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PT/+P2

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: PT/+P2
Read OK: ✔
File size: 1043 bytes
Load address: 2B0D6576
Exec address: D3250
Duplicates

There are 5 duplicate copies of this file in the archive:

File contents
     After you have decided which mode to use, and so you know how many
colours are available, you must decide what colours these are going to
be. In MODE 2, where you have 16 colours, you have access to all of the
colours available, and so this choice does not affect you. In 4 colour
modes, on the other hand, you only initially have access to black, red,
yellow and white. These are a warm selection of colours, but you might
want a colder selection in your program, or just simply a set of colours
which go well with your screen design. To do this you use the command:

VDU 19,logical colour number,actual colour number,0,0,0

     The logical colour number is the number that you use with the colour
command to select that particular colour. In a four colour mode this must
be between 0 and 3, and in a two colour mode this must be either 0 or 1.
The actual colour number is the number of the colour which you want to
assign to that logical colour. The actual colour numbers are given below:

0-Black               8-Flashing black/white
1-Red                 9-Flashing red/cyan
2-Green              10-Flashing grenn/magenta
3-Yellow             11-Flashing yellow/blue
4-Blue               12-Flashing blue/yellow
5-Magenta (purple)   13-Flashing magenta/green
6-Cyan (light blue)  14-Flashing cyan/red
7-White              15-Flashing white/black

     Looking at the table above, you might wonder what the difference is
between flashing black/white and flashing white/black. If you look at
them both seperately, there is little difference, but if you look at them
together, you see that when one is black the other is white, and vice
versa. So, for example, if you put a logo on the screen with the logo in
colour 8 and the background in colour 15, the screen flashes between
white on black and black on white. To demonstrate this, turn on your
Electron and type:

MODE 6:VDU 19,1,8,0,0,0:VDU 19,0,15,0,0,0

     You can take this further. Four is the maximum number of colours 
allowed on screen at any one time. Therefore for different screens you
can have different selections of colours. The main menu screen might be
in warm colours, and then subsequent menu screens in colder colours. The
changing of these logical colours is called "Palette Switching". You can
go even further and create simple animation using palette switching; an
effect which is called "Colour Cycling". For example, you put a row of
colour 3 above a row of colour 2, with a row of colour 1 below that, and
colour 0 at the base. Initially, you set all logical colours to black.
Then, if you set logical colour 0 to white, the base appears. Now set
logical colour 1 to white as well, the bar moves up the screen. Repeat 
this with colours 2 and 3, and you have a simple animation. This is even
more powerful in MODE 2, where you can go through 16 rows up. This is
demonstrated at the end of the tutorial.
     The swirly effect on the title screen of this issue's title screen
was achieved in this way. The colours black, blue, cyan and white are
cycled through a pattern on the screen in order.
     Having decided which graphics mode you are going to use, and which
colours to have on the screen, you must decide how you are going to get
your graphics onto the screen. There are many methods for producing
graphics, and which you choose depends upon what you want the graphics
for, and what you want them to do (and, of course, your programming
ability). The most obvious is the PRINT command. This is a quick, easy
way of putting text onto the screen. When used with the COLOUR command 
and the TAB(x,y) function, many interesting effects can be achieved. 
These are, however, greatly limited by the fact that only letters can be
displayed on the screen. This limitation may be overcome using user
defined characters (see the Graphics chapter of the User Manual for
details). Even using these characters, however, there are serious 
limitations. They can only use one colour per character, and so even if
you make different characters different colours, your screen will still
appear rather dull. Also, they are difficult to use when dealing with
large areas of the screen.

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00000030  6e 64 20 73 6f 20 79 6f  75 20 6b 6e 6f 77 20 68  |nd so you know h|
00000040  6f 77 20 6d 61 6e 79 0d  63 6f 6c 6f 75 72 73 20  |ow many.colours |
00000050  61 72 65 20 61 76 61 69  6c 61 62 6c 65 2c 20 79  |are available, y|
00000060  6f 75 20 6d 75 73 74 20  64 65 63 69 64 65 20 77  |ou must decide w|
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00000170  20 77 68 69 74 65 2e 20  54 68 65 73 65 20 61 72  | white. These ar|
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00000270  30 2c 30 2c 30 0d 0d 20  20 20 20 20 54 68 65 20  |0,0,0..     The |
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000002f0  66 6f 75 72 20 63 6f 6c  6f 75 72 20 6d 6f 64 65  |four colour mode|
00000300  20 74 68 69 73 20 6d 75  73 74 0d 62 65 20 62 65  | this must.be be|
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00000350  20 31 2e 0d 54 68 65 20  61 63 74 75 61 6c 20 63  | 1..The actual c|
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000003e0  6c 6f 77 3a 0d 0d 30 2d  42 6c 61 63 6b 20 20 20  |low:..0-Black   |
000003f0  20 20 20 20 20 20 20 20  20 20 20 20 38 2d 46 6c  |            8-Fl|
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00000410  74 65 0d 31 2d 52 65 64  20 20 20 20 20 20 20 20  |te.1-Red        |
00000420  20 20 20 20 20 20 20 20  20 39 2d 46 6c 61 73 68  |         9-Flash|
00000430  69 6e 67 20 72 65 64 2f  63 79 61 6e 0d 32 2d 47  |ing red/cyan.2-G|
00000440  72 65 65 6e 20 20 20 20  20 20 20 20 20 20 20 20  |reen            |
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00000470  6c 6c 6f 77 20 20 20 20  20 20 20 20 20 20 20 20  |llow            |
00000480  20 31 31 2d 46 6c 61 73  68 69 6e 67 20 79 65 6c  | 11-Flashing yel|
00000490  6c 6f 77 2f 62 6c 75 65  0d 34 2d 42 6c 75 65 20  |low/blue.4-Blue |
000004a0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 31 32  |              12|
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00000520  2d 57 68 69 74 65 20 20  20 20 20 20 20 20 20 20  |-White          |
00000530  20 20 20 20 31 35 2d 46  6c 61 73 68 69 6e 67 20  |    15-Flashing |
00000540  77 68 69 74 65 2f 62 6c  61 63 6b 0d 0d 20 20 20  |white/black..   |
00000550  20 20 4c 6f 6f 6b 69 6e  67 20 61 74 20 74 68 65  |  Looking at the|
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000005e0  20 62 6f 74 68 20 73 65  70 65 72 61 74 65 6c 79  | both seperately|
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00000720  64 65 6d 6f 6e 73 74 72  61 74 65 20 74 68 69 73  |demonstrate this|
00000730  2c 20 74 75 72 6e 20 6f  6e 20 79 6f 75 72 0d 45  |, turn on your.E|
00000740  6c 65 63 74 72 6f 6e 20  61 6e 64 20 74 79 70 65  |lectron and type|
00000750  3a 0d 0d 4d 4f 44 45 20  36 3a 56 44 55 20 31 39  |:..MODE 6:VDU 19|
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00000870  62 73 65 71 75 65 6e 74  20 6d 65 6e 75 20 73 63  |bsequent menu sc|
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00000a30  20 74 68 65 20 62 61 73  65 20 61 70 70 65 61 72  | the base appear|
00000a40  73 2e 20 4e 6f 77 20 73  65 74 0d 6c 6f 67 69 63  |s. Now set.logic|
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00000a60  68 69 74 65 20 61 73 20  77 65 6c 6c 2c 20 74 68  |hite as well, th|
00000a70  65 20 62 61 72 20 6d 6f  76 65 73 20 75 70 20 74  |e bar moves up t|
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00000ad0  68 69 73 20 69 73 20 65  76 65 6e 0d 6d 6f 72 65  |his is even.more|
00000ae0  20 70 6f 77 65 72 66 75  6c 20 69 6e 20 4d 4f 44  | powerful in MOD|
00000af0  45 20 32 2c 20 77 68 65  72 65 20 79 6f 75 20 63  |E 2, where you c|
00000b00  61 6e 20 67 6f 20 74 68  72 6f 75 67 68 20 31 36  |an go through 16|
00000b10  20 72 6f 77 73 20 75 70  2e 20 54 68 69 73 20 69  | rows up. This i|
00000b20  73 0d 64 65 6d 6f 6e 73  74 72 61 74 65 64 20 61  |s.demonstrated a|
00000b30  74 20 74 68 65 20 65 6e  64 20 6f 66 20 74 68 65  |t the end of the|
00000b40  20 74 75 74 6f 72 69 61  6c 2e 0d 20 20 20 20 20  | tutorial..     |
00000b50  54 68 65 20 73 77 69 72  6c 79 20 65 66 66 65 63  |The swirly effec|
00000b60  74 20 6f 6e 20 74 68 65  20 74 69 74 6c 65 20 73  |t on the title s|
00000b70  63 72 65 65 6e 20 6f 66  20 74 68 69 73 20 69 73  |creen of this is|
00000b80  73 75 65 27 73 20 74 69  74 6c 65 20 73 63 72 65  |sue's title scre|
00000b90  65 6e 0d 77 61 73 20 61  63 68 69 65 76 65 64 20  |en.was achieved |
00000ba0  69 6e 20 74 68 69 73 20  77 61 79 2e 20 54 68 65  |in this way. The|
00000bb0  20 63 6f 6c 6f 75 72 73  20 62 6c 61 63 6b 2c 20  | colours black, |
00000bc0  62 6c 75 65 2c 20 63 79  61 6e 20 61 6e 64 20 77  |blue, cyan and w|
00000bd0  68 69 74 65 20 61 72 65  0d 63 79 63 6c 65 64 20  |hite are.cycled |
00000be0  74 68 72 6f 75 67 68 20  61 20 70 61 74 74 65 72  |through a patter|
00000bf0  6e 20 6f 6e 20 74 68 65  20 73 63 72 65 65 6e 20  |n on the screen |
00000c00  69 6e 20 6f 72 64 65 72  2e 0d 20 20 20 20 20 48  |in order..     H|
00000c10  61 76 69 6e 67 20 64 65  63 69 64 65 64 20 77 68  |aving decided wh|
00000c20  69 63 68 20 67 72 61 70  68 69 63 73 20 6d 6f 64  |ich graphics mod|
00000c30  65 20 79 6f 75 20 61 72  65 20 67 6f 69 6e 67 20  |e you are going |
00000c40  74 6f 20 75 73 65 2c 20  61 6e 64 20 77 68 69 63  |to use, and whic|
00000c50  68 0d 63 6f 6c 6f 75 72  73 20 74 6f 20 68 61 76  |h.colours to hav|
00000c60  65 20 6f 6e 20 74 68 65  20 73 63 72 65 65 6e 2c  |e on the screen,|
00000c70  20 79 6f 75 20 6d 75 73  74 20 64 65 63 69 64 65  | you must decide|
00000c80  20 68 6f 77 20 79 6f 75  20 61 72 65 20 67 6f 69  | how you are goi|
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00000d30  61 74 20 79 6f 75 20 77  61 6e 74 20 74 68 65 6d  |at you want them|
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00000d50  63 6f 75 72 73 65 2c 20  79 6f 75 72 20 70 72 6f  |course, your pro|
00000d60  67 72 61 6d 6d 69 6e 67  0d 61 62 69 6c 69 74 79  |gramming.ability|
00000d70  29 2e 20 54 68 65 20 6d  6f 73 74 20 6f 62 76 69  |). The most obvi|
00000d80  6f 75 73 20 69 73 20 74  68 65 20 50 52 49 4e 54  |ous is the PRINT|
00000d90  20 63 6f 6d 6d 61 6e 64  2e 20 54 68 69 73 20 69  | command. This i|
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00000df0  6f 6d 6d 61 6e 64 20 0d  61 6e 64 20 74 68 65 20  |ommand .and the |
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00000e50  2c 20 67 72 65 61 74 6c  79 20 6c 69 6d 69 74 65  |, greatly limite|
00000e60  64 20 62 79 20 74 68 65  20 66 61 63 74 20 74 68  |d by the fact th|
00000e70  61 74 20 6f 6e 6c 79 20  6c 65 74 74 65 72 73 20  |at only letters |
00000e80  63 61 6e 20 62 65 0d 64  69 73 70 6c 61 79 65 64  |can be.displayed|
00000e90  20 6f 6e 20 74 68 65 20  73 63 72 65 65 6e 2e 20  | on the screen. |
00000ea0  54 68 69 73 20 6c 69 6d  69 74 61 74 69 6f 6e 20  |This limitation |
00000eb0  6d 61 79 20 62 65 20 6f  76 65 72 63 6f 6d 65 20  |may be overcome |
00000ec0  75 73 69 6e 67 20 75 73  65 72 0d 64 65 66 69 6e  |using user.defin|
00000ed0  65 64 20 63 68 61 72 61  63 74 65 72 73 20 28 73  |ed characters (s|
00000ee0  65 65 20 74 68 65 20 47  72 61 70 68 69 63 73 20  |ee the Graphics |
00000ef0  63 68 61 70 74 65 72 20  6f 66 20 74 68 65 20 55  |chapter of the U|
00000f00  73 65 72 20 4d 61 6e 75  61 6c 20 66 6f 72 0d 64  |ser Manual for.d|
00000f10  65 74 61 69 6c 73 29 2e  20 45 76 65 6e 20 75 73  |etails). Even us|
00000f20  69 6e 67 20 74 68 65 73  65 20 63 68 61 72 61 63  |ing these charac|
00000f30  74 65 72 73 2c 20 68 6f  77 65 76 65 72 2c 20 74  |ters, however, t|
00000f40  68 65 72 65 20 61 72 65  20 73 65 72 69 6f 75 73  |here are serious|
00000f50  20 0d 6c 69 6d 69 74 61  74 69 6f 6e 73 2e 20 54  | .limitations. T|
00000f60  68 65 79 20 63 61 6e 20  6f 6e 6c 79 20 75 73 65  |hey can only use|
00000f70  20 6f 6e 65 20 63 6f 6c  6f 75 72 20 70 65 72 20  | one colour per |
00000f80  63 68 61 72 61 63 74 65  72 2c 20 61 6e 64 20 73  |character, and s|
00000f90  6f 20 65 76 65 6e 20 69  66 0d 79 6f 75 20 6d 61  |o even if.you ma|
00000fa0  6b 65 20 64 69 66 66 65  72 65 6e 74 20 63 68 61  |ke different cha|
00000fb0  72 61 63 74 65 72 73 20  64 69 66 66 65 72 65 6e  |racters differen|
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00000fe0  6c 0d 61 70 70 65 61 72  20 72 61 74 68 65 72 20  |l.appear rather |
00000ff0  64 75 6c 6c 2e 20 41 6c  73 6f 2c 20 74 68 65 79  |dull. Also, they|
00001000  20 61 72 65 20 64 69 66  66 69 63 75 6c 74 20 74  | are difficult t|
00001010  6f 20 75 73 65 20 77 68  65 6e 20 64 65 61 6c 69  |o use when deali|
00001020  6e 67 20 77 69 74 68 0d  6c 61 72 67 65 20 61 72  |ng with.large ar|
00001030  65 61 73 20 6f 66 20 74  68 65 20 73 63 72 65 65  |eas of the scree|
00001040  6e 2e 0d                                          |n..|
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