Tilde ~

Being a Microsoft developer for nearly 8 years now has caused me to miss out on some very interesting OSI (Open Source Initiative) development. Now that licensing and many other issues are becoming exceedingly difficult to maintain on a decent level (financially), this Lone Ranger developer is looking into other avenues for his development platform: Namely, Ruby on Rails. I must say, this is some of the most exciting development I’ve dove into in a long time! Do you have any idea how much money I can save on my development platform and IDE by programming in Ruby? Thousands, no, hundreds of thousands! No joke! Visual Studio 2005 (my development environment) costs me a measly $1200 for a single license. SQL Server 2005 is many thousands, and Windows 2003 Server is more many thousands… It goes on and on and on… At either rate, as I learn new technologies, I’m coming across things (such as this tilde thingy) that I’ve seen in the past but have never needed to know anything about until now.

This is the Computing excerpt from Wiki on what this little guy means:

Directories and URLs

In Unix shells, the tilde indicates the current user’s home directory (e.g., /home/username). When prepended to a particular username, it indicates that user’s home directory (e.g., ~janedoe for the home directory of user janedoe, typically /home/janedoe). When some Unix shell commands overwrite a file, they can be made to keep a backup by renaming the original file as filename~.

Used in URLs on the World Wide Web, it often denotes a personal website on a Unix-based server. For example, http://www.example.com/~johndoe/ might be the personal web site of John Doe. This mimics the Unix shell usage of the tilde. However, when accessed from the web, file access is usually directed to a subdirectory in the user’s home directory, such as /home/username/public_html or /home/username/www.

In URLs, the characters %7E (or %7e) may substitute a tilde if an input device lacks a tilde key. Thus, http://www.example.com/~johndoe/ and http://www.example.com/%7Ejohndoe/ are essentially the same URL.

Computer languages

It is used in the Perl programming language as part of the pattern match operators for regular expressions:

• $a =~ /regex/ returns true if the variable is matched.
• $a !~ /regex/ returns false if the variable is matched.

The popularity of Perl’s regular expression and syntax has led to the use of these operators in other programming languages, such as Ruby.

In the C and C++ programming languages, the tilde character is used to invert all bits of an integer, following the notation in logic. In C++, the tilde is also used as the first character in a class’s method name (where the rest of the name must be the same name as the class) to indicate a destructor – a special method which is called at the end of the object’s life.

In the D programming language, the tilde is used as an array concatenation operator, as well as to indicate an object destructor.

In the CSS stylesheet language, the tilde is used for the indirect adjacent combinator as part of a selector.

In the Inform programming language, the tilde is used to indicate a quotation mark inside a quoted string.

In “text mode” of the LaTeX typesetting language a stand-alone tilde can be obtained with \~{} and for use as a diacritics, e.g., like \~{n} rendering “ñ”. In “math mode” a stand-alone tilde can be written as \tilde{~} and as diacritics, e.g., \tilde{x}. For a wider tilde the \widetilde can be used. The \sim command produce a tilde-like character that is often used in probability mathematical equations, and the double-tilde is obtained with \approx. In both text and math mode a tilde on its own (~) is rendering a white space with no line breaking.

The Emacs text editor forms the names used for backup files by appending a tilde to the original file name.

Microsoft filenames

The tilde was part of Microsoft’s name mangling scheme when it developed the VFAT filesystem. This upgrade introduced long filenames to Microsoft Windows, and permitted additional characters (such as the space) to be part of filenames, which were prohibited in previous versions. Programs written prior to this development could only access filenames in the so-called 8.3 format—the filenames consisted of a maximum of eight alphanumeric characters, followed by a period, followed by three more alphanumeric characters. In order to permit these legacy programs to access files in the VFAT filesystem, each file had to be given two names—one long, more descriptive one, and one that conformed to the 8.3 format. This was accomplished with a name-mangling scheme in which the first six characters of the filename are followed by a tilde and a digit. For example, “Program Files” becomes “PROGRA~1“.

Other uses

In most online computer games, tilde (located below the Escape key on US keyboards, a key is nevertheless in the same location on other layouts that serves the same function) can be used to bring down the console. This will allow cheating, seeing previous scores, or chat logs.

Computer programmers use the tilde in various ways and often call the symbol (as opposed to the diacritic) a squiggle or a twiddle. According to the Jargon File, other synonyms sometimes used in programming include not, approx, wiggle, enyay (after eñe) and (humorously) sqiggle.

See History of the tilde for a history of how the tilde came to become part of the standard computer character sets.

In Google search, the tilde entered before a search query word displays listings with that word and synonyms of it. [1]

To type a tilde on a Spanish keyboard, you can use AltGr+4. On the Macintosh keyboard, Option-n followed by another letter places the tilde over that letter.

Octothorpe #

Did you know that the ‘#’ symbol is actually officially called the octothorpe?

More names: Comment sign, crosshatch, crunch, fence, gate, grid, gridlet, hash, hash mark, hash sign, hex, mesh, octothorn, octalthorpe, octothorp, octothorpe, octatherp, pig pen, pound, pound sign, sharp, space sign, splash, square, widget mark.

So many names for such a small glyph!

Octothorpe; octo (eight points) & thorpe (named for Jim Thorpe, why, I know not.)

Interesting. I’ve always called it a pound sign or bash. I suppose I derived bash from a combination of the UNIX equivalents ‘#!’ – to say ‘hash bang’.

What do YOU call it?