The Elegance of the ASCII Table • Hacker News Board

Re: The Elegance of the ASCII Table

#41

Post by userbinator » Tue, Jul 23, 2024, 4:04 AM UTC

You might be familiar with carriage return (0D) and line feed (10)

You mean 0D and 0A, or 13 and 10, but that mix of base really stood out to me in an otherwise good article. I'm one of numerous others who have memorised most of the base ASCII table, and quite a few of the symbols as well as extended ASCII (CP437), mainly because it comes in handy for reading programs without needing a disassembler. Those who do a lot of web development may find the sequence 3A 2F 2F familiar too, as well as 3Ds and 3Fs.

I can see the rationale for being in that order, but [\] and {|} are less obvious, as well as why their position is 1 column to the left of .

Re: The Elegance of the ASCII Table

#42

Post by EvanAnderson » Tue, Jul 23, 2024, 4:12 AM UTC

theamk wrote: post #29

EvanAnderson wrote: post #20

Earlier quoted context omitted.

I did some ETL work that used the ASCII delimiter characters. It was very enjoyable. I didn't have to worry about escaping or parsing escaped strings. The control codes were guaranteed to be illegal in input. It was refreshing.

Could you do the same with TSV? A lot of datasets can either prohibit tabs in data, or convert it to spaces in early ingestion.

TSV is a joy compared to CSV, for sure. CLI tools that output TSV are what immediately spring to mind.

Re: The Elegance of the ASCII Table

#43

Post by KingOfCoders » Tue, Jul 23, 2024, 4:20 AM UTC

For everyone who doesn't need ä,ü,ö. Or software that needs to take ä,ü,ö. For everyone else, UTF is a blessing.

Re: The Elegance of the ASCII Table

#44

Post by kazinator » Tue, Jul 23, 2024, 4:32 AM UTC

jolmg wrote: post #10

> So when you’re reading 7-bit ASCII, if it starts with 00, it’s a non-printing character. Otherwise it’s a printing character. > The first printing character is space; it’s an invisible character, but it’s still one that has meaning to humans, so it’s not a control character (this sounds obvious today, but it was actually the source of some semantic argument when the ASCII standard was first being discussed). Hmm..…

Space doesn't just move the cursor on a display; it will obliterate a character cell with a space glyph.

When a display terminal has nondestructive backspace (backspace character doesn't erase), it can be software emulated with BS-SPACE-BS.

At your Linux terminal, you can do "stty echoe" (echo erase) to turn this on (affecting the echoing of backspace characters that are input, not all backspace characters).

Dial-up BBSes had this as a configurable setting also.

Re: The Elegance of the ASCII Table

#45

Post by rob74 » Tue, Jul 23, 2024, 4:40 AM UTC

pwg wrote: post #14

jolmg wrote: post #10

> So when you’re reading 7-bit ASCII, if it starts with 00, it’s a non-printing character. Otherwise it’s a printing character. > The first printing character is space; it’s an invisible character, but it’s still one that has meaning to humans, so it’s not a control character (this sounds obvious today, but it was actually the source of some semantic argument when the ASCII standard was first being discussed). Hmm..…

You also have to keep in mind the "interface" for 1962-1968. The printer teletype machine. The "control codes" were to "control" the printhead. So "carriage return" meant move the "print carriage" back to the left margin. "New line" meant move the paper platen one line height of rotation to move the paper to the next line. In that context, "back space" was "move print head one space left" (rather more like a "reverse…

> For those typewriters with built in correction tape options (at least some IBM Selectric models, possibly more) the typewriter would retype the character using the "white-out" ribbon

there was also a solution for cheaper typewriters: small sheets of "white-out" paper (known under the genericized brand name "Tipp-Ex" here in Germany) that you could hold between the ink ribbon and the paper to "overwrite" a typo.

Re: The Elegance of the ASCII Table

#46

Post by blahedo » Tue, Jul 23, 2024, 4:45 AM UTC

Another piece of elegance: by putting the uppercase letters in the block beginning at 0x40 (well, 0x41) it means that all the control codes at the start of the table line up with a letter (or one of a small set of other punctuation: @[\]^_), giving both a natural shorthand visual representation and a way to enter them with an early keyboard, by joining the pressing of the letter with... the Control key. Control-M (often written ^M) is carriage return because carriage return is 0x0D and M is 0x4D.

Re: The Elegance of the ASCII Table

#47

Post by fsckboy » Tue, Jul 23, 2024, 4:56 AM UTC

ggm wrote: post #8

man ascii is never far from my fingers. combined with od -c and od -x it gets the job done. I don't think as fluently in Octal as I used to. Hex has become ubiquitous.

you mean ?

    ascii

Re: The Elegance of the ASCII Table

#48

Post by sixothree » Tue, Jul 23, 2024, 5:06 AM UTC

thristian wrote: post #24

> That, I’m afraid, is because ASCII was based not on modern computer keyboards but on the shifted positions of a Remington No. 2 mechanical typewriter – whose shifted layout was the closest compromise we could find as a standard at the time, I imagine. According to Wikipedia¹, American typewriters were pretty consistent with keyboard layout until the IBM Selectric electric typewriter. Apparently "small" characters (…

I never realized my first computer used ascii directly for the shifted number keys.

https://en.wikipedia.org/wiki/TRS-80_Color_Computer#/media/F...

Re: The Elegance of the ASCII Table

#49

Post by bigstrat2003 » Tue, Jul 23, 2024, 5:08 AM UTC

KingOfCoders wrote: post #43

For everyone who doesn't need ä,ü,ö. Or software that needs to take ä,ü,ö. For everyone else, UTF is a blessing.

Which, given the people who designed this and the time they were designing for, was most of them (and most of their audience). Don't confuse "this old standard doesn't adequately cover all cases today" with "this old standard sucked at the time".

Re: The Elegance of the ASCII Table

#50

Post by kmoser » Tue, Jul 23, 2024, 5:25 AM UTC

EvanAnderson wrote: post #18

pwg wrote: post #14

Earlier quoted context omitted.

You also have to keep in mind the "interface" for 1962-1968. The printer teletype machine. The "control codes" were to "control" the printhead. So "carriage return" meant move the "print carriage" back to the left margin. "New line" meant move the paper platen one line height of rotation to move the paper to the next line. In that context, "back space" was "move print head one space left" (rather more like a "reverse…

> The article stated why DEL is where it is (all ones) -- so that for punched paper tape, one could get a punch-out of every position... I saw an analogous use of backspace on some OS I ran into 30 years ago cruising around either Tymnet or TELENET. (I wish I could remember the OS...) The password prompt assumed local echo. After entering a password the host would send a series of backspaces and various patterns of c…

On the login to the first timesharing system I used, it would prompt for your password, then type eight M's, W's, and X's on top of each other (on paper, of course, since this was using a Teletype terminal), so when you actually typed your password the characters would be printed on top of those already obscured lines.