compact

<theory>

1. (Or "finite", "isolated") In domain theory, an element d of a cpo D is compact if and only if, for any chain S, a subset of D,

	d <= lub S  =>  there exists s in S such that d <= s.

I.e. you always reach d (or better) after a finite number of steps up the chain.

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

[Jargon File]

Last updated: 1995-01-13

<jargon>

2. Of a design, describes the valuable property that it can all be apprehended at once in one's head. This generally means the thing created from the design can be used with greater facility and fewer errors than an equivalent tool that is not compact. Compactness does not imply triviality or lack of power; for example, C is compact and Fortran is not, but C is more powerful than Fortran. Designs become non-compact through accreting features and cruft that don't merge cleanly into the overall design scheme (thus, some fans of Classic C maintain that ANSI C is no longer compact).

Last updated: 2008-10-13

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Compact COBOL

<language>

A subset of COBOL defined, but not published, ca. 1961.

[Sammet 1969, p. 339].

Last updated: 2008-10-13

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compactCompact COBOLCompact DiscCompact Disc interactive

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Compact Disc

<storage>

(CD) (Not "disk", this spelling is part of the standard).

A 4.72 inch disc developed by Sony and Philips that can store, on the same disc, still and/or moving images in monochrome and/or color; stereo or two separate sound tracks integrated with and/or separate from the images; and digital program and information files.

The same fabrication process is used to make both audio CDs and CD-ROMs for storing computer data, the only difference is in the device used to read the CD (the player or drive).

CD Information Center.

Last updated: 1999-06-23

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Compact Disc interactive

<storage>

(CD-i) An embedded application of CD-ROM allowing the user limited interaction with films, games and educational applications via a special controller.

Last updated: 1994-11-02

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Compact DiscCompact Disc interactiveCompact Disc Read-Only Memory

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Compact Disc Read-Only Memory

<storage>

(CD-ROM) A non-volatile optical data storage medium using the same physical format as audio compact discs, readable by a computer with a CD-ROM drive.

CD-ROM is popular for distribution of large databases, software and especially multimedia applications. The maximum capacity is about 600 megabytes. A CD can store around 640 megabytes of data - about 12 billion bytes per pound weight.

CD-ROM drives are rated with a speed factor relative to music CDs (1x or 1-speed which gives a data transfer rate of 150 kilobytes per second). 12x drives were common in April 1997. Above 12x speed, there are problems with vibration and heat. Constant angular velocity (CAV) drives give speeds up to 20x but due to the nature of CAV the actual throughput increase over 12x is less than 20/12.

20x was thought to be the maximum speed due to mechanical constraints but on 1998-02-24, Samsung Electronics introduced the SCR-3230, a 32x CD-ROM drive which uses a ball bearing system to balance the spinning CD-ROM in the drive to reduce noise.

CD-ROM drives may connect to an IDE interface, a SCSI interface or a propritary interface, of which there are three - Sony, Panasonic, and Mitsumi. Most CD-ROM drives can also play audio CDs.

There are several formats used for CD-ROM data, including Green Book CD-ROM, White Book CD-ROM and Yellow Book CD-ROM. ISO 9660 defines a standard file system, later extended by Joliet.

See also Compact Disc Recordable, Digital Versatile Disc.

Byte, February 1997.

Last updated: 2006-09-25

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Compact Disc Read-Write

Compact Disc Rewritable

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Compact Disc Recordable

<storage>

(CD-R) A write-once version of CD-ROM. CD-Rs can hold about 650 megabytes of data. They are very durable and can be read by normal CD-ROM drives, but once data has been written it cannot be altered.

Standard prerecorded CDs have their information permanently stamped into an aluminium reflecting layer. CD-R discs have a dye-based recording layer and an additional golden reflecting layer.

Digital information is written to the disc by burning (forming) pits in the recording layer in a pattern corresponding to that of a conventional CD.

The laser beam heats the substrate and recording layer to approximately 250 C. The recording layer melts and the substrate expands into the space that becomes available.

Phillips: New Technologies.

See also CD-RW and DVD-RAM.

Last updated: 1999-08-01

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Compact Disc Rewritable

<storage>

(CD-RW) A rewritable version of CD-ROM. A CD-RW drive can write about 650 megabytes of data to CD-RW media an unlimited number of times. Most CD-RW drives can also write once to CD-R media.

CD-RW media cannot be read by CD-ROM drives built prior to 1997 due to the reduced reflectivity (15% compared to 70%) of CD-RW media.

CD-RW drives and media are currently (1999) more expensive than CD-R drives and media. CD-R is sometimes considered a better technology for archival purposes as the data cannot be accidentally modified or tampered with, and encourages better archival practices.

Standard prerecorded CDs have their information permanently stamped into an aluminium reflecting layer. CD-WR discs have a phase-change recording layer and an additional silver (aluminium) reflecting layer.

A laser beam can melt crystals in the recording layer into a non-crystalline amorphous phase or anneal them slowly at a lower temperature back to the crystalline state. The different reflectance of the areas make them appear as the 'pits' and 'lands' of a standard CD.

Phillips: New Technologies.

See also CD-R and DVD-RAM.

Last updated: 1999-08-01

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Compact Disc writer

<storage>

(CD burner) A device that can write data to Compact Disc Recordable (CD-R) or Compact Disc Rewritable (CD-RW) discs. Now both these CD formats are often combined with a DVD writer.

Last updated: 2008-09-16

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Compact Disc RewritableCompact Disc writercompactioncompactness preserving

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compaction

compression

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compactness preserving

<theory>

In domain theory, a function f is compactness preserving if f c is compact whenever c is.

Last updated: 1995-01-13

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compactioncompactness preservingCompaq Computer Corporation

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