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+PT1
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 » Archimedes » Unlabelled_disk_2.ADF |
| Filename: | +PT1 |
| Read OK: | ✔ |
| File size: | 1288 bytes |
| Load address: | 2B206576 |
| Exec address: | D315450 |
Duplicates
There is 1 duplicate copy of this file in the archive:
- Personal collection » Acorn ADFS disks » Archimedes » Unlabelled_disk_2.ADF » +PT1
- Personal collection » Acorn hard disk » misc » misc3 » shipwren/+PT1
File contents
PROGRAMMING TECHNIQUE
by Dominic Ford
Part 1: Designing a program
In this series, I shall be showing you how to use your programming
skills to achieve the best results that you can. I will assume that you
can already program, at least in BASIC. If you cannot do so, you need to
read either the User Guide's BASIC tutorial, or even better, a book such
as "The Electron Book", which provides an excellent tutorial. Similarly,
if you want to learn assembly language, you need a book such as "Electron
Assembly Language" (Shiva), which provides a much better tutorial than EUG
could ever provide, simply because no reader has enough time to write such
a detailed tutorial, and besides, there is not enough room on EUG to
publish such a long article.
If you have any ideas for subjects that you want me to cover in
Programming Technique, please do write into EUG and tell me about them. I
already have plans for articles on graphics, sound, and memory mangement.
Do you want details about any writing specific type of program? If you
prefer using email to sending comments into EUG, I have a temporary
address, which is: "dominic@reigram.demon.co.uk"
So, you have an idea for a program which you want to write. The
first thing to do, before you start writing any code, is to visualise what
the user will see and do when they use the program. If it is a game,
imagine what the user will have to do, and what they will see on screen as
they do it. Forget the title screen and introduction: these are fun to
write, and although the user will see them first, before the actual
program, you should program them last. Concentrate on the heart of the
program first. You may have some important decisions to make. For example
in an arcade adventure such as Shipwrecked, you must decide whether it is
to scroll, or whether it is to be a flick screen game (like the original
Shipwrecked).
Next, you should start to plan out how the computer will achieve
these results. Sketches are often a good idea, to show the flow of the
program from one routine to another. One great decision which you must
make is whether to use BASIC or machine code. If speed is important,
machine code is useful, but if readability or ease of writing the code is
important, BASIC is a good choice. A mixture can also be good in some
circumstances. You may want to do the main body of the code in BASIC,
where it is easily readable, and quick to write, and have the slower
routines in machine code. Animation routines, for example, may need
machine code for speed. Laser Darts is an example of such a program. I
wrote the main loop in BASIC, but the animation of the laser is too slow
for BASIC, so I did it in machine code. When the player fires a laser, I
simply execute CALLlaser.
But do not start any coding yet - your routines should stay simply as
names in boxes for the moment. Your plans do not have to be that clear -
in fact if they are too clear cut you may have problems if you cannot
achieve quite the effect you want. You should leave room to make
alterations if you cannot get the computer to produce the right effect, or
simply if you discover a much better effect than the one you originally
planned! Often effects which you think will be really good in fact looks
or sounds dreadful in practise. On the other hand often the best effects
are stumbled upon quite by accident.
Now is the time to start programming. Pick one, and only one, of
the routines on your diagram, and then write the code for that routine. It
is very important that you do not code too much at any one go. Your
program should start out very simple, and slowly work up to being
something complex. You may even want to start with only half a routine,
but whatever it is you need to be able to test it to ensure that it works
faultlessly.
When you start testing your routine, make sure that you save the
program or source code first - the computer may well crash, in which case
you could very easily lose your work. Do not be afraid to risk crashing
the computer - test the routine as vigorously as possible. For example, if
you are writing a routine to find the square root of a number, ask it what
the root of -2 is (there is not one). Is the result acceptable? If not,
fix it. Remember, if you ask for a number between 1 and 10, some user is
bound to type 11, and your program should be prepared to deal with this.
Even internal routines should check to see if they are called with illegal
parameters. If a routine is called with the wrong parameters, it is much
easier to trace the problem if your program says "ERROR AT 100" than if it
simply does not operate in the way it should.
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 20 62 79 20 44 6f | by Do| 00000050 6d 69 6e 69 63 20 46 6f 72 64 0d 20 20 20 20 20 |minic Ford. | 00000060 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00000070 20 50 61 72 74 20 31 3a 20 44 65 73 69 67 6e 69 | Part 1: Designi| 00000080 6e 67 20 61 20 70 72 6f 67 72 61 6d 0d 0d 20 20 |ng a program.. | 00000090 20 20 20 49 6e 20 74 68 69 73 20 73 65 72 69 65 | In this serie| 000000a0 73 2c 20 49 20 73 68 61 6c 6c 20 62 65 20 73 68 |s, I shall be sh| 000000b0 6f 77 69 6e 67 20 79 6f 75 20 68 6f 77 20 74 6f |owing you how to| 000000c0 20 75 73 65 20 79 6f 75 72 20 70 72 6f 67 72 61 | use your progra| 000000d0 6d 6d 69 6e 67 0d 73 6b 69 6c 6c 73 20 74 6f 20 |mming.skills to | 000000e0 61 63 68 69 65 76 65 20 74 68 65 20 62 65 73 74 |achieve the best| 000000f0 20 72 65 73 75 6c 74 73 20 74 68 61 74 20 79 6f | results that yo| 00000100 75 20 63 61 6e 2e 20 49 20 77 69 6c 6c 20 61 73 |u can. I will as| 00000110 73 75 6d 65 20 74 68 61 74 20 79 6f 75 0d 63 61 |sume that you.ca| 00000120 6e 20 61 6c 72 65 61 64 79 20 70 72 6f 67 72 61 |n already progra| 00000130 6d 2c 20 61 74 20 6c 65 61 73 74 20 69 6e 20 42 |m, at least in B| 00000140 41 53 49 43 2e 20 49 66 20 79 6f 75 20 63 61 6e |ASIC. If you can| 00000150 6e 6f 74 20 64 6f 20 73 6f 2c 20 79 6f 75 20 6e |not do so, you n| 00000160 65 65 64 20 74 6f 0d 72 65 61 64 20 65 69 74 68 |eed to.read eith| 00000170 65 72 20 74 68 65 20 55 73 65 72 20 47 75 69 64 |er the User Guid| 00000180 65 27 73 20 42 41 53 49 43 20 74 75 74 6f 72 69 |e's BASIC tutori| 00000190 61 6c 2c 20 6f 72 20 65 76 65 6e 20 62 65 74 74 |al, or even bett| 000001a0 65 72 2c 20 61 20 62 6f 6f 6b 20 73 75 63 68 0d |er, a book such.| 000001b0 61 73 20 22 54 68 65 20 45 6c 65 63 74 72 6f 6e |as "The Electron| 000001c0 20 42 6f 6f 6b 22 2c 20 77 68 69 63 68 20 70 72 | Book", which pr| 000001d0 6f 76 69 64 65 73 20 61 6e 20 65 78 63 65 6c 6c |ovides an excell| 000001e0 65 6e 74 20 74 75 74 6f 72 69 61 6c 2e 20 53 69 |ent tutorial. Si| 000001f0 6d 69 6c 61 72 6c 79 2c 0d 69 66 20 79 6f 75 20 |milarly,.if you | 00000200 77 61 6e 74 20 74 6f 20 6c 65 61 72 6e 20 61 73 |want to learn as| 00000210 73 65 6d 62 6c 79 20 6c 61 6e 67 75 61 67 65 2c |sembly language,| 00000220 20 79 6f 75 20 6e 65 65 64 20 61 20 62 6f 6f 6b | you need a book| 00000230 20 73 75 63 68 20 61 73 20 22 45 6c 65 63 74 72 | such as "Electr| 00000240 6f 6e 0d 41 73 73 65 6d 62 6c 79 20 4c 61 6e 67 |on.Assembly Lang| 00000250 75 61 67 65 22 20 28 53 68 69 76 61 29 2c 20 77 |uage" (Shiva), w| 00000260 68 69 63 68 20 70 72 6f 76 69 64 65 73 20 61 20 |hich provides a | 00000270 6d 75 63 68 20 62 65 74 74 65 72 20 74 75 74 6f |much better tuto| 00000280 72 69 61 6c 20 74 68 61 6e 20 45 55 47 0d 63 6f |rial than EUG.co| 00000290 75 6c 64 20 65 76 65 72 20 70 72 6f 76 69 64 65 |uld ever provide| 000002a0 2c 20 73 69 6d 70 6c 79 20 62 65 63 61 75 73 65 |, simply because| 000002b0 20 6e 6f 20 72 65 61 64 65 72 20 68 61 73 20 65 | no reader has e| 000002c0 6e 6f 75 67 68 20 74 69 6d 65 20 74 6f 20 77 72 |nough time to wr| 000002d0 69 74 65 20 73 75 63 68 0d 61 20 64 65 74 61 69 |ite such.a detai| 000002e0 6c 65 64 20 74 75 74 6f 72 69 61 6c 2c 20 61 6e |led tutorial, an| 000002f0 64 20 62 65 73 69 64 65 73 2c 20 74 68 65 72 65 |d besides, there| 00000300 20 69 73 20 6e 6f 74 20 65 6e 6f 75 67 68 20 72 | is not enough r| 00000310 6f 6f 6d 20 6f 6e 20 45 55 47 20 74 6f 0d 70 75 |oom on EUG to.pu| 00000320 62 6c 69 73 68 20 73 75 63 68 20 61 20 6c 6f 6e |blish such a lon| 00000330 67 20 61 72 74 69 63 6c 65 2e 0d 20 20 20 20 20 |g article.. | 00000340 49 66 20 79 6f 75 20 68 61 76 65 20 61 6e 79 20 |If you have any | 00000350 69 64 65 61 73 20 66 6f 72 20 73 75 62 6a 65 63 |ideas for subjec| 00000360 74 73 20 74 68 61 74 20 79 6f 75 20 77 61 6e 74 |ts that you want| 00000370 20 6d 65 20 74 6f 20 63 6f 76 65 72 20 69 6e 0d | me to cover in.| 00000380 50 72 6f 67 72 61 6d 6d 69 6e 67 20 54 65 63 68 |Programming Tech| 00000390 6e 69 71 75 65 2c 20 70 6c 65 61 73 65 20 64 6f |nique, please do| 000003a0 20 77 72 69 74 65 20 69 6e 74 6f 20 45 55 47 20 | write into EUG | 000003b0 61 6e 64 20 74 65 6c 6c 20 6d 65 20 61 62 6f 75 |and tell me abou| 000003c0 74 20 74 68 65 6d 2e 20 49 0d 61 6c 72 65 61 64 |t them. I.alread| 000003d0 79 20 68 61 76 65 20 70 6c 61 6e 73 20 66 6f 72 |y have plans for| 000003e0 20 61 72 74 69 63 6c 65 73 20 6f 6e 20 67 72 61 | articles on gra| 000003f0 70 68 69 63 73 2c 20 73 6f 75 6e 64 2c 20 61 6e |phics, sound, an| 00000400 64 20 6d 65 6d 6f 72 79 20 6d 61 6e 67 65 6d 65 |d memory mangeme| 00000410 6e 74 2e 0d 44 6f 20 79 6f 75 20 77 61 6e 74 20 |nt..Do you want | 00000420 64 65 74 61 69 6c 73 20 61 62 6f 75 74 20 61 6e |details about an| 00000430 79 20 77 72 69 74 69 6e 67 20 73 70 65 63 69 66 |y writing specif| 00000440 69 63 20 74 79 70 65 20 6f 66 20 70 72 6f 67 72 |ic type of progr| 00000450 61 6d 3f 20 49 66 20 79 6f 75 0d 70 72 65 66 65 |am? If you.prefe| 00000460 72 20 75 73 69 6e 67 20 65 6d 61 69 6c 20 74 6f |r using email to| 00000470 20 73 65 6e 64 69 6e 67 20 63 6f 6d 6d 65 6e 74 | sending comment| 00000480 73 20 69 6e 74 6f 20 45 55 47 2c 20 49 20 68 61 |s into EUG, I ha| 00000490 76 65 20 61 20 74 65 6d 70 6f 72 61 72 79 0d 61 |ve a temporary.a| 000004a0 64 64 72 65 73 73 2c 20 77 68 69 63 68 20 69 73 |ddress, which is| 000004b0 3a 20 22 64 6f 6d 69 6e 69 63 40 72 65 69 67 72 |: "dominic@reigr| 000004c0 61 6d 2e 64 65 6d 6f 6e 2e 63 6f 2e 75 6b 22 0d |am.demon.co.uk".| 000004d0 20 20 20 20 20 53 6f 2c 20 79 6f 75 20 68 61 76 | So, you hav| 000004e0 65 20 61 6e 20 69 64 65 61 20 66 6f 72 20 61 20 |e an idea for a | 000004f0 70 72 6f 67 72 61 6d 20 77 68 69 63 68 20 79 6f |program which yo| 00000500 75 20 77 61 6e 74 20 74 6f 20 77 72 69 74 65 2e |u want to write.| 00000510 20 54 68 65 0d 66 69 72 73 74 20 74 68 69 6e 67 | The.first thing| 00000520 20 74 6f 20 64 6f 2c 20 62 65 66 6f 72 65 20 79 | to do, before y| 00000530 6f 75 20 73 74 61 72 74 20 77 72 69 74 69 6e 67 |ou start writing| 00000540 20 61 6e 79 20 63 6f 64 65 2c 20 69 73 20 74 6f | any code, is to| 00000550 20 76 69 73 75 61 6c 69 73 65 20 77 68 61 74 0d | visualise what.| 00000560 74 68 65 20 75 73 65 72 20 77 69 6c 6c 20 73 65 |the user will se| 00000570 65 20 61 6e 64 20 64 6f 20 77 68 65 6e 20 74 68 |e and do when th| 00000580 65 79 20 75 73 65 20 74 68 65 20 70 72 6f 67 72 |ey use the progr| 00000590 61 6d 2e 20 49 66 20 69 74 20 69 73 20 61 20 67 |am. If it is a g| 000005a0 61 6d 65 2c 0d 69 6d 61 67 69 6e 65 20 77 68 61 |ame,.imagine wha| 000005b0 74 20 74 68 65 20 75 73 65 72 20 77 69 6c 6c 20 |t the user will | 000005c0 68 61 76 65 20 74 6f 20 64 6f 2c 20 61 6e 64 20 |have to do, and | 000005d0 77 68 61 74 20 74 68 65 79 20 77 69 6c 6c 20 73 |what they will s| 000005e0 65 65 20 6f 6e 20 73 63 72 65 65 6e 20 61 73 0d |ee on screen as.| 000005f0 74 68 65 79 20 64 6f 20 69 74 2e 20 46 6f 72 67 |they do it. Forg| 00000600 65 74 20 74 68 65 20 74 69 74 6c 65 20 73 63 72 |et the title scr| 00000610 65 65 6e 20 61 6e 64 20 69 6e 74 72 6f 64 75 63 |een and introduc| 00000620 74 69 6f 6e 3a 20 74 68 65 73 65 20 61 72 65 20 |tion: these are | 00000630 66 75 6e 20 74 6f 0d 77 72 69 74 65 2c 20 61 6e |fun to.write, an| 00000640 64 20 61 6c 74 68 6f 75 67 68 20 74 68 65 20 75 |d although the u| 00000650 73 65 72 20 77 69 6c 6c 20 73 65 65 20 74 68 65 |ser will see the| 00000660 6d 20 66 69 72 73 74 2c 20 62 65 66 6f 72 65 20 |m first, before | 00000670 74 68 65 20 61 63 74 75 61 6c 0d 70 72 6f 67 72 |the actual.progr| 00000680 61 6d 2c 20 79 6f 75 20 73 68 6f 75 6c 64 20 70 |am, you should p| 00000690 72 6f 67 72 61 6d 20 74 68 65 6d 20 6c 61 73 74 |rogram them last| 000006a0 2e 20 43 6f 6e 63 65 6e 74 72 61 74 65 20 6f 6e |. Concentrate on| 000006b0 20 74 68 65 20 68 65 61 72 74 20 6f 66 20 74 68 | the heart of th| 000006c0 65 0d 70 72 6f 67 72 61 6d 20 66 69 72 73 74 2e |e.program first.| 000006d0 20 59 6f 75 20 6d 61 79 20 68 61 76 65 20 73 6f | You may have so| 000006e0 6d 65 20 69 6d 70 6f 72 74 61 6e 74 20 64 65 63 |me important dec| 000006f0 69 73 69 6f 6e 73 20 74 6f 20 6d 61 6b 65 2e 20 |isions to make. | 00000700 46 6f 72 20 65 78 61 6d 70 6c 65 0d 69 6e 20 61 |For example.in a| 00000710 6e 20 61 72 63 61 64 65 20 61 64 76 65 6e 74 75 |n arcade adventu| 00000720 72 65 20 73 75 63 68 20 61 73 20 53 68 69 70 77 |re such as Shipw| 00000730 72 65 63 6b 65 64 2c 20 79 6f 75 20 6d 75 73 74 |recked, you must| 00000740 20 64 65 63 69 64 65 20 77 68 65 74 68 65 72 20 | decide whether | 00000750 69 74 20 69 73 0d 74 6f 20 73 63 72 6f 6c 6c 2c |it is.to scroll,| 00000760 20 6f 72 20 77 68 65 74 68 65 72 20 69 74 20 69 | or whether it i| 00000770 73 20 74 6f 20 62 65 20 61 20 66 6c 69 63 6b 20 |s to be a flick | 00000780 73 63 72 65 65 6e 20 67 61 6d 65 20 28 6c 69 6b |screen game (lik| 00000790 65 20 74 68 65 20 6f 72 69 67 69 6e 61 6c 0d 53 |e the original.S| 000007a0 68 69 70 77 72 65 63 6b 65 64 29 2e 0d 20 20 20 |hipwrecked).. | 000007b0 20 20 4e 65 78 74 2c 20 79 6f 75 20 73 68 6f 75 | Next, you shou| 000007c0 6c 64 20 73 74 61 72 74 20 74 6f 20 70 6c 61 6e |ld start to plan| 000007d0 20 6f 75 74 20 68 6f 77 20 74 68 65 20 63 6f 6d | out how the com| 000007e0 70 75 74 65 72 20 77 69 6c 6c 20 61 63 68 69 65 |puter will achie| 000007f0 76 65 0d 74 68 65 73 65 20 72 65 73 75 6c 74 73 |ve.these results| 00000800 2e 20 53 6b 65 74 63 68 65 73 20 61 72 65 20 6f |. Sketches are o| 00000810 66 74 65 6e 20 61 20 67 6f 6f 64 20 69 64 65 61 |ften a good idea| 00000820 2c 20 74 6f 20 73 68 6f 77 20 74 68 65 20 66 6c |, to show the fl| 00000830 6f 77 20 6f 66 20 74 68 65 0d 70 72 6f 67 72 61 |ow of the.progra| 00000840 6d 20 66 72 6f 6d 20 6f 6e 65 20 72 6f 75 74 69 |m from one routi| 00000850 6e 65 20 74 6f 20 61 6e 6f 74 68 65 72 2e 20 4f |ne to another. O| 00000860 6e 65 20 67 72 65 61 74 20 64 65 63 69 73 69 6f |ne great decisio| 00000870 6e 20 77 68 69 63 68 20 79 6f 75 20 6d 75 73 74 |n which you must| 00000880 0d 6d 61 6b 65 20 69 73 20 77 68 65 74 68 65 72 |.make is whether| 00000890 20 74 6f 20 75 73 65 20 42 41 53 49 43 20 6f 72 | to use BASIC or| 000008a0 20 6d 61 63 68 69 6e 65 20 63 6f 64 65 2e 20 49 | machine code. I| 000008b0 66 20 73 70 65 65 64 20 69 73 20 69 6d 70 6f 72 |f speed is impor| 000008c0 74 61 6e 74 2c 0d 6d 61 63 68 69 6e 65 20 63 6f |tant,.machine co| 000008d0 64 65 20 69 73 20 75 73 65 66 75 6c 2c 20 62 75 |de is useful, bu| 000008e0 74 20 69 66 20 72 65 61 64 61 62 69 6c 69 74 79 |t if readability| 000008f0 20 6f 72 20 65 61 73 65 20 6f 66 20 77 72 69 74 | or ease of writ| 00000900 69 6e 67 20 74 68 65 20 63 6f 64 65 20 69 73 0d |ing the code is.| 00000910 69 6d 70 6f 72 74 61 6e 74 2c 20 42 41 53 49 43 |important, BASIC| 00000920 20 69 73 20 61 20 67 6f 6f 64 20 63 68 6f 69 63 | is a good choic| 00000930 65 2e 20 41 20 6d 69 78 74 75 72 65 20 63 61 6e |e. A mixture can| 00000940 20 61 6c 73 6f 20 62 65 20 67 6f 6f 64 20 69 6e | also be good in| 00000950 20 73 6f 6d 65 0d 63 69 72 63 75 6d 73 74 61 6e | some.circumstan| 00000960 63 65 73 2e 20 59 6f 75 20 6d 61 79 20 77 61 6e |ces. You may wan| 00000970 74 20 74 6f 20 64 6f 20 74 68 65 20 6d 61 69 6e |t to do the main| 00000980 20 62 6f 64 79 20 6f 66 20 74 68 65 20 63 6f 64 | body of the cod| 00000990 65 20 69 6e 20 42 41 53 49 43 2c 0d 77 68 65 72 |e in BASIC,.wher| 000009a0 65 20 69 74 20 69 73 20 65 61 73 69 6c 79 20 72 |e it is easily r| 000009b0 65 61 64 61 62 6c 65 2c 20 61 6e 64 20 71 75 69 |eadable, and qui| 000009c0 63 6b 20 74 6f 20 77 72 69 74 65 2c 20 61 6e 64 |ck to write, and| 000009d0 20 68 61 76 65 20 74 68 65 20 73 6c 6f 77 65 72 | have the slower| 000009e0 0d 72 6f 75 74 69 6e 65 73 20 69 6e 20 6d 61 63 |.routines in mac| 000009f0 68 69 6e 65 20 63 6f 64 65 2e 20 41 6e 69 6d 61 |hine code. Anima| 00000a00 74 69 6f 6e 20 72 6f 75 74 69 6e 65 73 2c 20 66 |tion routines, f| 00000a10 6f 72 20 65 78 61 6d 70 6c 65 2c 20 6d 61 79 20 |or example, may | 00000a20 6e 65 65 64 0d 6d 61 63 68 69 6e 65 20 63 6f 64 |need.machine cod| 00000a30 65 20 66 6f 72 20 73 70 65 65 64 2e 20 4c 61 73 |e for speed. Las| 00000a40 65 72 20 44 61 72 74 73 20 69 73 20 61 6e 20 65 |er Darts is an e| 00000a50 78 61 6d 70 6c 65 20 6f 66 20 73 75 63 68 20 61 |xample of such a| 00000a60 20 70 72 6f 67 72 61 6d 2e 20 49 0d 77 72 6f 74 | program. I.wrot| 00000a70 65 20 74 68 65 20 6d 61 69 6e 20 6c 6f 6f 70 20 |e the main loop | 00000a80 69 6e 20 42 41 53 49 43 2c 20 62 75 74 20 74 68 |in BASIC, but th| 00000a90 65 20 61 6e 69 6d 61 74 69 6f 6e 20 6f 66 20 74 |e animation of t| 00000aa0 68 65 20 6c 61 73 65 72 20 69 73 20 74 6f 6f 20 |he laser is too | 00000ab0 73 6c 6f 77 0d 66 6f 72 20 42 41 53 49 43 2c 20 |slow.for BASIC, | 00000ac0 73 6f 20 49 20 64 69 64 20 69 74 20 69 6e 20 6d |so I did it in m| 00000ad0 61 63 68 69 6e 65 20 63 6f 64 65 2e 20 57 68 65 |achine code. Whe| 00000ae0 6e 20 74 68 65 20 70 6c 61 79 65 72 20 66 69 72 |n the player fir| 00000af0 65 73 20 61 20 6c 61 73 65 72 2c 20 49 0d 73 69 |es a laser, I.si| 00000b00 6d 70 6c 79 20 65 78 65 63 75 74 65 20 43 41 4c |mply execute CAL| 00000b10 4c 6c 61 73 65 72 2e 0d 20 20 20 20 20 42 75 74 |Llaser.. But| 00000b20 20 64 6f 20 6e 6f 74 20 73 74 61 72 74 20 61 6e | do not start an| 00000b30 79 20 63 6f 64 69 6e 67 20 79 65 74 20 2d 20 79 |y coding yet - y| 00000b40 6f 75 72 20 72 6f 75 74 69 6e 65 73 20 73 68 6f |our routines sho| 00000b50 75 6c 64 20 73 74 61 79 20 73 69 6d 70 6c 79 20 |uld stay simply | 00000b60 61 73 0d 6e 61 6d 65 73 20 69 6e 20 62 6f 78 65 |as.names in boxe| 00000b70 73 20 66 6f 72 20 74 68 65 20 6d 6f 6d 65 6e 74 |s for the moment| 00000b80 2e 20 59 6f 75 72 20 70 6c 61 6e 73 20 64 6f 20 |. Your plans do | 00000b90 6e 6f 74 20 68 61 76 65 20 74 6f 20 62 65 20 74 |not have to be t| 00000ba0 68 61 74 20 63 6c 65 61 72 20 2d 0d 69 6e 20 66 |hat clear -.in f| 00000bb0 61 63 74 20 69 66 20 74 68 65 79 20 61 72 65 20 |act if they are | 00000bc0 74 6f 6f 20 63 6c 65 61 72 20 63 75 74 20 79 6f |too clear cut yo| 00000bd0 75 20 6d 61 79 20 68 61 76 65 20 70 72 6f 62 6c |u may have probl| 00000be0 65 6d 73 20 69 66 20 79 6f 75 20 63 61 6e 6e 6f |ems if you canno| 00000bf0 74 0d 61 63 68 69 65 76 65 20 71 75 69 74 65 20 |t.achieve quite | 00000c00 74 68 65 20 65 66 66 65 63 74 20 79 6f 75 20 77 |the effect you w| 00000c10 61 6e 74 2e 20 59 6f 75 20 73 68 6f 75 6c 64 20 |ant. You should | 00000c20 6c 65 61 76 65 20 72 6f 6f 6d 20 74 6f 20 6d 61 |leave room to ma| 00000c30 6b 65 0d 61 6c 74 65 72 61 74 69 6f 6e 73 20 69 |ke.alterations i| 00000c40 66 20 79 6f 75 20 63 61 6e 6e 6f 74 20 67 65 74 |f you cannot get| 00000c50 20 74 68 65 20 63 6f 6d 70 75 74 65 72 20 74 6f | the computer to| 00000c60 20 70 72 6f 64 75 63 65 20 74 68 65 20 72 69 67 | produce the rig| 00000c70 68 74 20 65 66 66 65 63 74 2c 20 6f 72 0d 73 69 |ht effect, or.si| 00000c80 6d 70 6c 79 20 69 66 20 79 6f 75 20 64 69 73 63 |mply if you disc| 00000c90 6f 76 65 72 20 61 20 6d 75 63 68 20 62 65 74 74 |over a much bett| 00000ca0 65 72 20 65 66 66 65 63 74 20 74 68 61 6e 20 74 |er effect than t| 00000cb0 68 65 20 6f 6e 65 20 79 6f 75 20 6f 72 69 67 69 |he one you origi| 00000cc0 6e 61 6c 6c 79 0d 70 6c 61 6e 6e 65 64 21 20 4f |nally.planned! O| 00000cd0 66 74 65 6e 20 65 66 66 65 63 74 73 20 77 68 69 |ften effects whi| 00000ce0 63 68 20 79 6f 75 20 74 68 69 6e 6b 20 77 69 6c |ch you think wil| 00000cf0 6c 20 62 65 20 72 65 61 6c 6c 79 20 67 6f 6f 64 |l be really good| 00000d00 20 69 6e 20 66 61 63 74 20 6c 6f 6f 6b 73 0d 6f | in fact looks.o| 00000d10 72 20 73 6f 75 6e 64 73 20 64 72 65 61 64 66 75 |r sounds dreadfu| 00000d20 6c 20 69 6e 20 70 72 61 63 74 69 73 65 2e 20 4f |l in practise. O| 00000d30 6e 20 74 68 65 20 6f 74 68 65 72 20 68 61 6e 64 |n the other hand| 00000d40 20 6f 66 74 65 6e 20 74 68 65 20 62 65 73 74 20 | often the best | 00000d50 65 66 66 65 63 74 73 0d 61 72 65 20 73 74 75 6d |effects.are stum| 00000d60 62 6c 65 64 20 75 70 6f 6e 20 71 75 69 74 65 20 |bled upon quite | 00000d70 62 79 20 61 63 63 69 64 65 6e 74 2e 0d 20 20 20 |by accident.. | 00000d80 20 20 4e 6f 77 20 69 73 20 74 68 65 20 74 69 6d | Now is the tim| 00000d90 65 20 74 6f 20 73 74 61 72 74 20 70 72 6f 67 72 |e to start progr| 00000da0 61 6d 6d 69 6e 67 2e 20 50 69 63 6b 20 6f 6e 65 |amming. Pick one| 00000db0 2c 20 61 6e 64 20 6f 6e 6c 79 20 6f 6e 65 2c 20 |, and only one, | 00000dc0 6f 66 0d 74 68 65 20 72 6f 75 74 69 6e 65 73 20 |of.the routines | 00000dd0 6f 6e 20 79 6f 75 72 20 64 69 61 67 72 61 6d 2c |on your diagram,| 00000de0 20 61 6e 64 20 74 68 65 6e 20 77 72 69 74 65 20 | and then write | 00000df0 74 68 65 20 63 6f 64 65 20 66 6f 72 20 74 68 61 |the code for tha| 00000e00 74 20 72 6f 75 74 69 6e 65 2e 20 49 74 0d 69 73 |t routine. It.is| 00000e10 20 76 65 72 79 20 69 6d 70 6f 72 74 61 6e 74 20 | very important | 00000e20 74 68 61 74 20 79 6f 75 20 64 6f 20 6e 6f 74 20 |that you do not | 00000e30 63 6f 64 65 20 74 6f 6f 20 6d 75 63 68 20 61 74 |code too much at| 00000e40 20 61 6e 79 20 6f 6e 65 20 67 6f 2e 20 59 6f 75 | any one go. You| 00000e50 72 0d 70 72 6f 67 72 61 6d 20 73 68 6f 75 6c 64 |r.program should| 00000e60 20 73 74 61 72 74 20 6f 75 74 20 76 65 72 79 20 | start out very | 00000e70 73 69 6d 70 6c 65 2c 20 61 6e 64 20 73 6c 6f 77 |simple, and slow| 00000e80 6c 79 20 77 6f 72 6b 20 75 70 20 74 6f 20 62 65 |ly work up to be| 00000e90 69 6e 67 0d 73 6f 6d 65 74 68 69 6e 67 20 63 6f |ing.something co| 00000ea0 6d 70 6c 65 78 2e 20 59 6f 75 20 6d 61 79 20 65 |mplex. You may e| 00000eb0 76 65 6e 20 77 61 6e 74 20 74 6f 20 73 74 61 72 |ven want to star| 00000ec0 74 20 77 69 74 68 20 6f 6e 6c 79 20 68 61 6c 66 |t with only half| 00000ed0 20 61 20 72 6f 75 74 69 6e 65 2c 0d 62 75 74 20 | a routine,.but | 00000ee0 77 68 61 74 65 76 65 72 20 69 74 20 69 73 20 79 |whatever it is y| 00000ef0 6f 75 20 6e 65 65 64 20 74 6f 20 62 65 20 61 62 |ou need to be ab| 00000f00 6c 65 20 74 6f 20 74 65 73 74 20 69 74 20 74 6f |le to test it to| 00000f10 20 65 6e 73 75 72 65 20 74 68 61 74 20 69 74 20 | ensure that it | 00000f20 77 6f 72 6b 73 0d 66 61 75 6c 74 6c 65 73 73 6c |works.faultlessl| 00000f30 79 2e 0d 20 20 20 20 20 57 68 65 6e 20 79 6f 75 |y.. When you| 00000f40 20 73 74 61 72 74 20 74 65 73 74 69 6e 67 20 79 | start testing y| 00000f50 6f 75 72 20 72 6f 75 74 69 6e 65 2c 20 6d 61 6b |our routine, mak| 00000f60 65 20 73 75 72 65 20 74 68 61 74 20 79 6f 75 20 |e sure that you | 00000f70 73 61 76 65 20 74 68 65 0d 70 72 6f 67 72 61 6d |save the.program| 00000f80 20 6f 72 20 73 6f 75 72 63 65 20 63 6f 64 65 20 | or source code | 00000f90 66 69 72 73 74 20 2d 20 74 68 65 20 63 6f 6d 70 |first - the comp| 00000fa0 75 74 65 72 20 6d 61 79 20 77 65 6c 6c 20 63 72 |uter may well cr| 00000fb0 61 73 68 2c 20 69 6e 20 77 68 69 63 68 20 63 61 |ash, in which ca| 00000fc0 73 65 0d 79 6f 75 20 63 6f 75 6c 64 20 76 65 72 |se.you could ver| 00000fd0 79 20 65 61 73 69 6c 79 20 6c 6f 73 65 20 79 6f |y easily lose yo| 00000fe0 75 72 20 77 6f 72 6b 2e 20 44 6f 20 6e 6f 74 20 |ur work. Do not | 00000ff0 62 65 20 61 66 72 61 69 64 20 74 6f 20 72 69 73 |be afraid to ris| 00001000 6b 20 63 72 61 73 68 69 6e 67 0d 74 68 65 20 63 |k crashing.the c| 00001010 6f 6d 70 75 74 65 72 20 2d 20 74 65 73 74 20 74 |omputer - test t| 00001020 68 65 20 72 6f 75 74 69 6e 65 20 61 73 20 76 69 |he routine as vi| 00001030 67 6f 72 6f 75 73 6c 79 20 61 73 20 70 6f 73 73 |gorously as poss| 00001040 69 62 6c 65 2e 20 46 6f 72 20 65 78 61 6d 70 6c |ible. For exampl| 00001050 65 2c 20 69 66 0d 79 6f 75 20 61 72 65 20 77 72 |e, if.you are wr| 00001060 69 74 69 6e 67 20 61 20 72 6f 75 74 69 6e 65 20 |iting a routine | 00001070 74 6f 20 66 69 6e 64 20 74 68 65 20 73 71 75 61 |to find the squa| 00001080 72 65 20 72 6f 6f 74 20 6f 66 20 61 20 6e 75 6d |re root of a num| 00001090 62 65 72 2c 20 61 73 6b 20 69 74 20 77 68 61 74 |ber, ask it what| 000010a0 0d 74 68 65 20 72 6f 6f 74 20 6f 66 20 2d 32 20 |.the root of -2 | 000010b0 69 73 20 28 74 68 65 72 65 20 69 73 20 6e 6f 74 |is (there is not| 000010c0 20 6f 6e 65 29 2e 20 49 73 20 74 68 65 20 72 65 | one). Is the re| 000010d0 73 75 6c 74 20 61 63 63 65 70 74 61 62 6c 65 3f |sult acceptable?| 000010e0 20 49 66 20 6e 6f 74 2c 0d 66 69 78 20 69 74 2e | If not,.fix it.| 000010f0 20 52 65 6d 65 6d 62 65 72 2c 20 69 66 20 79 6f | Remember, if yo| 00001100 75 20 61 73 6b 20 66 6f 72 20 61 20 6e 75 6d 62 |u ask for a numb| 00001110 65 72 20 62 65 74 77 65 65 6e 20 31 20 61 6e 64 |er between 1 and| 00001120 20 31 30 2c 20 73 6f 6d 65 20 75 73 65 72 20 69 | 10, some user i| 00001130 73 0d 62 6f 75 6e 64 20 74 6f 20 74 79 70 65 20 |s.bound to type | 00001140 31 31 2c 20 61 6e 64 20 79 6f 75 72 20 70 72 6f |11, and your pro| 00001150 67 72 61 6d 20 73 68 6f 75 6c 64 20 62 65 20 70 |gram should be p| 00001160 72 65 70 61 72 65 64 20 74 6f 20 64 65 61 6c 20 |repared to deal | 00001170 77 69 74 68 20 74 68 69 73 2e 0d 45 76 65 6e 20 |with this..Even | 00001180 69 6e 74 65 72 6e 61 6c 20 72 6f 75 74 69 6e 65 |internal routine| 00001190 73 20 73 68 6f 75 6c 64 20 63 68 65 63 6b 20 74 |s should check t| 000011a0 6f 20 73 65 65 20 69 66 20 74 68 65 79 20 61 72 |o see if they ar| 000011b0 65 20 63 61 6c 6c 65 64 20 77 69 74 68 20 69 6c |e called with il| 000011c0 6c 65 67 61 6c 0d 70 61 72 61 6d 65 74 65 72 73 |legal.parameters| 000011d0 2e 20 49 66 20 61 20 72 6f 75 74 69 6e 65 20 69 |. If a routine i| 000011e0 73 20 63 61 6c 6c 65 64 20 77 69 74 68 20 74 68 |s called with th| 000011f0 65 20 77 72 6f 6e 67 20 70 61 72 61 6d 65 74 65 |e wrong paramete| 00001200 72 73 2c 20 69 74 20 69 73 20 6d 75 63 68 0d 65 |rs, it is much.e| 00001210 61 73 69 65 72 20 74 6f 20 74 72 61 63 65 20 74 |asier to trace t| 00001220 68 65 20 70 72 6f 62 6c 65 6d 20 69 66 20 79 6f |he problem if yo| 00001230 75 72 20 70 72 6f 67 72 61 6d 20 73 61 79 73 20 |ur program says | 00001240 22 45 52 52 4f 52 20 41 54 20 31 30 30 22 20 74 |"ERROR AT 100" t| 00001250 68 61 6e 20 69 66 20 69 74 0d 73 69 6d 70 6c 79 |han if it.simply| 00001260 20 64 6f 65 73 20 6e 6f 74 20 6f 70 65 72 61 74 | does not operat| 00001270 65 20 69 6e 20 74 68 65 20 77 61 79 20 69 74 20 |e in the way it | 00001280 73 68 6f 75 6c 64 2e 0d |should..| 00001288
+PT1.m0
+PT1.m1
+PT1.m2
+PT1.m4
+PT1.m5
.