Glossary of Acronyms

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HCL - Hardware Compatibility List. The Windows NT Hardware Compatibility List lists the devices supported by Windows NT.

HDA - Head Disk Assembly. The sealed unit of the hard drive.

HDLC - High-Level Data Link Control. A standard protocol developed by the International Standards Organization for software applications and communicating devices operating in synchronous environments. Defines operations at the link level of communications-for example, the format of data frames exchanged between modems over a phone line.

HGC - Hercules Graphics Controller. A monochrome video adapter capable of 720x352 monochrome graphics. The HGC was the first non-IBM video adapter for the IBM PC. See also CGA and MDA.

HMA - High Memory Area. The area of memory which comprises the first 64 KB above the 1 MB boundary. Only available on 80286 CPU's or greater. DOS normally runs in the HMA.

HPFS - High Performance File System. An operating system file system developed by Microsoft for OS/2 1.2 mostly to support the LAN Manager file server. The tables that describe the location of files and freespace are positioned at regular intervals throughout the dataset. New datasets are written where there is a large amount of freespace. This reduces fragmentation and keeps the disk arm from jumping around a large area. HPSF maintains a 512 byte allocation unit no matter now large the volume gets to be.The HPSF directory allows file names to be long, to have multiple periods, and to have lowercase letters. HPSF keeps information in a disk cache area of memory until it needs to be written to a disk.

HSF - Horizontal Scanning Frequency. Measures how fast the monitor can draw a horizontal line across the screen. The display card HSF must match that of the monitor or the circuitry inside the monitor could burn up.

HST - High-Speed Technology. The US Robotics proprietary high-speed modem-signaling scheme, developed as an interim protocol until the V.32 protocol could be implemented in a cost-effective manner. Incorporates trellis-coded modulation for greater immunity from variable phone line conditions, and asymmetrical modulation for more efficient use of the phone channel at speeds of 4800 bps and above. The forward channel transmits at either 9600 bps (older designs) or 14400 bps, and the reverse channel transmits at 450 bps. This technique eliminated the need for the V.32 echo-cancellation hardware that was more costly at the time HST was developed. HST also incorporates MNP-compatible error-control procedures adapted to the asymmetrical modulation.

Hz - Hertz. A unit of frequency equal to one cycle per second, or the distance it takes for light to travel in one second.. One Hz equals one cycle per second. 1 MHz is one million cycles per second wherein one cycle would be the distance it takes for light to travel in one millionth of a second. Typically the Hertz is used to measure the clock speed of the computer. The cycles or clock pattern are the alternating high (5 volts for PC's and 3 volts for laptops) and low (o volts) voltages on a wire.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Compiled by Scott McArdle, MagnaCom Limited. I hope this list has helped you and if there is an item that should be on this list, please let me know. Thanks. PS, I've spent 100's of hours maintaining this list, please don't be a LAMER.