# and what the heck is a "¬" **URL:** \ **Category:** Factual Questions\ **Created:** [October 8, 2003, 10:00am UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261 "2003-10-08T10:00:16Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![jimdigritz](https://avatars.discourse-cdn.com/v4/letter/j/91b2a8/32.png) [@jimdigritz](https://boards.straightdope.com/u/jimdigritz)\ **Post date:** [October 8, 2003, 10:00am UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/1 "2003-10-08T10:00:16Z")
surely it has _some_ purpose… other than to play ascii Tetris? ---
**Author:** ![Burton\_Radons](https://avatars.discourse-cdn.com/v4/letter/b/c89c15/32.png) [@Burton\_Radons](https://boards.straightdope.com/u/Burton_Radons)\ **Post date:** [October 8, 2003, 10:42am UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/2 "2003-10-08T10:42:10Z")
That is a logical symbol meaning not. Oh, and [UNICODE](http://www.unicode.org/charts/) lists the “`” key as a grave accent. This makes the most sense, since “~” and “^” are also interpretable as accents. Why the keyboards have these is beyond me, since as far as I know there have never been programs that exploit this potential character marking, such as with Pi~nata. Also, the “|” is a broken bar, although in recent years it’s become a straight pipe. UNICODE says it’s a parted rule in typography. I think it’s great to change it to a straight pipe, because there aren’t enough indistinguishable vertical characters in English. ---
**Author:** ![jimdigritz](https://avatars.discourse-cdn.com/v4/letter/j/91b2a8/32.png) [@jimdigritz](https://boards.straightdope.com/u/jimdigritz)\ **Post date:** [October 8, 2003, 10:45am UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/3 "2003-10-08T10:45:55Z")
Thanks Burton, also does the ~ tilda also mean ‘circa’ or ‘approximately’ in logic formulas? ---
**Author:** ![Burton\_Radons](https://avatars.discourse-cdn.com/v4/letter/b/c89c15/32.png) [@Burton\_Radons](https://boards.straightdope.com/u/Burton_Radons)\ **Post date:** [October 8, 2003, 11:05am UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/4 "2003-10-08T11:05:14Z")
I hesitate to say it means anything, since languages use these ambiguous characters in different ways (for example, many use a single | as a logical OR). In C and C++, the ~ is a bitwise invert; all bits that are true are made false and vice versa. The trouble with having any circa equivalence operator is that the appropriate epsilon (the minimum difference to register distinct values) changes depending upon the context. When we write that in an equation we leave that value to reader interpretation; with computers we need a value, which is an arbitrary choice. It’s better to leave such an operation to a function where the parameters can be explicitly and unambiguously defined. That said, the most common epsilon is 0.000001, or 1e-6. As far as I know this is just a tradition. ---
**Author:** ![John\_W.Kennedy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_w.kennedy/32/1031_2.png) [@John\_W.Kennedy](https://boards.straightdope.com/u/John_W.Kennedy)\ **Post date:** [October 8, 2003, 1:46pm UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/5 "2003-10-08T13:46:52Z")
Various programming languages over the years have used ~, !, ^, and ¬ for NOT, all reflecting the fact that, until the 90’s, computers did not normally have ≠, ≮, or ≯ (that’s not-equal, not-less, and not-greater), or the ability to draw a line over a symbol (a common way in logic of expressing NOT). I don’t know offhand of any computer language with a “circa” symbol, although _some_ languages, like APL, contain “circa” in their definitions of “equal”. (For those who are not programmers, and think that’s bizarre, the reason is that computers _cannot_ carry fractions out to infinity, so most scientific calculations _require_ that tests for equality be approximate. Most languages assume that the programmer will undertake the burden of defining just how equal “equal” should be, but a few figure it might as well be automatic.) The ~, `, ^, and ’ keys are used in international keyboards to make accents, as is ", which is used to make a dieresis: ã, à, â, á, ä. Since ASCII was originally designed for real, printing teletypes, I imagine some such use was intended from the beginning, since, of course, a typewriter-style overstrike was entirely possible. (And, yes, boys and girls, back in the days of real typewriters, " was the accepted way to make a dieresis on an English-language typewriter.) In several points, ASCII code is based on the keyboard of US manual (not electric) typewriters. ---
**Author:** ![C\_K\_Dexter\_Haven](https://avatars.discourse-cdn.com/v4/letter/c/b2d939/32.png) [@C\_K\_Dexter\_Haven](https://boards.straightdope.com/u/C_K_Dexter_Haven)\ **Post date:** [October 8, 2003, 5:51pm UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/6 "2003-10-08T17:51:52Z")
This isn’t a comment on a Staff Report (except by a very tortuous connection), so I’m moving it to the General Questions format. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [October 8, 2003, 7:19pm UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/7 "2003-10-08T19:19:29Z")
In formal logic, ~ is an alternate symbol for negation. It’s a synonym for ¬. ---
**Author:** ![Shade](https://avatars.discourse-cdn.com/v4/letter/s/2bfe46/32.png) [@Shade](https://boards.straightdope.com/u/Shade)\ **Post date:** [October 8, 2003, 10:54pm UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/8 "2003-10-08T22:54:13Z")
In other parts of maths ~ means “tends to a ratio of one with” eg. n(n-1)~n[sup]2[/sup]. IIRC I’ve also seen it used to mean ‘about’ or ‘something like’, though for ‘approximately’ we’ve normally used a tilde with a bar underneath, or a wavey equals sign. But the notation does vary so YMMV. ---
**Author:** ![TJdude825](https://avatars.discourse-cdn.com/v4/letter/t/dec6dc/32.png) [@TJdude825](https://boards.straightdope.com/u/TJdude825)\ **Post date:** [October 8, 2003, 11:02pm UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/9 "2003-10-08T23:02:19Z")
No, no! You’re all wrong. It’s just for making “AzN” emoticons. For example: ```auto ¬ ¬ v ``` Aren’t you glad we have teenage dopers? ---
**Author:** ![richardb](https://avatars.discourse-cdn.com/v4/letter/r/96bed5/32.png) [@richardb](https://boards.straightdope.com/u/richardb)\ **Post date:** [October 8, 2003, 11:04pm UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/10 "2003-10-08T23:04:46Z")
In the Macromedia Director programming language called “Lingo,” the ¬ symbol is used to allow command lines to split into two lines. ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [October 8, 2003, 11:05pm UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/11 "2003-10-08T23:05:38Z")
here’s what the encyclopedia of symbols has to say about the tilde: [http://www.symbols.com/encyclopedia/14/141.html](http://www.symbols.com/encyclopedia/14/141.html) ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [October 8, 2003, 11:31pm UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/12 "2003-10-08T23:31:36Z")
Also, ~ is used to indicate an equivalence relation (as in a ~ b to mean “a is equivalent to b”). ---
**Author:** ![dakravel](https://avatars.discourse-cdn.com/v4/letter/d/85e7bf/32.png) [@dakravel](https://boards.straightdope.com/u/dakravel)\ **Post date:** [October 10, 2003, 6:10am UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/13 "2003-10-10T06:10:30Z")
The grave accent ( " ` " ) is used in some Linux systems as a way to tell the system that the text inside of the graves is a command that should be run. Useful for scripting and the SED command. The pipe ( " | " ) is used to move the output of one command to the input of another. It allows one to do pretty much anything by combining all the basic commands. For Symbolic Logic, the tilda ( " ~ " ) is the most commonly used way to indicate negation. You can sometimes write a bar over the negated quantity, but that’s less common. ---
**Author:** ![Shalmanese](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shalmanese](https://boards.straightdope.com/u/Shalmanese)\ **Post date:** [October 10, 2003, 12:38pm UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/14 "2003-10-10T12:38:23Z")
If you set your keyboard to International rather than US101, whenever you type a ~n or `a, it will automatically convert it to the appropriate accented symbol for you. ---
**Author:** ![Patty\_O\_Furniture](https://avatars.discourse-cdn.com/v4/letter/p/96bed5/32.png) [@Patty\_O\_Furniture](https://boards.straightdope.com/u/Patty_O_Furniture)\ **Post date:** [October 10, 2003, 12:45pm UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/15 "2003-10-10T12:45:18Z")
It’s a nose. Regard: ¦:¬þ ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [October 14, 2003, 6:48am UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/16 "2003-10-14T06:48:14Z")
This is odd … on the main “General Questions” screen listing all the thread topics, I see that character as a line with a little hook at the end, like so (in crude ASCII art): ```auto ______ | ``` But when reading the thread, it is displayed as something that resembles a crushed and crumpled lower-case r, or possibly t. I wonder what’s up with that. ---
**Author:** ![jovan](https://avatars.discourse-cdn.com/v4/letter/j/0ea827/32.png) [@jovan](https://boards.straightdope.com/u/jovan)\ **Post date:** [October 14, 2003, 7:40am UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/17 "2003-10-14T07:40:43Z")
> [@](#): > > \*Originally posted by chorpler \* > \*\*But when reading the thread, it is displayed as something that resembles a crushed and crumpled lower-case r, or possibly t. I wonder what’s up with that. \*\* Does it look anything like [this?](http://web.mit.edu/jpnet/ji/data/0568.html) For some reason, the SDMB often loads up as a Japanese page when Japanese fonts are installed. This isn’t a problem usually, unless two-byte characters are used, in which case the characters are displayed as Japanese characters. On my computer the symbol shows up as katakana “ya”. For some reason. I just mention this because “ya” could be construed to look like a crumpled r or t. ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [October 14, 2003, 9:20am UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/18 "2003-10-14T09:20:21Z")
Yep, that’s the one, **Jovan**. I think I did install Japanese character support a while back, so I guess that explains it and other characters that are weird. For instance, the very first letter of **Attrayant** ’s emoticon-face looks, to me, like a reversed F with the bottom half (the part of the vertical line below the two horizontal bars) curved. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [October 14, 2003, 11:58am UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/19 "2003-10-14T11:58:11Z")
> [@](#): > > \*Originally posted by Burton Radons \* > \*\*That is a logical symbol meaning not. > > Oh, and [UNICODE](http://www.unicode.org/charts/) lists the “`” key as a grave accent. This makes the most sense, since “~” and “^” are also interpretable as accents. Why the keyboards have these is beyond me, since as far as I know there have never been programs that exploit this potential character marking, such as with Pi~nata.\*\* I’m confused. You don’t mean there are no programs that turn ~+n into ñ do you? Cause all the text editing programs I have do that. They also turn `+e into è, ¨+a into ä, ^+o into ô and so on and so forth. Oh, :smack: maybe you’re being sarchastic and I’m being dense. Sorry, carry on. (and use some smileys next time 😃 ) ---
**Author:** ![jovan](https://avatars.discourse-cdn.com/v4/letter/j/0ea827/32.png) [@jovan](https://boards.straightdope.com/u/jovan)\ **Post date:** [October 14, 2003, 12:11pm UTC](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261/20 "2003-10-14T12:11:14Z")
What program are you talking about? Word 2000 won’t do that for me. [Next page](https://boards.straightdope.com/t/and-what-the-heck-is-a/206261.md?page=2)