P/+P1

Home » Personal collection » Acorn ADFS disks » Electron_User_Group » EUG_35.ADF » P/+P1

P/+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 ADFS disks » Electron_User_Group » EUG_35.ADF
Filename:	P/+P1
Read OK:	✔
File size:	0FB7 bytes
Load address:	D4556
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

P/+P1.m0

P/+P1.m1

P/+P1.m2

P/+P1.m4

P/+P1.m5

Our privacy policy is here.
Last updated: 28 Jul 2024, 23:31 UTC
Website designed by .