Re: questions about bits and bytes
At 12:00 AM 4/10/96 -0700, Bill Stewart wrote:
At 09:33 PM 4/8/96 -0400, Jack Mott wrote:
This may be a bit of a no brainer, but everything I have read sorta skips over this point. a bit is 1 or 0. 8 bits make up a byte (0-255).
Be careful writing code - sometimes a byte is -128 to 127 instead of 0 to 255. Also, there are machines (mostly old kinky ones) that use bytes of sizes other than 8 bits.
No, Bill, a "byte" has ALWAYS been 8-bits. One of the main reasons the term "byte" was invented was because the term "word" (as in, "word length") varied for different computers, especially in the 1960's. (In fact, many computers of that era used word lengths other than 8, 16, 32, 64 bits, as surprising as this may sound to the current crop of PC and Mac afficionados.) This made it inconvenient to talk about memory capacities unless you were referring to the same machine. The solution was to invent a new term, "byte," which conviently had about the same size as an ASCII character and was always 8 bits.
jim bell <jimbell@pacifier.com> writes:
Be careful writing code - sometimes a byte is -128 to 127 instead of 0 to 25 Also, there are machines (mostly old kinky ones) that use bytes of sizes other than 8 bits.
No, Bill, a "byte" has ALWAYS been 8-bits. One of the main reasons the term "byte" was invented was because the term "word" (as in, "word length") varied for different computers, especially in the 1960's. (In fact, many computers of that era used word lengths other than 8, 16, 32, 64 bits, as surprising as this may sound to the current crop of PC and Mac afficionados.) This made it inconvenient to talk about memory capacities unless you were referring to the same machine. The solution was to invent a new term, "byte," which conviently had about the same size as an ASCII character and was always 8 bits.
I used to hack a CDC Cyber box designed by Seymour Cray before he started his oen company. It had the following curious features: 1 word = 10 _bytes_ = 60 bits 1 _byte_ = 6 bits Out of respect for Jim, I dug up the dox, which say: "On the 6600, the basic bit groupings are 6, 12, 15 and 30 bits". The dox consistently refer to the 6-bit chunks as "characters", never bytes. However I've heard people refer to 6 bits as bytes and to 3 bits (an octal digit) as nybbles. Naturally, the character set had only 64 symbols - no lowercase letters. Both integers and reals were 60 bits. Addresses in the instructions were 15 bits, but that was an address of a 60-bit word. Negative numbers were represented with one's compliment (i.e. -X = NOT X). Hence there were two zeroes: positive and negative. I believe BESM-6 also had 6-bit bytes. I have the dox for it someplace (in Russian) but can't find them offhand. Moral: it's not necessarily redundant to say '8-bit byte'. --- Dr. Dimitri Vulis Brighton Beach Boardwalk BBS, Forest Hills, N.Y.: +1-718-261-2013, 14.4Kbps
Dr. Dimitri Vulis writes:
I used to hack a CDC Cyber box designed by Seymour Cray before he started his oen company. It had the following curious features:
1 word = 10 _bytes_ = 60 bits 1 _byte_ = 6 bits
. . .
I believe BESM-6 also had 6-bit bytes. I have the dox for it someplace (in Russian) but can't find them offhand.
Moral: it's not necessarily redundant to say '8-bit byte'.
Which is precisely the reason the IETF always refers to "bytes" as "octets". "Octet" is defined to be eight bits, regardless of local word sizes.
No, bytes are no always 8 bits - some machines use(d) 9-bit bytes. That's why we have the word octet. --- They say in online country So which side are you on boys There is no middle way Which side are you on You'll either be a Usenet man Which side are you on boys Or a thug for the CDA Which side are you on? National Union of Computer Operatives; Hackers, local 37 APL-CPIO
Simon Spero writes:
No, bytes are no always 8 bits - some machines use(d) 9-bit bytes. That's why we have the word octet.
Indeed, machines have come in all flavors of byte size. Byte size on PDP-6 descended machines, including the PDP-10 and DECSystem-20, was always variable -- byte pointers could extract any length from one bit to 36 bits, and byte size was an attribute of files under several operating systems that ran on that series. I remember that many of the MIT crowd favored 9 bit Extended ASCII, using the so called space-cadet keyboards that set the two high bits when control and meta were hit, and with the area we think of as the control characters being taken up by other symbols. "Byte" only came to mean "Eight Bits" consistantly in the last decade or less. "Octet" is the only really consistant term. Perry
On Wed, 10 Apr 1996, jim bell wrote:
Be careful writing code - sometimes a byte is -128 to 127 instead of 0 to 255. Also, there are machines (mostly old kinky ones) that use bytes of sizes other than 8 bits.
No, Bill, a "byte" has ALWAYS been 8-bits.
Not that it really matters, but you're wrong; if you're talking about an asynchronous data stream, a byte is however many bits it takes to express one character. If you're using ASCII, it's 8; if you're using Baudot, it's 5. If you're talking about data in computers, then I think you're right, a byte is always 8 bits. -rich
jim bell writes: : >At 09:33 PM 4/8/96 -0400, Jack Mott wrote: : . . . . : >Also, there are machines (mostly old kinky ones) that use bytes of sizes : >other than 8 bits. : : No, Bill, a "byte" has ALWAYS been 8-bits. One of the main reasons : the term "byte" was invented was because the term "word" (as in, "word : length") varied for different computers, especially in the 1960's. (In fact, : many computers of that era used word lengths other than 8, 16, 32, 64 bits, : as surprising as this may sound to the current crop of PC and Mac : afficionados.) This made it inconvenient to talk about memory capacities : unless you were referring to the same machine. The solution was to invent a : new term, "byte," which conviently had about the same size as an ASCII : character and was always 8 bits. One trouble with this statement was that an ASCII character only has 7 bits. Another is that when I snuck into the IBM Executive Computer Concepts Course in the mid-sixties, we [a bunch of high-powered executives and me] were told, as I recall, that originally the term byte was used by some to represent 7 bits. IBM took credit for standardizing the term on 8 bits. -- Peter D. Junger--Case Western Reserve University Law School--Cleveland, OH Internet: junger@pdj2-ra.f-remote.cwru.edu junger@samsara.law.cwru.edu
participants (7)
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dlv＠bwalk.dm.com -
jim bell -
Perry E. Metzger -
Peter D. Junger -
Rich Graves -
Scott Brickner -
Simon Spero