Hg

In other uses:

See also

Inch of mercury

Inches of mercury, (inHg and "Hg) is a unit of measurement for pressure. It is still used for barometric pressure in weather reports, refrigeration and aviation in the United States.

It is defined as the pressure exerted by a circular column of mercury of 1 inch in height at 32 °F (0 °C) at the standard acceleration of gravity.

Aircraft altimeters measure the relative pressure difference between the lower ambient pressure at altitude and a calibrated reading on the ground. Within the U.S. and Canada, these readings are provided in inches of mercury. Ground readings vary with weather and along the route of the aircraft as it travels, so current readings are relayed periodically by air traffic control. Aircraft operating at higher altitudes (at or above what is called the transition altitude, which varies by country) set their barometric altimeters to a standard pressure of 29.92 inHg (1 atm = 29.92 inHg) or 1013.25 hPa (1 hPa = 1 mbar) regardless of the actual sea level pressure. The resulting altimeter readings are known as flight levels.

Mercurial

Mercurial is a cross-platform, distributed revision control tool for software developers. It is mainly implemented using the Python programming language, but includes a binary diff implementation written in C. It is supported on MS Windows and Unix-like systems, such as FreeBSD, Mac OS X and Linux. Mercurial is primarily a command line program but graphical user interface extensions are available. All of Mercurial's operations are invoked as arguments to its driver program hg, a reference to the chemical symbol of the element mercury.

Mercurial's major design goals include high performance and scalability, decentralized, fully distributed collaborative development, robust handling of both plain text and binary files, and advanced branching and merging capabilities, while remaining conceptually simple. It includes an integrated web interface. Mercurial has also taken steps to ease the transition for users of other version control systems, particularly Subversion.

The creator and lead developer of Mercurial is Matt Mackall. Mercurial is released as free software under the terms of the GNU GPL v2 (or any later version).