For a few $ more

The dollar sign aka the peso sign, $¹ is a currency symbol used to indicate the unit of various currencies around the world, including most currencies denominated “dollar” or “peso”.

Computers & Keyboards

Because of its use in early American computer applications such as business accounting, the $ sign is almost universally present in computer character sets. The most interesting fact in the computing and programming world is that the $ is appropriated for many purposes unrelated to money.

The $ plays a prominent character in programming languages that any Keyboard without the $ or replaced with another character would be detrimental to most programmers.

Via Wikipedia, here are a few instances;

• BASIC: $ is appended to a variable name to define that variable’s data type as a character string, for example, H$="Hello, world!".
• PHP: $ is prefixed to names to define variables.
• Perl: $ defines scalar variables.
• Ruby: $ defines global variables.
• In *nix shells and many other programming languages such as Perl, JavaScript, C#, Scala, Groovy and Kotlin, $ introduces an expression that should be evaluated to yield text.
• Java and Python uses $ to mark the place where the result of an expression elsewhere should be inserted into text.
• Delphi uses $ to define hexadecimal constants.
• $ is used in the ALGOL 68 language to delimit transput format regions.
• TeX uses $ to delimit mathematical regions.
• FORTRAN 66 uses $ as an alternative to a quotation mark for delimiting strings.
• PL/M: $ can be used to put a visible separation between words in compound identifiers.
• Haskell: $ is used as a function application operator.
• In an AutoHotkey script, a hotkey declared with $ is not triggered by a Send command elsewhere in the script.
• The jQuery library defines $ as its main symbol, primarily as a function that queries a web page for one or more HTML elements, but also with other utilities attached to it as properties like $.ajax. The Prototype.js library defines it similarly for querying.
• ASP.NET: $ used in a tag in the web page indicates an expression will follow it. The expression that follows is .NET language-agnostic, as it will work with C#, VB.NET, or any CLR supported language.
• Erlang: $ precedes character literals.
• COBOL: $ sign is used in the Picture clause to depict a floating currency symbol as the left most character.
• In some assembly languages, such as MIPS, $ is used to represent registers.
• In Honeywell 6000 series assembler, $, when used as an address, meant the address of the instruction in which it appeared.
• CMS-2: $ is used as a statement terminator.
• R: $ is used as a subsetting operator.
• Q: $ is used as a casting/padding/enumeration/conditional operator.
• Sass: $ is prefixed to define a variable.
• Svelte: $ can be used to mark reactive statements.
• DOS: $ marks the end of text displayed with system function 9.
• In Microsoft Windows, $ is appended to the share name to hide a shared folder or resource. For example, \\server\share will be visible to other computers on a network, while \\server\share$ will be accessible only by explicit reference.
• In the LDAP directory access protocol, $ is used as a line separator in various standard entry attributes such as postalAddress.
• In the UNIVAC EXEC 8 operating system, $ means “system”.
• In RISC OS, $ is used in system variables to separate the application name from the variables specific to that application. For example Draw$Dir specifies the directory where the !Draw application is located. It is also used to refer to the root directory of a file system.
• Microsoft Excel and other spreadsheet software use $ to denote a fixed row, fixed column reference, or an absolute cell reference.
• $ matches the end of a line or string in sed, grep, and POSIX and Perl regular expressions, as well as the end of a line or the file in text editors ed, ex, vi, pico, and derivatives.
• In extended Markdown that supports Mathematical functions tend to use the $ as beginning and ending delimiters.

Fun Fact

I was today years old learning that the $ symbol is used as the unit of reactivity for nuclear reactors — 0$ being the threshold of slow criticality (steady reaction rate) while 1$ is the threshold of prompt criticality (nuclear excursion or explosion).