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MegaDisc 27 (1992-03)(MegaDisc Digital Publishing)(AU)(Disk 1 of 2)[WB].zip
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MegaDisc 27 (1992-03)(MegaDisc Digital Publishing)(AU)(Disk 1 of 2)[WB].adf
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Hints_&_Tips
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Hints_&_Tips
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1992-03-30
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11KB
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254 lines
HINTS & TIPS
by Tim Strachan
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WHAT ARE RETURN CODES (RC) ?
Return codes are supposed to clarify things, but I'm sure most people have
seen "Prog X did not set a return code" or some such piffle and groaned at
the egregiously computerish nature of it all.
They are designed to let you know if a CLI-launched program (not
Workbench-launched) went well or not for use in Script Files - on the
appearance of a particular RC your script can branch into one of two
possible courses of action.
Here's the interpretation:
RC 0 = All's well
RC 1 to 4 = Perhaps a minor problem, nothing that can't be handled
RC 5 to 9 (WARN) = Struggled through, problems not fatal
RC 10 to 19 (ERROR) = Quite a struggle, just made it
RC 20 or more (FAIL) = Sorry, it fell over and broke.
RC -1 = A secret one which says "never want to hear about this program
again"
So RCs should be built into good programs - Assembly programmers create a
RC value by putting it into register D0 just before ending the program; C
programmers use the function Exit(n) where n= RC value.
A Script File (such as your startup-sequence) can test the RC left by a
program by using the IF command, to enable branching to occur.
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MORE ON FONTS - See PS_FONTS DRAWER for more info
[Thanks to Nick Sullivan for some of this info]
In computerese, "font" refers to a typeface as it appears on screen or in
a printed document, or to the disk file which holds the description of
characters in a typeface.
How do printer fonts, screen fonts, DTP fonts, Postscript fonts, etc
relate to each other?
The Amiga's Fonts
The fonts stored on a Workbench disk (in the Fonts directory) or in memory
(eg, Topaz 8) are just pixel-by-pixel descriptions of each font character,
plus character spacing and other such info. DPaint and Notepad, for
example, are designed to use these fonts and can display them from a menu,
along with the various sizes of each - so "Topaz 8" indicates that the font
is 8 pixels tall from lowest to highest of all letters. Each character has
its own width, ie, these fonts are not "fixed width" fonts.
One drawback is that if you've got Topaz 8, 9 & 11, for example, you can't
get Topaz 14 since the fonts are predefined. WB2, however, does allow for
"font scaling", but the results are blocky to say the least.
Printer Fonts
Printer fonts are those built into the ROM (Read Only Memory) of a
printer, and depending on the quality of the printer can be fairly nunerous
or not. My Epson 500 dot-matrix printer, for example, has Draft, Sans Serif
and Roman, as well as a setting for "slot", ie, for the fonts provided on
an optional card (which I've never bothered to buy). Both the Sans serif
and Roman are NLQ (Near Letter Quality) fonts, meaning the printer simply
uses more dots to create them than the Draft font. All these fonts are
fixed width, which allows word processors to calculate how much text will
fit on each line. It also gives a typewritten look to such printing, rather
than the typeset look. So if your printed text doesn't look like the font
on screen, this is the explanation.
When you get flashier Word processors such as Excellence! or ProWrite,
these enable you to import and use all kinds of "bit-mapped" fonts such as
the Amiga's fonts. But if you want to output these to the printer looking
the same, you'll have to do a "graphic dump", such as ProWrite does in
"normal" print mode. This is slower than sending as simple text, and the
resolution of the printed font can not be better than the resolution of the
original font, thus making it look chunky when printed. If you want
interesting fonts at high resolution, you need to get into using Postscript
fonts.
Postscript Fonts
Postscript is a "page description language" devised by Adobe, and licensed
to certain laser printers and other Postscript output devices. When you
print from a DTP program which is Postscript-compatible (such as Pro Page),
you'll get nice looking output at the maximum resolution of that particular
printer, such as 300 x 300 dots per inch typically for a laser printer, or
up to 2500 x 2500 from a Linotronic typesetter.
So Pro Page and Pagestream both need a Postscript device with Postscript
fonts, as well as corresponding Amiga fonts with "metric files" containing
info about the widths of characters for correct on-screen representation.
Scalable "Outline" Fonts
This is the latest wrinkle in DTP, and uses the same scaling technology
used in Postscript to allow you to get smooth font outlines at any size on
screen. Pro Page uses Compugraphic outline fonts (licensed by Gold Disk)
and another plus is the ability to output the screen to non-Postscript
printers in high quality. The price for this technology is slower screen
updates and printing and more memory requirements.
WB2 has the capability of "bitmap scaling" of Amiga fonts, giving your
Workbench a more professional look.
Downloadable fonts
If you use extra Compugraphic outline fonts in Pro Page, for example, it
is possible to create Postscript downloadable fonts - these are required
when your Postscript printer doesn't have the particular font you need. Pro
Page will automatically download (send) to the printer any such font. This
gives access to many fonts, but requires more memory, time and processing
power.
Check out the Megadisc PD catalogue for many disks full of fonts, both
bit-mapped, and other outline fonts suitable for Pagestream.
Changing Type 1 Fonts to ProDraw Fonts
To use the versatile text capabilities of ProDraw you need to have fonts
in the special clip art format required by ProDraw - which is fine, but
there are few such fonts available. You can use the utility CreateFont
provided on the disk to change Compugraphic fonts to this format, but not,
for example, Type 1 fonts of which there are many available in the public
domain (on our AmigOz disks, for example).
A company called Mirror Image has produced MIoutline to do so however -
it's fully automatic, and will produce the necessary .pdfont file and place
it in the correct directory; it will also produce a "visual index" on your
Postscript printer - ie, showing which letters require which keys to be
pressed.
The problem is: I don't know where this company is, or any other details
of prices, etc. Can anyone help?
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SNAPSHOTTING A RAM DISK ICON
Copy a disk icon to the directory from where you're going to copy it to
Ram, and change your startup-sequence to copy 'disk.info' to Ram. When it
appears as the icon for your Ram disk, snapshot it where you want it to be,
and then copy that snapshotted icon back to where it sits waiting to be
copied each time you boot up - don't forget it's called "Disk.info" so
don't copy it to the root directory of any disk as it will overwrite the
icon for the current disk.
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MEMORY SPEEDS
The Amiga has three types of RAM. Chip-RAM, Fast-RAM and "Slow"-RAM.
Contrary to what many people assert, RAM at $C00000 (the default location
of the A501 expander, and the second 512K of RAM in A2000s) is NOT
fast-RAM, even though the system reports it as such. Because this RAM is
refreshed and accessed via Agnus, it is affected by buss contention in just
the same way as chip-RAM. It is simply a dead area in RAM which is not
accessed by the custom chips and which is not faster than chip-RAM. Moving
this RAM to $80000 (which is what you do to enable 1Mb chip-RAM) will have
no effect on machine speed at all.
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MORE ON 24-BIT COLOUR
[Some info derived from an article by John Lovine]
24 bits is derived by the addtion of 3 8-bit colour components per pixel -
Red, Green and Blue. Each of the 8-bit colour component numbers can
represent one of 256 levels of colour. So when we multiply the possible
combinations of levels of each of the 3 colours we have 256 x 256 x 256 =
16,777,216 (or 2 to the power of 24). So this is why you hear about 16.7
million colours (!!! often with lots of exclamation marks).
Now if you wanted to see all those colours on a screen at one time you'd
need a screen with 16.7 million pixels, or for example, one that was 4096 x
4096 square... Considering that your normal Amiga PAL screen is 640 x 512
= 327680, you can see that 24-bit colour is overkill when it comes to
representing pictures on screen. Indeed if you do a histogram (statistical
picture with the use of image processing software) of a 24-bit pic, you'll
find that there may be 100,000 colours, many of which are a single pixel
only.
The human eye's visual acuity is another factor here - the average eye
needs a colour change of about 1.5% to register a difference; and each
change in level of each 8-bit colour component level is a change of about
.4%, so you need 4 steps of change to be able to perceive a difference,
which would be minimal anyway.
In 18-bit colour we have 6 bits per colour, giving 64 levels each, thus
providing 64 x 64 x 64 = 262144. Each change in level represents a 1.56%
change, thus closely approximating what the human eye can perceive at best.
This suggests that 24-bit colour is indeed overkill, and in fact there are
32- and 48-bit systems currently available on the Mac for people who
seriously overestimate their eyesight. In short, what we need is more
features in the hardware and software but no more "bits" of colour.
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A590 TIMER FIX
If you find that when your A500 & A590 are switched on together you
occasionally get the error message "Not a Dos Disk in Unit 0" or the like,
or the drive takes quite a bit longer to start up, then you probably need
this simple fix: either turn the A590 on several seconds before the
computer, or fit a 3 second timer in the 240 volt supply to the A500 power
supply. This seems to cure the problem.
PRINTER RIBBON REJUNVENATION
Simply spray the ribbon with CRC 2-26 or CRC 5-56, by say, soaking a small
piece of foam rubber and holding it against the ribbon as you rotate it,
either with a pencil or with your battery powered drill.
Thanks to Steve Hack for these two tips.
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