Pin header

A pin header (or simply header) is a form of electrical connector. It consists of one or more rows of male pins typically spaced 2.54 millimetres (0.1 in) apart, but sometimes 2 millimetres (0.079 in) or 1.27 millimetres (0.05 in) is used as well. The distance between pins is commonly referred as pitch in the electronic community.

Overview

Pin headers are often associated with ribbon cable connectors, pin headers often also function as recipients for jumpers. The most common jumper spacing is 0.1 inches (2.54 mm) spacing, though 2 millimetres (0.079 in) is sometimes used in smaller products.

Pin header connectors are thus "male" connectors (female counterparts do exist, but these are normally just called "header connectors", without "pin") and are mostly used inside equipment, rather than being used as a connector on the outside of the device.

Normally pin headers are pin through hole (PTH) devices, but surface-mount technology (SMT) versions of one and two row pin headers also exist. In the latter case the solder sides of the pins are simply bent on a 90 degree angle so as to be soldered to a solder plane. On single row pin headers the pins are bent alternating to one side or the other, on dual row pin headers the pins are simply bent outwards. If pin headers are optional, the PTH variant is often chosen for ease of manual assembly. Pin headers can be either straight or angled. The latter form is often used to connect two boards together.

Environment variable

Environment variables are a set of dynamic named values that can affect the way running processes will behave on a computer.

They are part of the environment in which a process runs. For example, a running process can query the value of the TEMP environment variable to discover a suitable location to store temporary files, or the HOME or USERPROFILE variable to find the directory structure owned by the user running the process.

They were introduced in their modern form in 1979 with Version 7 Unix, so are included in all Unix operating system flavors and variants from that point onward including Linux and OS X. From PC DOS 2.0 in 1982, all succeeding Microsoft operating systems including Microsoft Windows, and OS/2 also have included them as a feature, although with somewhat different syntax, usage and standard variable names.

Details

In all Unix and Unix-like systems, each process has its own separate set of environment variables. By default, when a process is created, it inherits a duplicate environment of its parent process, except for explicit changes made by the parent when it creates the child. At the API level, these changes must be done between running fork and exec. Alternatively, from command shells such as bash, a user can change environment variables for a particular command invocation by indirectly invoking it via env or using the ENVIRONMENT_VARIABLE=VALUE <command> notation. All Unix operating system flavors, DOS, and Windows have environment variables; however, they do not all use the same variable names. A running program can access the values of environment variables for configuration purposes.

Header (computing)

In information technology, header refers to supplemental data placed at the beginning of a block of data being stored or transmitted. In data transmission, the data following the header are sometimes called the payload or body.

It is vital that header composition follow a clear and unambiguous specification or format, to allow for parsing.

Examples

Headwind and tailwind

A tailwind is a wind that blows in the direction of travel of an object, while a headwind blows against the direction of travel. A tailwind increases the object's speed and reduces the time required to reach its destination, while a headwind has the opposite effect. Tailwinds and headwinds are commonly measured in relation to the speed of vehicles — commonly air and watercraft — as well as in running events — particularly sprints.

In aeronautics, a headwind is favorable in takeoffs and landings because an airfoil moving into a headwind is capable of generating greater lift than the same airfoil moving through tranquil air or a tailwind at equal ground speed. As a result, aviators and air traffic controllers commonly choose to take off or land in the direction of a runway that will provide a headwind. In sailing, a headwind may make forward movement difficult, and necessitate tacking into the wind.

Aeronautics calculations

Headwind component

Pilots calculate the Headwind Component, Tailwind Component and Crosswind Component of any wind, if they do exist. The direction of wind is calculated using wind sock. Headwind and Tailwind are cosine functions of the wind while Crosswind Component is a sine function. Headwind and Tailwind do not occur together in normal conditions. Determining the ground speed of an aircraft requires the calculation of the head or tailwind.

Łępin

Łępin [ˈwɛmpin] is a village in the administrative district of Gmina Stara Błotnica, within Białobrzegi County, Masovian Voivodeship, in east-central Poland. It lies approximately 15 kilometres (9 mi) south of Białobrzegi and 78 km (48 mi) south of Warsaw.

The village has a population of 148.

References

Coordinates: 51°30′58″N 20°58′1″E / 51.51611°N 20.96694°E / 51.51611; 20.96694

Pin (computer program)

Pin is a platform for creating analysis tools. A pin tool comprises instrumentation, analysis and callback routines. Instrumentation routines are called when code that has not yet been recompiled is about to be run, and enable the insertion of analysis routines. Analysis routines are called when the code associated with them is run. Callback routines are only called when specific conditions are met, or when a certain event has occurred. Pin provides an extensive application programming interface (API) for instrumentation at different abstraction levels, from one instruction to an entire binary module. It also supports callbacks for many events such as library loads, system calls, signals/exceptions and thread creation events.

Pin performs instrumentation by taking control of the program just after it loads into the memory. Then just-in-time recompiles (JIT) small sections of the binary code using pin just before it is ran. New instructions to perform analysis are added to the recompiled code. These new instructions come from the Pintool. A large array of optimization techniques are used to obtain the lowest possible running time and memory use overhead. As of June 2010, Pin's average base overhead is 30 percent (without running a pintool).

Pin (bridge)

In bridge and similar trick-taking games, the term pin refers to the lead of a higher card from one hand to capture a singleton of lower rank in an opponent's hand.

Example

South wants five tricks from this suit. If the opponents' cards split 3-2 and they defend rationally, South must lose at least one trick – dropping a singleton king won't help South. However, if East holds the singleton jack then South can begin by lead the queen and pinning the jack. Provided declarer can re-enter his hand at least once, he can then take up to two finesses to capture the king.

The tactic is also available to the defense, but it is more difficult to find when declarer holds the singleton.

References