54 lines
5.7 KiB
HTML
54 lines
5.7 KiB
HTML
<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><title>bit-paired keyboard</title><link rel="stylesheet" href="../../jargon.css" type="text/css"/><meta name="generator" content="DocBook XSL Stylesheets V1.61.0"/><link rel="home" href="../index.html" title="The Jargon File"/><link rel="up" href="../B.html" title="B"/><link rel="previous" href="bit-twiddling.html" title="bit twiddling"/><link rel="next" href="bitblt.html" title="bitblt"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">bit-paired keyboard</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bit-twiddling.html">Prev</a> </td><th width="60%" align="center">B</th><td width="20%" align="right"> <a accesskey="n" href="bitblt.html">Next</a></td></tr></table><hr/></div><dt><a id="bit-paired-keyboard"/><dt xmlns="" id="bit-paired-keyboard"><b>bit-paired keyboard</b>: <span xmlns="http://www.w3.org/1999/xhtml" class="grammar">n.,obs.</span></dt></dt><dd><p> (alt.: <span class="firstterm">bit-shift keyboard</span>) A
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non-standard keyboard layout that seems to have originated with the
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Teletype ASR-33 and remained common for several years on early computer
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equipment. The ASR-33 was a mechanical device (see
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<a href="../E/EOU.html"><i class="glossterm">EOU</i></a>), so the only way to generate the character
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codes from keystrokes was by some physical linkage. The design of the
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ASR-33 assigned each character key a basic pattern that could be modified
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by flipping bits if the SHIFT or the CTRL key was pressed. In order to
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avoid making the thing even more of a kluge than it already was, the design
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had to group characters that shared the same basic bit pattern on one
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key.</p><p>Looking at the ASCII chart, we find:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="screen">
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high low bits
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bits 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001
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010 ! " # $ % & ' ( )
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011 0 1 2 3 4 5 6 7 8 9
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</pre></td></tr></table><p>This is why the characters !"#$%&'() appear where they do on a
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Teletype (thankfully, they didn't use shift-0 for space). The Teletype
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Model 33 was actually designed before ASCII existed, and was originally
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intended to use a code that contained these two rows:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="screen">
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low bits
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high 0000 0010 0100 0110 1000 1010 1100 1110
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bits 0001 0011 0101 0111 1001 1011 1101 1111
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10 ) ! bel # $ % wru & * ( " : ? _ , .
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11 0 1 2 3 4 5 6 7 8 9 ' ; / - esc del
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</pre></td></tr></table><p>The result would have been something closer to a normal keyboard.
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But as it happened, Teletype had to use a lot of persuasion just to keep
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ASCII, and the Model 33 keyboard, from looking like this instead:</p><table border="0" bgcolor="#E0E0E0"><tr><td><pre class="screen">
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! " ? $ ' & - ( ) ; : * / , .
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0 1 2 3 4 5 6 7 8 9 + ~ < > × |
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</pre></td></tr></table><p>Teletype's was <span class="emphasis"><em>not</em></span> the weirdest variant of the
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<a href="../Q/QWERTY.html"><i class="glossterm">QWERTY</i></a> layout widely seen, by the way; that prize
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should probably go to one of several (differing) arrangements on IBM's even
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clunkier 026 and 029 card punches.</p><p>When electronic terminals became popular, in the early 1970s, there
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was no agreement in the industry over how the keyboards should be laid out.
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Some vendors opted to emulate the Teletype keyboard, while others used the
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flexibility of electronic circuitry to make their product look like an
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office typewriter. Either choice was supported by the ANSI computer
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keyboard standard, X4.14-1971, which referred to the alternatives as
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“<span class="quote">logical bit pairing</span>” and “<span class="quote">typewriter
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pairing</span>”. These alternatives became known as <span class="firstterm">bit-paired</span> and <span class="firstterm">typewriter-paired</span> keyboards. To a hacker, the
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bit-paired keyboard seemed far more logical — and because most
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hackers in those days had never learned to touch-type, there was little
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pressure from the pioneering users to adapt keyboards to the typewriter
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standard.</p><p>The doom of the bit-paired keyboard was the large-scale introduction
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of the computer terminal into the normal office environment, where
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out-and-out technophobes were expected to use the equipment. The <span class="firstterm">typewriter-paired</span> standard became universal,
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X4.14 was superseded by X4.23-1982, <span class="firstterm">bit-paired</span> hardware was quickly junked or
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relegated to dusty corners, and both terms passed into disuse.</p><p>However, in countries without a long history of touch typing, the
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argument against the bit-paired keyboard layout was weak or nonexistent. As
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a result, the standard Japanese keyboard, used on PCs, Unix boxen
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etc. still has all of the !"#$%&'() characters above the numbers in the
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ASR-33 layout.</p></dd><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bit-twiddling.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="../B.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bitblt.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">bit twiddling </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> bitblt</td></tr></table></div></body></html>
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