Subject:
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Graphics Programming on the Apple II (was: Wow! This guy is good!)
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Newsgroups:
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lugnet.off-topic.geek
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Date:
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Wed, 7 Jun 2000 03:37:49 GMT
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Viewed:
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745 times
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In lugnet.general, Matthew Miller writes:
> Bruce Schlickbernd <corsair@schlickbernd.org> wrote:
> > more acceptable here, but boy, those 16 non-definable colors drove me nuts
> > (let's not mention the Apple ][ and the horrors it imposed). Anyway, I'd
>
> Ohh, lets. No drawing one-pixel wide white lines -- one lone pixel is either
> blue or yellow, depending if it's in an even or odd column. (This is due to
> the techniques Microsoft invented 20 years later for their ClearType
> technology...)
Mein Gott! Someone who actually remembers graphics programming on the Apple II!
But I remember things a little differently.
A pixel was defined in a rather slippery fashion in Apple II "high-resolution"
graphics. A pixel was either one bit or two, depending on the values of
adjacent bits. The four basic colors were blue, violet, green, and orange (no
yellow!). You could only get white by having two adjacent bits turned on. Two
adjacent bits turned off = black.
Why was it done this way? It had nothing to do with Microsoft. Several years
ago I heard an interview with one of the original employees of Apple (not Jobs
or Wozniak) on a local public radio station. He was discussing the quirky Apple
II graphics. He said that the reason that the graphics were implemented the way
they were had to do with saving money -- but not actually very much! Jobs and
Wozniak set out to make the Apple II for under $1,000, out-of-pocket. The logic
required to give each pixel two independent bits would have cost them -- get
ready -- an extra six dollars.
Probably more significant, at two bits per pixel, a page of high-res graphics
would have occupied twice the memory space. The high-res page, as implemented,
occupied 16K of RAM. If high-res graphics were implemented in a way that
required 32K of RAM, two things would have happened: 1) at a time when RAM was
really, really expensive, no one would ever use high-res graphics; 2) the 6502
could only address 64K of RAM, and the "page-flipping" approach to displaying
flicker-free high-res graphics would have required all the addressable memory
space of the CPU. Oops.
In 1982, I got my Apple II. The only reason that I got 64K of RAM for it was
that my Dad worked at National Semiconductor, and was able to obtain "cosmetic
reject" 16K RAM chips from the factory floor. They looked ugly, but they
worked.
It's all *so* much easier now -- you just have to understand the Windows API!
:^P
--
John J. Ladasky Jr., Ph.D.
Department of Structural Biology
Stanford University Medical Center
Stanford, CA 94305
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Message has 2 Replies:
Message is in Reply To:
 | | Re: Wow! This guy is good!
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| (...) Ohh, lets. No drawing one-pixel wide white lines -- one lone pixel is either blue or yellow, depending if it's in an even or odd column. (This is due to the techniques Microsoft invented 20 years later for their ClearType technology...) (24 years ago, 7-Jun-00, to lugnet.general, lugnet.off-topic.geek)
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