Reg
Reg or REG may refer to:
Places
See also
Windows Registry
The Windows Registry is a hierarchical database that stores low-level settings for the Microsoft Windows operating system and for applications that opt to use the Registry. The kernel, device drivers, services, Security Accounts Manager (SAM), and user interface can all use the Registry. The Registry also allows access to counters for profiling system performance.
When introduced with Windows 3.1, the Windows Registry primarily stored configuration information for COM-based components. Windows 95 and Windows NT extended its use to rationalise and centralise the information in the profusion of INI files, which held the configurations for individual programs, and were stored at various locations. It is not a requirement for Windows applications to use the Windows Registry. For example, .NET Framework applications use XML files for configuration, while portable applications usually keep their configuration files with their executable.
Rationale
Regular expression
In theoretical computer science and formal language theory, a regular expression (sometimes called a rational expression) is a sequence of characters that define a search pattern, mainly for use in pattern matching with strings, or string matching, i.e. "find and replace"-like operations. The concept arose in the 1950s, when the American mathematician Stephen Kleene formalized the description of a regular language, and came into common use with the Unix text processing utilities ed, an editor, and grep, a filter.
In modern usage, "regular expressions" are often distinguished from the derived, but fundamentally distinct concepts of regex or regexp, which no longer describe a regular language. See below for details.
Regexps are so useful in computing that the various systems to specify regexps have evolved to provide both a basic and extended standard for the grammar and syntax; modern regexps heavily augment the standard. Regexp processors are found in several search engines, search and replace dialogs of several word processors and text editors, and in the command lines of text processing utilities, such as sed and AWK.
