4 ms·

Did anyone notice how in the code listings, the O's had slashes through them to distinguish them from zeroes, instead of the other way around? I wonder when it

Did anyone notice how in the code listings, the O's had slashes through them to distinguish them from zeroes, instead of the other way around? I wonder when it became a standard to slash the zero.

phendrenad2 6y ago
That seems like it must be a mistake. How could things have flipped 180 degrees like that? I'll need to investigate other programming books from this era... EDIT: I do appreciate the Game of Thrones look it gives some of the pages. Especially the error messages like "T00 MANY L00PS"
- kesslern 6y ago
  Seems to be an artifact of the teletype system. From the bottom of page 4: > The third observation is that we only use capital letters, and that the letter "Oh" is distinguished from the numeral "Zero" by having a diagonal slash through the "Oh". This feature is made necessary by the fact that in a computer program it is not always possible to tell from the context whether the letter or number was intended unless they have different appearance. The distinction is made automatically by the teletype machine, which also has a special key for the number "One" to distinguish it from the letter "Eye" or lower case "L".
  - dboreham 6y ago
    This implies they were using the same character code for O,0 and l,1. Definitely not ASCII so perhaps some 5-channel code? IBM 716?
    - Someone 6y ago
      That was common on early typewriters. Examples: https://en.wikipedia.org/wiki/Sholes_and_Glidden_typewriter#/media/File%3ASholes-Glidden_1874.jpg https://en.wikipedia.org/wiki/Sholes_and_Glidden_typewriter#... https://www.reddit.com/r/typewriters/comments/2b4y0d/why_is_there_no_1_or_0_on_my_underwood_typewriter/ https://www.reddit.com/r/typewriters/comments/2b4y0d/why_is_...
- fuzzfactor 6y ago
  >How could things have flipped 180 degrees like that? Somebody other than IBM came along? IIRC electronic communication started with just ones & zeros then later got the rest of the numerals. Eventually they got (upper case only) alphabetic characters and by that time a plain zero had already been well established. Teletypes made sure the letter O always appeared different than the numeral zero. I never actually used Teletypes until the 1980s where we still got official cables by Telex. But even then a large number of experienced administrators had learned to type manually on traditional typewriter keyboards which are also hard to press but there was no zero or 1 key when they learned. It was important not to reflexively substitute letters for numbers, and if you did you needed to be able to tell the difference on paper. The ones they are talking about are some of the earliest ASCII Teletypes, where the numerals were wisely standardized equal to the least significant 4 bits out of their total of 7 bits. Zero is 0000, and upper case O coincidentally is 1111. IBM had its own standard before ASCII, apparently IBM printers produced a slashed upper case O before that. At Dartmouth it looks like the Teletype Model 35's they had were combining or overprinting the regular slash and zero fonts to make upper case O IBM style, and it appears their keyboards reflected the slashed output. The actual printouts show this. The main part of the documentation looks like the typical output of a manual electric IBM typewriter instead, where they slashed the O by backspacing. Looks even more funky compared to the real printout. Any typos would have been corrected the modern way, painting over them with Liquid Paper then retyping after it dried. The original printouts didn't always need to be actually cut with scissors & pasted into the document like lots of ordinary graphics since sometimes it was a whole page, they just manually typed a page number at the bottom and it got Xeroxed into its place. Others were probably cut with a paper cutter beforehand, not scissors. ASCII had early revisions about this time, within a few years I was a youngster in an office where we got one of the first "luggable" printing terminals and connected to a mainframe through a telephone modem over long-distance AT&T lines. With the suitcase model and acoustic coupler modems we could log in to the "host" with our "laptop" from clients' offices or residences to serve them with more computing power than anyone else around. These were some of the first that were made for computer use not for the Teletype network. Just an early RS-232 connector with 6-conductor cable to the DB-25 socket on the modem. RS-232B at first then RS-232C, still waiting for RS-232D, expected after they landed on the moon. They weren't quick enough and IBM put RS-232C on the desktop, called it a "COM" port and its been that way ever since. Well if you still want to have the remaining possibility of doing fully-backward-compatible serial communication, and without needing hardware-specific drivers to communicate with any vintage of computer or modem. This was the first time I saw the slashed zero, never the slashed upper case O. And it was a traditional non-typewheel mechanism, electically powered so the keyboard was not mechanical, but otherwise it made as much noise as a really fast hard-hitting typewriter, making multiple copies on modern carbonless triplicate rolls. People were amazed with new technology back then. Eventually with PC's a number of office people connected external modems to their standard COM ports to log into servers, usually plugged right into a modular Bell system phone jack rather than acoustically coupled to the standard telephone handset, plus autodialing became available. Their standard serial mouse was on their other COM port. If they had DOS software that supported a mouse, which was not yet common. As a web began to appear these were the only people already equipped to partake, but in the long run the net got popular and built-in modems were common expansion cards (later standard equipment way before RJ45 ethernet) which connect right to the phone jack without needing a physical COM port. Plus the next modems were built into the motherboards which all just had phone jacks for a while, mostly software modems.
alexjm 6y ago
I think I've seen some older content where the convention was reversed like this. Wikipedia's article on slashed zero claims that IBM and some other mainframes put their slash on the letter O instead of the number 0. However, in a bit of circularity, its citation (1) is this same BASIC manual. Checking an IBM manual (2) for punching cards, neither 0 nor O has a slash. The manual is undated, but documents the model 26 keypunch from 1949 and not the model 29 keypunch from 1964, so it's probably older than this BASIC manual. 1: https://en.wikipedia.org/wiki/Slashed_zero#cite_ref-9 https://en.wikipedia.org/wiki/Slashed_zero#cite_ref-9 2: https://archive.org/details/bitsavers_ibmpunchedAnIntroductiontoIBMPunchedCardDataProces_2436138/page/n5/mode/2up https://archive.org/details/bitsavers_ibmpunchedAnIntroducti... (page 4, 15)
- Someone 6y ago
  On IBM punched cards, the letters needn’t look very different, as you could always look at the punches (digits have only one punch; also look at the patterns for letters A-I, J-R, and S-Z) And yes, people learned that. Because the primary output of a puncher were the holes, not the printed text, maintenance of the ‘print’ part wasn’t always done well (ink smear or devices that ran out of ink), resulting in print output didn’t look remotely as clean as that manual shows.
8bitsrule 6y ago
That's a tough question. The slash-0 (for decimal zero) had been in use long before the BASIC and the ASR-33 came along. (In ham radio for one.) Dartmouth or Teletype may have had a reason for trying this ... but it didn't last! [Edit] OK, think I found the culprit. "The rule which has the letter O with a slash and the zero without was used at IBM and a few other early mainframe makers; this is even more of a problem for Scandinavians, because it looks like two of their letters at the same time." -- https://simple.wikipedia.org/wiki/Zero#Telling_zero_and_the_letter_O_apart https://simple.wikipedia.org/wiki/Zero#Telling_zero_and_the_...
dmolony 6y ago
I remember in 1976 we were using mark sense cards to write programs, and we definitely had to slash the letter O. I think we also had to slash the Z to distinguish it from a 7.
- HarryHirsch 6y ago
  I think the purpose of the Z-slash was to distinguish from the digit 2.
lsllc 6y ago
At least as early as 1977 the Commodore PET and the Apple ][ had "slashed zeros"; followed by the Atari 400/800 in 1979, the BBC Micro in 1981 and the Sinclair ZX Spectrum and Commodore 64 in 1982: https://damieng.com/blog/2011/02/20/typography-in-8-bits-system-fonts https://damieng.com/blog/2011/02/20/typography-in-8-bits-sys... Uh, ok. Turns out it was the 12th and 13th century that it was first known to have been used! https://en.wikipedia.org/wiki/Slashed_zero#Origins https://en.wikipedia.org/wiki/Slashed_zero#Origins
todd8 6y ago
In the 60's there was no consistent standard for this. I remember this being written about in the CACM 1967. Those with access to old copies of the Communications of the ACM can take a look at [1]. Here is the title and abstract: Towards standards for handwritten zero and oh: much ado about nothing (and a letter), or a partial dossier on distinguishing between handwritten zero and oh, by R.W. Bemer The Chairman of the ACM Standards Committee, Julien Green, has charged me with making “more effective use of CACM for communication … to get grass-roots opinions from the ACM membership.” This paper is the first attempt. A partial dossier on distinguishing between handwritten zero and the letter oh is assembled here. This presentation was triggered by a request for guidance in this matter presented by the United Kingdom Delegation to ISO/TC97/SC2, Character Sets and Coding, at the meeting in Paris on 1967 March 13-16. The matter is just now in the province of USASI X3.6, to which comments might be directed. Comments will be expected within sixty days [by approximately October 1st]. [1] https://dl.acm.org/doi/10.1145/363534.363563 https://dl.acm.org/doi/10.1145/363534.363563
todd8 6y ago
Many years ago I adopted the personal convention of using a slash for the number zero and a little curly cue at the top of the capital letter O. By using both in my handwriting where they could be confused, I was free to use just an unadorned letter or digit in situations where context made it clear. [1] Like the capital O found in the google font: https://fonts.google.com/specimen/Cedarville+Cursive?category=Handwriting&preview.text=big%20O&preview.text_type=custom https://fonts.google.com/specimen/Cedarville+Cursive?categor...

Did anyone notice how in the code listings, the O's had slashes through them to distinguish them from zeroes, instead of the other way around? I wonder when it became a standard to slash the zero.

phendrenad2 6y ago

That seems like it must be a mistake. How could things have flipped 180 degrees like that? I'll need to investigate other programming books from this era... EDIT: I do appreciate the Game of Thrones look it gives some of the pages. Especially the error messages like "T00 MANY L00PS"

kesslern 6y ago
Seems to be an artifact of the teletype system. From the bottom of page 4: > The third observation is that we only use capital letters, and that the letter "Oh" is distinguished from the numeral "Zero" by having a diagonal slash through the "Oh". This feature is made necessary by the fact that in a computer program it is not always possible to tell from the context whether the letter or number was intended unless they have different appearance. The distinction is made automatically by the teletype machine, which also has a special key for the number "One" to distinguish it from the letter "Eye" or lower case "L".
- dboreham 6y ago
  This implies they were using the same character code for O,0 and l,1. Definitely not ASCII so perhaps some 5-channel code? IBM 716?
  - Someone 6y ago
    That was common on early typewriters. Examples: https://en.wikipedia.org/wiki/Sholes_and_Glidden_typewriter#/media/File%3ASholes-Glidden_1874.jpg https://en.wikipedia.org/wiki/Sholes_and_Glidden_typewriter#... https://www.reddit.com/r/typewriters/comments/2b4y0d/why_is_there_no_1_or_0_on_my_underwood_typewriter/ https://www.reddit.com/r/typewriters/comments/2b4y0d/why_is_...
fuzzfactor 6y ago
>How could things have flipped 180 degrees like that? Somebody other than IBM came along? IIRC electronic communication started with just ones & zeros then later got the rest of the numerals. Eventually they got (upper case only) alphabetic characters and by that time a plain zero had already been well established. Teletypes made sure the letter O always appeared different than the numeral zero. I never actually used Teletypes until the 1980s where we still got official cables by Telex. But even then a large number of experienced administrators had learned to type manually on traditional typewriter keyboards which are also hard to press but there was no zero or 1 key when they learned. It was important not to reflexively substitute letters for numbers, and if you did you needed to be able to tell the difference on paper. The ones they are talking about are some of the earliest ASCII Teletypes, where the numerals were wisely standardized equal to the least significant 4 bits out of their total of 7 bits. Zero is 0000, and upper case O coincidentally is 1111. IBM had its own standard before ASCII, apparently IBM printers produced a slashed upper case O before that. At Dartmouth it looks like the Teletype Model 35's they had were combining or overprinting the regular slash and zero fonts to make upper case O IBM style, and it appears their keyboards reflected the slashed output. The actual printouts show this. The main part of the documentation looks like the typical output of a manual electric IBM typewriter instead, where they slashed the O by backspacing. Looks even more funky compared to the real printout. Any typos would have been corrected the modern way, painting over them with Liquid Paper then retyping after it dried. The original printouts didn't always need to be actually cut with scissors & pasted into the document like lots of ordinary graphics since sometimes it was a whole page, they just manually typed a page number at the bottom and it got Xeroxed into its place. Others were probably cut with a paper cutter beforehand, not scissors. ASCII had early revisions about this time, within a few years I was a youngster in an office where we got one of the first "luggable" printing terminals and connected to a mainframe through a telephone modem over long-distance AT&T lines. With the suitcase model and acoustic coupler modems we could log in to the "host" with our "laptop" from clients' offices or residences to serve them with more computing power than anyone else around. These were some of the first that were made for computer use not for the Teletype network. Just an early RS-232 connector with 6-conductor cable to the DB-25 socket on the modem. RS-232B at first then RS-232C, still waiting for RS-232D, expected after they landed on the moon. They weren't quick enough and IBM put RS-232C on the desktop, called it a "COM" port and its been that way ever since. Well if you still want to have the remaining possibility of doing fully-backward-compatible serial communication, and without needing hardware-specific drivers to communicate with any vintage of computer or modem. This was the first time I saw the slashed zero, never the slashed upper case O. And it was a traditional non-typewheel mechanism, electically powered so the keyboard was not mechanical, but otherwise it made as much noise as a really fast hard-hitting typewriter, making multiple copies on modern carbonless triplicate rolls. People were amazed with new technology back then. Eventually with PC's a number of office people connected external modems to their standard COM ports to log into servers, usually plugged right into a modular Bell system phone jack rather than acoustically coupled to the standard telephone handset, plus autodialing became available. Their standard serial mouse was on their other COM port. If they had DOS software that supported a mouse, which was not yet common. As a web began to appear these were the only people already equipped to partake, but in the long run the net got popular and built-in modems were common expansion cards (later standard equipment way before RJ45 ethernet) which connect right to the phone jack without needing a physical COM port. Plus the next modems were built into the motherboards which all just had phone jacks for a while, mostly software modems.

alexjm 6y ago

I think I've seen some older content where the convention was reversed like this. Wikipedia's article on slashed zero claims that IBM and some other mainframes put their slash on the letter O instead of the number 0. However, in a bit of circularity, its citation (1) is this same BASIC manual. Checking an IBM manual (2) for punching cards, neither 0 nor O has a slash. The manual is undated, but documents the model 26 keypunch from 1949 and not the model 29 keypunch from 1964, so it's probably older than this BASIC manual. 1: https://en.wikipedia.org/wiki/Slashed_zero#cite_ref-9 https://en.wikipedia.org/wiki/Slashed_zero#cite_ref-9 2: https://archive.org/details/bitsavers_ibmpunchedAnIntroductiontoIBMPunchedCardDataProces_2436138/page/n5/mode/2up https://archive.org/details/bitsavers_ibmpunchedAnIntroducti... (page 4, 15)

Someone 6y ago
On IBM punched cards, the letters needn’t look very different, as you could always look at the punches (digits have only one punch; also look at the patterns for letters A-I, J-R, and S-Z) And yes, people learned that. Because the primary output of a puncher were the holes, not the printed text, maintenance of the ‘print’ part wasn’t always done well (ink smear or devices that ran out of ink), resulting in print output didn’t look remotely as clean as that manual shows.

8bitsrule 6y ago

That's a tough question. The slash-0 (for decimal zero) had been in use long before the BASIC and the ASR-33 came along. (In ham radio for one.) Dartmouth or Teletype may have had a reason for trying this ... but it didn't last! [Edit] OK, think I found the culprit. "The rule which has the letter O with a slash and the zero without was used at IBM and a few other early mainframe makers; this is even more of a problem for Scandinavians, because it looks like two of their letters at the same time." -- https://simple.wikipedia.org/wiki/Zero#Telling_zero_and_the_letter_O_apart https://simple.wikipedia.org/wiki/Zero#Telling_zero_and_the_...

dmolony 6y ago

I remember in 1976 we were using mark sense cards to write programs, and we definitely had to slash the letter O. I think we also had to slash the Z to distinguish it from a 7.

HarryHirsch 6y ago
I think the purpose of the Z-slash was to distinguish from the digit 2.

lsllc 6y ago

At least as early as 1977 the Commodore PET and the Apple ][ had "slashed zeros"; followed by the Atari 400/800 in 1979, the BBC Micro in 1981 and the Sinclair ZX Spectrum and Commodore 64 in 1982: https://damieng.com/blog/2011/02/20/typography-in-8-bits-system-fonts https://damieng.com/blog/2011/02/20/typography-in-8-bits-sys... Uh, ok. Turns out it was the 12th and 13th century that it was first known to have been used! https://en.wikipedia.org/wiki/Slashed_zero#Origins https://en.wikipedia.org/wiki/Slashed_zero#Origins

todd8 6y ago

In the 60's there was no consistent standard for this. I remember this being written about in the CACM 1967. Those with access to old copies of the Communications of the ACM can take a look at [1]. Here is the title and abstract: Towards standards for handwritten zero and oh: much ado about nothing (and a letter), or a partial dossier on distinguishing between handwritten zero and oh, by R.W. Bemer The Chairman of the ACM Standards Committee, Julien Green, has charged me with making “more effective use of CACM for communication … to get grass-roots opinions from the ACM membership.” This paper is the first attempt. A partial dossier on distinguishing between handwritten zero and the letter oh is assembled here. This presentation was triggered by a request for guidance in this matter presented by the United Kingdom Delegation to ISO/TC97/SC2, Character Sets and Coding, at the meeting in Paris on 1967 March 13-16. The matter is just now in the province of USASI X3.6, to which comments might be directed. Comments will be expected within sixty days [by approximately October 1st]. [1] https://dl.acm.org/doi/10.1145/363534.363563 https://dl.acm.org/doi/10.1145/363534.363563

todd8 6y ago

Many years ago I adopted the personal convention of using a slash for the number zero and a little curly cue at the top of the capital letter O. By using both in my handwriting where they could be confused, I was free to use just an unadorned letter or digit in situations where context made it clear. [1] Like the capital O found in the google font: https://fonts.google.com/specimen/Cedarville+Cursive?category=Handwriting&preview.text=big%20O&preview.text_type=custom https://fonts.google.com/specimen/Cedarville+Cursive?categor...