Could someone enlighten me as to what exactly this means?
ASCII technically only defines 128 characters, represented by the binary numbers 0-127. Since it only takes seven bits (2[sup]7[/sup] = 128) to make those numbers, all ASCII characters are in the form 0xxxxxxx. Where each x is either 0 or 1. The more left a digit is in that number, the more significant it is, so that zero is the most significant bit (or high order bit). The last x is the least significant bit. So if they’re talking about the seven least significant bits in an eight bit byte, they’re talking about everything to the right of that first 0.
Thanks, friedo. I was under the impression that ASCII defined 256 characters. Was the original ASCII character set only 7 bits, with the eighth added when they realized seven wouldn’t be enough? Why would you make a character set that wasted a bit like that, considering that modern bytes are 8 bits and you’d have to have that leading zero in there anyway?
Nope, the ascii standard was 7 bits and, in fact the internet was all 7 bits and many parts of it remain 7 bits and 8 bit data needs to be encoded. Anyone remember UUENCODE? Ah, memories.
Well, what’s the logic behind the wasted bit, then? Or am I incorrect in assuming a bit would be wasted?
I have a computer textbook that claims the ASCII and EBCDIC character sets have 256 characters each. Of course, this isn’t an authorative source. I’ve found errors in it before. (Nothing pisses me off more than paying $60 for a paperback, ring-bound book and finding errors!) This may well be another one.
So why are there 256 characters in the Windows character map. Is the 8th bit an unofficial extension to the ASCII character set?
The 8th bit was often used as a parity bit (even for use in memory). Eventually the use of the 8th bit for parity was dropped, and now most systems take advantage of the 8th bit to give 256 different characters. There isn’t a lot of standardization about what the upper 128 codes are supposed to represent, though. The Windows character map above 128 is just one of many possibilities. Technically, ASCII refers to just the lower 128 (0-127, as friedo said). Note that this is only tangentially related to whether a byte is 8 bits or not 
Arjuna34
Arjuna34
Ah, that makes sense. Thanks, Arjuna. I realize that it’s not directly related to the OP, but it didn’t really seem worthy of another thread, and hey, what can I say? I was curious.
While I’m posting, I might as well jump into the fray on the 8-bit byte controversy
At one time (i.e. 60’s, and somewhat into the 70’s) someone might mean a 9-bit quantity with the word “byte”, as in the examples friedo found (notably the 36-bit word computers, and the venerable PDP-10/11). Friedo and sailor are both right in one sense or another- it boils down to what you mean by “define”.
I’d side with sailor on this, though. You would almost never hear someone use the word “byte” to mean anything other than 8 information bits. If one were talking about a 6-bit quantity in a 36-bit computer, a hardware or firmware EE (of which I’m one) would use the all-purpose term “word”, which can mean number of bits, depending on the context. The only way I could imagine using “byte” to mean 6 bits in this example would be if we were heavily into debugging or fixing a 36-bit system, and constantly refering to the 1960’s or 70’s era documentation, which might use the word “byte” frequently. I could see a tendancy to lapse into the documenation’s terminology for a while. This is somewhat of a stretch though, and would just be applicable in this situation. If I talked to the same colleague later in the day about another, modern system, and used the word “byte”, he wouldn’t expect it to mean anything else than “8 bits”.
I wouldn’t rely too heavily on the argument that “byte == character”, either. Historically, one byte could hold one printable character, but as others have pointed out, ASCII is only 7 bits, and now with unicode, etc., one character can be 16 bits. One byte per character was just convenience, not an equality. The jargon file is fun, but not always accurate. It contradicts itself in the definition of a byte when it says that 1 byte = memory for 1 character, then mentions the 1-36 bit “bytes” of the PDP-10. Could the PDP-10 encode a character in 1 bit???
Also, I’ve worked with 4-bit microprocessors, some of which could only address 4 bits at time. Not many people would call a “byte” 4 bits, even though it was the minimum addressable unit of memory storage. I’ve also programmed several 8-bit microcontrollers that had bit-addressable memory- in that case 1 bit was the minimum addressable storage (each bit had a separate memory address), but I don’t think too many people will argue that “1 bit = 1 byte”.
Anyway, “byte” has meant several things in the past, but now it’s pretty much 8 information bits. I guess I should check for an IEEE, ISO, or ANSI standard defining it to be sure though
Arjuna34
ASCII was/is 7 bits. Then IBM and other manufacturers each came out with several 8 bit “extended” ASCII. If you look at the headers of emails and HTML pages you will see, for example (in email):
Content-Type: text/plain; charset=“iso-8859-1”
Content-Transfer-Encoding: 8bit
Out of curiosity, I checked an ordinary dictionary, the American Heritage:
byte n. 1. A sequence of adjacent bits operated on as a unit by a computer. 2. The amount of computer memory needed to store one character of a specified size, usually 8 bits for a microcomputer and 16 bits for a larger computer.
That definition appears in the list at dictionary.com, as does the entries in the jargon file, and others. I’m pretty sure there are some PDP-10s still floating around, though they are “obsolete.”
manhattan, self-deprecating humor is allowed in GQ.
Yeah, I think we have sufficient evidence and Friedo pretty much has his own mind. Not to hammer this point further but I found some quotes about MPI, iso-8859, ISO 9660 and ISO 11544 defining a byte as 8 bits (but I did not look for them so who knows what the context may be?). Also that the French translation for byte is “octet” and the Spanish “octeto” but the agreed abbreviation is still B because “o” would be easily mistaken for the number zero. It is safe to say that even in France octets would have 8 bits.
But, of course, there is no Universal Authority (God was unavailable) so I can find 1000 standards that agree with me and you can still find some obscure document that doesn’t. You can pretty much find support for anything on the Net, even if it is plain wrong. If you cannot find support for your theory you are really alone.
From another email header:
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
sailor: You make the mistake of assuming that the most common definition is the ONLY definition. A byte certainly CAN be more or less than 8 bits. If I were to develop a 36 bit computer right now, I would be more than justified in calling a 6 bit section a byte. Bytes can be (as evidenced by the jargon file entry, which, as any hacker knows, is the ONLY definition that matters) any size, it’s just that CURRENTLY, damned near every computer uses 8 bit bytes. That doesn’t mean that bytes are only 8 bits.
To use a computer related example, you saying that a byte is ALWAYS 8 bits is like saying a floppy disk is ALWAYS 3.5". Certainly, today that is nearly always the case. But that doesn’t mean floppy disk is defined as being 3.5". It could also be 5.25" or 8". They exist, and just because they are obsolete, it does not make the definition of a floppy as ALWAYS 3.5" any more accurate.
quote:
An amount of memory or data smaller than a word; usually eight bits; enough to represent one character; the smallest addressable unit of storage.
The above, posted previously, is the best definition of byte I have seen in this thread. The important part being “the smallest addressable unit of storage”.
I used Honeywell machines with 6 bit bytes in 1973 well after the “IBM guy” supposedly “standardised” things in 1956. I have also worked on computers with 38-bit words.
Bytes generally have 8 bits these days, but it is wrong to say that a byte is “defined” as 8 bits.
Well, we are beating a dead horse here. I have already asked for any instances in which it is used like that or any proffesional who would use it like that and we cannot find any.
I think it is safe to say that the definitions of words would derive from their common usage. That is the way dictionaries are made, they find instances of the word and interpret the meaning. When a meaning is common, then it is included in the definition. A single or very few instances would not be enough and you cannot supply a single one.
I have searched the net and cannot find a single one! I think I am safe in saying the only common use of byte today is to mean 8 bits. You disagree but you cannot find any support for your assertion. Well, what can I say? Ok, whatever.
But, as I also said, there is no absolute authority to settle this so if one person (Friedo) says, “to me it can mean anything” then we’ll have to accept it. For him that is the definition. But I have yet to see any authority in that field use the word as he says.
The fact remains that if you want people to understand you and not confuse things, you better stick with the 8 bit definition or else give a lengthy explanation beforehand.
Dave Barry wrote an article where he used the word “Oregonian” to mean “penis”. Does that mean “Oregonian” now means penis? i think it would take more than a few cites to have that meaning accepted but if you want to argue Oregonian means penis, be my guest.
I have an acquaintance who is a lawyer and a pedant and he likes to go into these obscure semantic disquisitions. He might be technically right but the fact is people start rolling their eyes and it ruins the conversation.
His last item was the word “port” and he insisted it meant “door” and kept going and going and going and going… he totally sidetracked the conversation on this issue and even when people were looking at each other and rolling their eyes the guy kept going.
Well, let’s assume he was technically right and the word port means door (as the door to a computer or to a country). I don’t care!! We are trying to communicate and anybody with a few brain cells can understand that even if technically or in an obsolete usage “port” meant “door” when people speak everyday English “port” does not mean door and the object of the conversation is not to determine how much he may know about the word.
In the end, after a lot of eye rolling, everybody concedes port can mean anything you want it to and they go home knowing who they should avod in the future.
So, Ok, despite the fact that among people who work with software and hardware the word “byte” universally means 8 bits, and despite the fact that you cannot produce a single instance that contradicts this, I will concede it is not illegal or immoral to use the word “byte” to mean something else (even if it may be confusing) and, in fact, it may have been used like that many years ago. I agree to this of my own free will and not subject to any coercion.
Where do I have to sign?
<sigh>
Besides, we all know port really means left.
Perhaps I should mention, I work with software on a semi-pro level (ie, still in school, but have done work on the side.)
There are actually a number of different things you can mean when you say “ASCII”, so it’s a little hard to argue about whether it’s 7-bit or 8-bit. One of the most common explicitly standardised ASCII versions is NVT-ASCII (Network Virtual Terminal) which is used in all text-based network protocols (e.g. FTP, HTTP, SMTP, POP, Telnet, …),and is 7-bit (i.e. 128 characters). You can read about it in RFC 854 (the Telnet Protocol). There’s an amusing little section in there about non-8-bit-byte machines (anybody used MULTICS recently? :))
>> Besides, we all know port really means left.
Well, it depends on your point of view and other variables… In reality it means larboard unless you are in France where it means babord.
Since this thread has degenerated into total silliness and playing with words, I thought I’d contribute the following which I first heard as a kid and makes as much sense to me as any of the previous posts:
Why is a fire engine red?"
A fire engine’s red.
A newspaper’s read too.
Two and two are four.
Three times four is twelve.
Twelve is a ruler.
Queen Mary is a ruler.
Queen Mary is a ship.
The ship sails the sea.
The sea has fish.
The fish have fins.
The Finns fought the Russians.
A fire engine’s always a-rushin’.
A Russian is red.
That’s why a fire engine’s red.
So, why is a byte 8 bits?
Why does a byte have eight bits?
A byte has eight bits
A dollar has eight bits too
Two dollars pay your taxes
Texas is a State
Maryland is a state
Mary had a little lamb
Lamb makes good kebob
Bob can’t get it up
Up is the opposite of down
Down is from a duck
A duck is a quack
A quack will take your dollars
Dallas is a city
In the city you can get a snack
A snack is a bite
That’s why a byte has eight bits.
Now I’d like to see you rebutt that argument.
Nope, that’s to convert an 8bit file to 7bit (minus certain non-printing characters).
Used to post binaries in text context, like for Usenet porn. 