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Why 8 bits = 1 Byte?

  1. Dec 10, 2011 #1
    I know that one character is one byte, and that is 7 bits + 1 parity bit.

    Is it made up of 7 bits because on an LED display the figure 8 is made up of 7 segments?
     
  2. jcsd
  3. Dec 10, 2011 #2

    DaveC426913

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    One character is one byte because, when they decided, they figured 256 (2^8) characters was all they'd need.

    http://en.wikipedia.org/wiki/Byte
    No. Only in applications where they decide they they need a parity bit.


    No.
     
  4. Dec 10, 2011 #3

    rbj

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    actually, i think they originally thought they only needed 128 characters. that's what the original ASCII code is. before that there were 6-bit codes that had fewer characters.

    i think that when they realized they needed more than 64 chars (6 bits) to get all of the lower case, upper case, numerals, punctuation, and control characters they needed, they figured why not go to 8 (a handy power of two) and sometimes they used that 8th bit for parity and sometimes they used it for an extension to the ASCII standard. and sometimes they just set the 8th bit to zero.
     
    Last edited: Dec 10, 2011
  5. Dec 10, 2011 #4

    dlgoff

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    You are showing your age you know? :biggrin:
     
  6. Dec 10, 2011 #5

    turbo

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    You are actually showing your age by jumping in and helping out on this one. I tend to try to stay out of these, if I can.
     
  7. Dec 10, 2011 #6

    dlgoff

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    Another old man. :grumpy:

    Edit: BTW Grumpy comes with the territory. Just sayin'.
     
    Last edited: Dec 10, 2011
  8. Dec 10, 2011 #7

    DaveC426913

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    [geezer voice]6 bits. Hmph. Why, I remember when bytes were 2 bits.[/geezer voice]
     
  9. Dec 10, 2011 #8

    rbj

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    okay, so how old am i?

    :-)
     
  10. Dec 10, 2011 #9

    rbj

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    ????

    i thought it was 2 nibbles per byte, not the other way around??

    so, Dave, who can out geezer the other?


    (i remember when either JFK bought it.)
     
  11. Dec 10, 2011 #10

    dlgoff

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    Not old enough evidently. :rolleyes:
     
  12. Dec 10, 2011 #11

    turbo

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    And you had to walk uphill to school and back home every-day all winter...
     
  13. Dec 11, 2011 #12

    turbo

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    Uphill both ways!!
     
  14. Dec 11, 2011 #13

    sophiecentaur

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    That's how I remember it, too. I also remember the 39bit word - for two 18bit instructions with a B line modifier bit.
     
  15. Dec 12, 2011 #14
    Haha - i can't remember what i had for breakfast yesterday - was it 2 nibbles of toast or a byte.
     
  16. Dec 12, 2011 #15

    mathman

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    [Showing my age] . When IBM first introduced the 360 series of computers, it decreed that a byte should be 8 bits. Before then it had been 6 bits.
     
  17. Dec 12, 2011 #16
    I always assumed it was because of the rhyme, you know:

    Two bits, four bits, six bits, a dollar....
     
  18. Dec 12, 2011 #17

    rcgldr

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    There's alway's wiki (plus I'm an old guy that remembers some of this):

    baudot which eventually evolved into ITA2 / USTTY - 5 bit code:

    http://en.wikipedia.org/wiki/Baudot_code

    CDC display code - 6 bit code, actually stored as 6 bit characters in 24 bit, 48 bit, and 60 bit words on CDC computers:

    http://en.wikipedia.org/wiki/CDC_display_code

    IBM 1400 BCD - 6 bit code (but stored in 8 bit bytes):

    http://en.wikipedia.org/wiki/IBM_1401

    ASCII - originally 7 bit code:

    http://en.wikipedia.org/wiki/ASCII

    EBCDIC - 8 bit code:

    wiki EBCDIC.html

    UTF-8 - 8 bit code, UTF-16 - 16 bit code:

    http://en.wikipedia.org/wiki/Unicode

    Trivia - CDC 6600 / 7600 had 60 bit words (+ 4 bits of parity). CDC 3000 series had 24 bit and 48 bit word size. CDC Star had true 64 bit words. IBM 360 -> 390 had 32 bit words. Most of the old mini-computers had 16 bit word size (Computer Automation, Data General Nova, HP 2100 series, IBM 1130, Micro Systems, Varian Data Machines, ...)
     
    Last edited: Dec 12, 2011
  19. Dec 12, 2011 #18

    jtbell

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    Staff: Mentor

    The Digital Equipment PDP-10 had 36-bit words.
     
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