high bit

(Or "high-order bit") The most significant bit in a byte.

See also meta bit, hobbit, dread high bit disease.

[Jargon File]

Last updated: 2012-08-31

High bit-rate Digital Subscriber Line

<communications, protocol>

(HDSL) A form of Digital Subscriber Line, providing T1 or E1 connections over two or three twisted-pair copper lines, respectively. Unlike most other forms of DSL HDSL is not a typical consumer service, it's used mostly to replace traditional T1/E1 connections, such as connecting PBXes to telco offices. The advantage of HDSL over the Alternate Mark Inversion line coding scheme traditionally used on T1/E1 lines is that it requires about an order of magnitude lower bandwidth to carry the same traffic.

Last updated: 1998-05-18

high colour


A colour depth of 16 (or 15) bits per pixel.

Compare true colour.

Last updated: 1999-08-01

High-Definition Multimedia Interface

<video, standard>

(HDMI) an industry standard for connecting digital audio and video devices via a single cable. HDMI can connect any audio/video source, such as a set-top box, DVD player, or A/V receiver to an audio and/or video output device such as a digital television (DTV).

HDMI supports standard, enhanced, or high-definition video, plus multi-channel digital audio. It transmits all ATSC HDTV standards and supports 8-channel, 192kHz, uncompressed digital audio and all currently-available compressed formats (such as Dolby Digital and DTS), HDMI 1.3 adds additional support for new lossless digital audio formats Dolby TrueHD and DTS-HD Master Audio with bandwidth to spare to accommodate future enhancements. HDMI 1.4 incorporates connection via Ethernet.

HDMI was created by Hitachi, Panasonic Corporation, Philips, Sony, Thomson (RCA), Toshiba and Silicon Image and has the support of several major motion picture producers and distributors.


Last updated: 2009-06-29

high density

floppy disk

Higher Education National Software Archive



Last updated: 1995-01-06

higher-order function

<functional programming>

(HOF) A function that can take one or more functions as arguments and/or return a function as its value.

E.g. map in (map f l) which returns the list of results of applying function f to each of the elements of list l.

A curried function is an example of a higher-order function.

Last updated: 2018-05-25

higher-order macro

<functional programming>

A means of expressing certain higher-order functions in a first-order language, proposed by Phil Wadler. Higher-order macros cannot be recursive at the top level but they may contain recursive definitions. For example, the normal, definition of the map function,

 map f []     = []
 map f (x:xs) = f x : map f xs

is higher-order because its argument, f, is a function. The alternative formulation

 map f l = map_f l
 	  map_f []     = []
 	  map_f (x:xs) = f x : m xs

defines a first-order function, map_f, that is a specialisation of map in its first argument. This can be considered a macro because it works purely by textual substitution, requiring no knowledge about f for its validity.

This is an example of partial evaluation - the call, map f l, has been partially evaluated to yeild an intermediate result. This may be useful in optimising compilation or execution, e.g. if the call to f can be subject to in-lining or when executing map_f on a long list.

Last updated: 2018-05-25

High-level Data Link Control


(HDLC) A general-purpose data link control protocol defined by ISO for use on both point-to-point and multipoint (multidrop) data links. It supports full-duplex, transparent-mode operation. It is used extensively in both multipoint and computer networks.

Some manufacturers and other standards bodies still use their own acronyms, e.g. IBM's SDLC (Synchronous Data Link Control), the forerunner of HDLC and ANSI's ADCCP (Advanced Data Communications Control Procedure).

[Fred Halsall, "Data Communications, Computer Networks and Open Systems" 4th edition, 1996, p.237, Addison-Wesley Publishing Co. Reading, Mass., USA].

Last updated: 1997-11-09

high-level language

(HLL) A programming language which provides some level of abstraction above assembly language. These normally use statements consisting of English-like keywords such as "FOR", "PRINT" or "GOTO", where each statement corresponds to several machine language instructions. It is much easier to program in a high-level language than in assembly language though the efficiency of execution depends on how good the compiler or interpreter is at optimising the program.

Rarely, the variants "VHLL" and "MLL" are found.

See also languages of choice, generation.

Last updated: 1994-12-07

high memory area


(HMA) The first 64 kilobytes (minus 16 byte) of the extended memory on an IBM PC. By a strange design glitch the Intel 80x86 processors can actually address 17*64 kbyte minus 16 byte of memory (from 0000:0000 to ffff:ffff) in real mode. In the Intel 8086 and Intel 8088 processors, unable to handle more than 1 megabyte of memory, addressing wrapped around, that is, address ffff:0010 was equivalent to 0000:0000. For compatibility reasons, later processors still wrapped around by default, but this feature could be switched off. Special programs called A20 handlers can control the addressing mode dynamically, thereby allowing programs to load themselves into the 1024--1088 kbyte region and run in real mode. From version 5.0 parts of MS-DOS can be loaded into HMA as well freeing up to 46 kbytes of conventional memory.

Last updated: 1995-01-10

high moby

/hi:' mohb'ee/ The high half of a 512K PDP-10's physical address space; the other half was of course the low moby. This usage has been generalised in a way that has outlasted the PDP-10; for example, at the 1990 Washington D.C. Area Science Fiction Conclave (Disclave), when a miscommunication resulted in two separate wakes being held in commemoration of the shutdown of MIT's last ITS machines, the one on the upper floor was dubbed the "high moby" and the other the "low moby". All parties involved grokked this instantly. See moby.

[Jargon File]

High Performance Computing and Communications

(HPCC) High performance computing includes scientific workstations, supercomputer systems, high speed networks, special purpose and experimental systems, the new generation of large scale parallel systems, and application and systems software with all components well integrated and linked over a high speed network.

["Grand Challenges 1993: High Performance Computing and Communications", Committee on Physical, Mathematical and Engineering Sciences of the Federal Coordinating Council for Science, Engineering and Technology.]

High Performance File System

<file system>

(HPFS) The native file system for IBM's OS/2.

Last updated: 1995-03-06

High Performance Fortran


(HPF) A data parallel language extension to Fortran 90 which provides a portable programming interface for a wide variety of target platforms. The original HPF language specification was produced by the High Performance Fortran Forum, a broad consortium of industry and academia, which met regularly throughout 1992 and early 1993. HPF compilers are now available on most commonly-used computing systems, and users are beginning to gain first hand experience with this language. The Forum has continued to meet in order to address advanced topics.

HPF+ at Vienna.

["High Performance Fortran: Status Report", G.L. Steele Jr <[email protected]>, SIGPLAN Notices 28(1):1-4 (Jan 1993)].

Last updated: 1996-09-09

High Performance Parallel Interface

<hardware, standard>

(HIPPI, previously HPPI) A connection-oriented, point-to-point networking standard using circuit-switching technology at a speed of 800 Mbits/s or 1.6 Gbits/s (simplex or full-duplex). HIPPI is often used for short distances (up to 10km depending on cable type) to connect a supercomputer to routers, frame buffers, mass-storage peripherals and other computers.

HIPPI was developed at Los Alamos National Laboratory and is now ANSI standard X3T9/88-127. Standards for interconnecting with ATM, SONet, and fibre channel are in development.

HIPPI Networking Forum.

Last updated: 1997-06-29

High Performance Routing


(HPR) Routing designed to work in conjunction with APPN Intermediate Session Routing (ISR) network nodes. HPR nodes perform many of the same functions as ISR nodes. For example, HPR nodes use the same method of calculating routes based on the Topology Routing Service database and class of service tables. HPR nodes also supports such APPN features as connection networks and support for parallel transmission groups (TGs). In the HPR architecture, both partner nodes must support HPR for RTP connections to take place between the nodes. If one node supports HPR and the partner node does not, then the link will support ISR functionality only.

["APPN Architecture and Product Implementations Tutorial", IBM, GG24-3669-92].

Last updated: 1997-05-08

High Performance Serial Bus

<hardware, standard>

(Or "IEEE 1394") A 1995 Macintosh/IBM PC serial bus interface standard offering isochronous real-time data transfer.

1394 can transfer data between a computer and its peripherals at 100, 200, or 400 Mbps, with a planed increase to 2 Gbps. Cable length is limited to 4.5 m but up to 16 cables can be daisy-chained yielding a total length of 72 m.

It can daisy-chain together up to 63 peripherals in a tree-like structure (as opposed to SCSI's linear structure). It allows peer-to-peer communication, e.g. between a scanner and a printer, without using system memory or the CPU. It is designed to support plug-and-play and hot swapping.

Its six-wire cable is not only more convenient than SCSI cables but can supply up to 60 watts of power, allowing low-consumption devices to operate without a separate power cord.

Some expensive camcorders included this bus from 1995. It is expected to be used to carry SCSI, with possible application to home automation using repeaters.

Sony calls it I-Link, most people call it "FireWire".

See also Universal Serial Bus, FC-AL.

Last updated: 2014-09-06

High Speed Circuit Switched Data


(HSCSD) A planned feature of GSM Phase 2 defining a standard for circuit switched data transmission over a GSM link at up to 57.6 (78.8?) kbps. This is achieved by concatenating up to four consecutive GSM timeslots, each of which is capable of 14.4 kbit/s. It uses multiplexing and compression or filtering.

The following services toward the fixed network are supported: V.34 up to 28.8 kbps and V.110 with rate adaptation up to 38.4 kbps.

HSCSD is aimed at mobile workstation users. As it is circuit switched, it is suited to streaming applications such as video conferencing and multimedia. Bursty applications like electronic mail, are more suited to packet switched data (as in GPRS).



Last updated: 1999-12-04

High Speed Connect


(HSC) A Hewlett-Packard bus like EISA.

[HP9000 Configuration Guide, January 1996].


Last updated: 1996-06-06

High-speed Net Connect

<hardware, communications>

(HNC) A network interface unit for BS2000 mainframes based on Novell NetWare, supporting Ethernet and FDDI.

Last updated: 2005-02-11

high speed serial interface

<hardware, communications>

(HSSI) A serial port which supports serial transmit speeds of up to 52 megabits per second. It is typically used for leased lines such as DS3 (44.736 Mbps) and E3 (34 Mbps) and for Wide Area Network devices such as routers.

Last updated: 1995-11-20

High Voltage Differential


(HVD) Differential SCSI scheme that has been in use for years. The terminators run on 5 Volts DC.

See also LVD.

Last updated: 1999-02-16

Nearby terms:

Higgs Bugsonhigh bitHigh bit-rate Digital Subscriber Line

Try this search on Wikipedia, OneLook, Google