Subject:
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Re: Mechanical Memory for Computing
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 26 Jun 2003 16:07:24 GMT
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Original-From:
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Bruce Boyes <bboyes@systronix.com&spamcake&>
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Viewed:
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626 times
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Quoting Ross Crawford <rcrawford@csi.com>:
> Actually a byte is whatever you define it to be - a nibble is generally
> half a byte, and a word is generally 2 bytes.
Not to start a tempest in a teapot but I know of no recent computer language
or hardware which defines a byte as anything other than 8 bits. "byte-wide"
I/O is always 8 bits wide as are byte-wide registers. Were it not so, there
would be extreme confusion in hardware and software.
In the C world there can be disagreement on different hardware platforms
about the number of bits in an int (16 or 32), word or long word, but the
size of a byte is always 8 bits. Intel vs Motorola hardware differs in where
bit0 is, which drives programmers and designers crazy.
A nibble being half a byte can therefore hold one hex digit 0x0-0xF and a
byte can hold two - 0x00 through 0xff.
On advantage of Java is that all primitive sizes - byte, int, long, etc are
all the same on all hardware, making such definitions truly standardized in
a way which they never were with C tools. The 'endian-ness' of data is also
standardized across all platforms so there is no confusion about whether
'bit 0' is the least- or most- significant bit and where it's located. In
Java it's always the rightmost bit and always the least significant.
Bruce
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Message has 2 Replies:
 | | Re: Mechanical Memory for Computing
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| (...) Various network protocols define bytes as 7-bit + parity. Almost all modern modems still support this, for a simple example. Historically, the hardware-defined 'most covenient' integer size was called the 'word', with word sizes ranging from 4 (...) (21 years ago, 26-Jun-03, to lugnet.robotics)
| | | Re: Mechanical Memory for Computing
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| (...) Depends on what you call 'recent' :-) The DEC PDP-8 had 12-bit words with 6-bit bytes, if I recall correctly. There were also computers with 36-bit words containing six 6-bit bytes in one word (DEC 10/20?), or three 12-bit bytes. The DataSaab (...) (21 years ago, 30-Jun-03, to lugnet.robotics)
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