## antenna gain

The factor by which a radio antenna of a given shape focusses the emitted power into a smaller beamwidth compared with an omnidirectional antenna.

Last updated: 2008-02-26

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## Anthony Hoare

<person>

(C. Anthony R. Hoare, Tony) A computer scientist working on programming languages, especially parallel ones. Hoare was responsible for Communicating Sequential Processes (CSP).

[Did he invent the Hoare powerdomain? Other details?]

Last updated: 1999-07-22

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## anti-aliasing

<graphics>

A technique used on a grey-scale or colour bitmap display to make diagonal edges appear smoother by setting pixels near the edge to intermediate colours according to where the edge crosses them.

The most common example is black characters on a white background. Without anti-aliasing, diagonal edges appear jagged, like staircases, which may be noticeable on a low resolution display. If the display can show intermediate greys then anti-aliasing can be applied. A pixel will be black if it is completely within the black area, or white if it is completely outside the black area, or an intermediate shade of grey according to the proportions of it which overlap the black and white areas. The technique works similarly with other foreground and background colours.

"Aliasing" refers to the fact that many points (which would differ in the real image) are mapped or "aliased" to the same pixel (with a single value) in the digital representation.

Last updated: 1998-03-13

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## antichain

A subset S of a partially ordered set P is an antichain if,

``` for all x, y in S,  x <= y  =>  x = y

```
I.e. no two different elements are related.

("<=" is written in LaTeX as \subseteq).

Last updated: 1995-02-03

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## antisymmetric

A relation R is antisymmetric if,

``` for all x and y,  x R y and y R x  =>  x == y.

```
I.e. no two different elements are mutually related.

Partial orders and total orders are antisymmetric. If R is also symmetric, i.e.

``` x R y  =>  y R x

```
then

``` x R y  =>  x == y

```
I.e. different elements are not related.

Last updated: 1995-04-18

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## antivirus

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## antivirus program

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## antivirus software

<tool>

Programs to detect and remove computer viruses. The simplest kind scans executable files and boot blocks for a list of known viruses. Others are constantly active, attempting to detect the actions of general classes of viruses. antivirus software should always include a regular update service allowing it to keep up with the latest viruses as they are released.

Last updated: 1998-02-25

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## ANTLR

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