20 69 6e | save options in| 00000f30 20 79 6f 75 72 20 70 72 6f 67 72 61 6d 20 61 72 | your program ar| 00000f40 65 20 72 65 73 74 72 69 63 74 65 64 20 74 6f 20 |e restricted to | 00000f50 74 61 70 65 20 6f 6e 6c 79 2e 20 54 68 69 73 20 |tape only. This | 00000f60 0d 74 65 63 68 6e 69 71 75 65 20 77 69 6c 6c 20 |.technique will | 00000f70 62 65 20 65 78 70 6c 61 69 6e 65 64 20 69 6e 20 |be explained in | 00000f80 67 72 65 61 74 65 72 20 64 65 70 74 68 20 69 6e |greater depth in| 00000f90 20 61 20 6c 61 74 65 72 20 61 72 74 69 63 6c 65 | a later article| 00000fa0 20 6f 6e 20 6d 65 6d 6f 72 79 0d 6d 61 6e 61 67 | on memory.manag| 00000fb0 65 6d 65 6e 74 2e 0d |ement..| 00000fb7
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