Why 8 Bits = 1 Byte? LED Display & Parity Bit

[frenzal_dude]

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?

 

[DaveC426913]

I know that one character is one byte,

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

and that is 7 bits + 1 parity bit.

No. Only in applications where they decide they they need a parity bit.

Is it made up of 7 bits because on an LED display the figure 8 is made up of 7 segments?

No.

 

[rbj]

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

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.

 

[dlgoff]

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

You are showing your age you know?

 

[turbo]

You are showing your age you know?

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.

 

[dlgoff]

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.

Another old man. :grumpy:

Edit: BTW Grumpy comes with the territory. Just sayin'.

 

[DaveC426913]

[geezer voice]6 bits. Hmph. Why, I remember when bytes were 2 bits.[/geezer voice]

 

[rbj]

You are showing your age you know?

okay, so how old am i?

:-)

 

[rbj]

[geezer voice]6 bits. Hmph. Why, I remember when bytes were 2 bits.[/geezer voice]

?

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.)

 

[dlgoff]

okay, so how old am i?

:-)

Not old enough evidently.

 

[turbo]

[geezer voice]6 bits. Hmph. Why, I remember when bytes were 2 bits.[/geezer voice]

And you had to walk uphill to school and back home every-day all winter...

 

[turbo]

Uphill both ways!

 

[sophiecentaur]

?

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.)

That's how I remember it, too. I also remember the 39bit word - for two 18bit instructions with a B line modifier bit.

 

[256bits]

Haha - i can't remember what i had for breakfast yesterday - was it 2 nibbles of toast or a byte.

 

[mathman]

[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.

 

[wuliheron]

I always assumed it was because of the rhyme, you know:

Two bits, four bits, six bits, a dollar...

 

[rcgldr]

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, ...)

 

[jtbell]

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