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`. 9TH EDITION
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`
`Computer Desktop Encyclopedia, Ninth Edition
`
`Copyright© 2001 by The McGraw-Hill Companies. All rights reserved. Printed in the
`United States of America. Except as permitted under the Copyright Act of 1976, no part
`of this publication may be reproduced or distributed in any form or by any means, or
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`1234567890 DOC DOC 901987654321
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`Publisher
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`Page 2 of 7
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`

`

`flat address space
`
`361
`
`flash crowd An unexpected surge in visitors to a Web site, which is
`typically because of some newsworthy event that just took place. It may also
`be due to the announcement of a new service or free software download.
`
`Flash Memory Cards
`
`flash disk A solid state disk made of flash memory chips. Flash
`disks are housed in Type II PC Cards for laptops, but handhelds and
`digital cameras use smaller flash memory cards such as CompactFlash
`and SmartMedia. See flash memory and solid state disk.
`
`flash fusing
`
`See fusing.
`
`flash memory A memory chip that can be rewritten and hold its
`content without power. It is also called a "flash RAM" or "flash ROM"
`chip and is widely used for digital camera film and as storage for many
`consumer and industrial applications. Flash chips replaced earlier ROM
`BIOS chips in a PC so that the BIOS could be updated in place instead
`of being replaced. Flash chips generally have lifespans from lOOK to
`300K write cycles.
`Unlike DRAM and SRAM memory chips, in which a single byte can
`be written, flash memory must be erased and written in fixed blocks,
`typically ranging from 512 bytes up to 256KB. Evolving out of the EEPROM
`chip technology, which can be erased in place, flash memory is less
`expensive and more dense. The term was coined by Toshiba for its ability
`to be erased "in a flash."
`Flash memory chips are conveniently packaged as "flash cards" and
`come in several formats, including the full-size PC Card (ATA PC Card)
`and the smaller CompactFlash, SmartMedia and similar formats.
`There are two types of flash interfaces. The first is the ATA interface,
`which has the same 512-byte block size as the standard hard disk sector. The
`second is the earlier linear flash, which is also used to execute a program
`directly from the chip (XIP). It requires Flash Translation Layer (FTL) or
`Flash File System (FFS) software to make it look like a disk drive. See
`CompactFlash, SmartMedia and Memory Stick. See also Flash.
`
`Flash memory
`cards have
`become very
`popular storage
`devices.
`
`Type II PC
`Cards provide
`auxiliary storage
`for laptops, but
`the
`CompactFlash,
`SmartMedia and
`Memory Stick
`cards are
`expected to
`become the
`digital film of the
`21st century.
`
`The
`Multi Media Card
`is designed for
`the smallest
`handhelds such
`as cellular
`phones and
`pagers.
`
`CompactFlash
`
`Memory Stick
`
`FlashPix A bitmapped-graphics file format that maintains the image
`in several resolutions. It uses more storage space than a comparable TIFF
`file, but when viewed by a Web browser, only the resoultion required for the
`current screen resolution is transmitted, saving download time. FlashPix files use
`the .FPX extension and conform to Microsoft's structured storage format which
`provides multiple "streams" within the file. Descriptive text may also be stored in
`an FPX file that identifies the image and how it was photographed or scanned.
`
`MultiMediaCard
`
`flat address space A memory that is addressed starting with 0. Each
`susequent byte is referenced by the next sequential number (0, 1, 2, 3, etc.) all the
`way to the end of memory. Except for PCs, which are based on the Intel CPU
`architecture, most computers use a flat address space.
`A PC running in 16-bit mode (Real Mode) uses a segmented address space.
`Memory is broken up into 64KB segments, and a segment register always points
`to the base of the segment that is currently being addressed. The PC's 32-bit mode
`is considered a flat address space, but it too uses segments. Since one 32-bit
`segment addresses 4GB, one segment covers all of memory.
`
`Digital Film
`Flash memory cards make the
`perfect digital camera "film." This
`Canon Elph uses CompactFlash.
`
`Computer Desktop Encyclopedia
`
`Page 3 of 7
`
`

`

`..,...
`I
`414 hndler
`--------------------------------------------------------------~--
`' I
`
`(2) A temporary name or number assigned to a file, font or
`other object. For example, an operating system may assign a
`sequential number to each file that it opens as a way of
`identifying it.
`(3) A nickname used when conferencing like a "CB handle"
`used by a truck driver.
`
`handler A software routine that performs a particular task.
`For example, upon detection of an error, an error handler is
`called to recover from the error condition.
`
`Graphics Handles
`The handles are the tiny squares that are
`displayed when you select an object.
`
`handoff Switching a cellular phone transmission from one cell to another as a mobile user moves into a new
`cellular area. The switch takes place in about a quarter of a second so that the caller is generally unaware of it.
`
`handset The part of the telephone that contains the speaker and the microphone. See multihandset cordless.
`
`hands-free computer
`
`See body-worn computer.
`
`handshaking Signals transmitted back and forth over a communications network that establish a valid connection
`between two stations.
`
`hang To have the computer freeze or lock up. When a personal computer hangs, there is often no indication of
`what caused the problem. The computer could have crashed, or it could be something simple such as the printer
`running out of paper.
`
`hanging paragraph Also called "hanging indent,'' it is a paragraph in
`which the first line is set to the left
`margin, but all subsequent lines are
`indented as is this paragraph.
`
`haptic interface Communicating with the computer via some tactile method. Haptic devices sense some form of
`finger, hand, head or body movement.
`
`hard boot
`
`Same as cold boot.
`
`hard coded
`Software that is programmed to get the job done quickly, which means programmed to do a fixed
`number of tasks without regard to future flexibility. It is very easy to do this kind of "brute force programming," and it is
`the ideal kind of programming for one-time jobs. Such programs typically use a fixed set of values and may only work
`with certain types of devices. The problem is that one-time programs often become widely used, even in day-to-day
`operations, but they are difficult to change, because the routines have not been generalized to accept change. Such
`"elegant" programs require much more thought to write, and everybody is in such a hurry that hard-coded, in-elegant
`programs are written a thousand times a day. Hard-coded solutions may run faster, but programming speed is far more
`important than processing speed these days. See data independence.
`
`hard copy
`
`Printed output. Contrast with soft copy.
`
`hard disk The primary computer storage medium, which is made of one or more aluminum or glass platters,
`coated with a ferromagnetic material. Most hard disks are fixed disks, which are permanently sealed in the drive.
`Removable cartridge disks such as !omega's Jaz disks enable the disk to be removed from the computer and used as
`backup or transferred to another machine with the same drive.
`Most desktop hard disks are either IDE (also known as EIDE or ATAPI) or SCSI. The advantage of IDE is their
`lower cost. The advantage of SCSI is that up to seven or more devices can be attached to the same controller board.
`SCSI drives are typically used in high-end servers, because SCSI is available a~ a fault tolerant disk subsystem (RAID
`systems), while IDE drives are found in most desktop and laptop machines. Increasingly, IDE drives are available in
`RAID configurations (see RAID).
`
`Computer Desktop Encyclopedia
`
`Page 4 of 7
`
`

`

`----,.----
`
`(
`415
`hard return
`--1-----------------------------------------------------------------------------11.:
`l
`I
`
`Hard disks provide fast retrieval because they rotate constantly at high speed, from 5,000 to 15,000 rpm. In laptops,
`they can be turned off when idle to preserve battery life.
`Back in the 1950s, the very first hard disks held just a few hundred thousand bytes and used platters 12" in
`diameter. In the 1980s, the first personal computer hard disks started at 5MB (see ST506). Today's hard disks start
`around 20 gigabytes and generally use 3.5" platters for desktop computers and 2.5" platters for notebooks. Smaller
`disks are also used (see Microdrive).
`Hard disks are usually low-level formatted from the factory, which records the original sector identification on
`them. See floppy disk, magnetic disk and format program.
`
`TYPES OF HARD DISKS
`Interface
`Encoding Transfer Rate
`Type
`(Per sec)
`Method*
`
`5 - 160MB
`3 -
`lOOMB
`
`10 - 25MB
`1 -
`3MB
`1 - 4MB
`3 - BMB
`
`Capacities
`
`20MB - 75GB
`SOOMB - BOGB
`
`200MB - 3GB
`BOMB
`- 2GB
`200MB - 2GB
`40MB -
`lGB
`
`Internal Hard Disk
`Hard disks use one or more metal or glass
`platters covered with a magnetic coating.
`
`SCSI***
`EIDE**
`
`IPI
`ESDI
`SMD
`IDE
`
`ST506 RLL
`STS06
`
`RLL
`RLL
`
`RLL
`RLL
`RLL
`RLL
`
`RLL
`MFM
`
`937KB
`625KB
`
`30MB - 200MB
`SMB -
`lOOMB
`
`* Most disks use RLL, but encoding methods are
`not prescribed by all interfaces.
`** For details on EIDE (ATA) modes, see IDE.
`*** For details on SCSI rates, see SCSI.
`
`Hard Disk Measurements Capacity is measured in bytes, and
`speed is measured by transfer rate in bytes per second (see above) and
`access time in milliseconds (ms). Hard disk access times range from 3
`ms to about 15 ms, whereas CDs and DVDs range from 80 ms to 120 ms.
`
`hard disk recorder
`
`See PVR.
`
`hard drive The mechanism that reads and writes a hard disk. The terms
`hard drive and hard disk are used interchangeably.
`
`hard error
`(1) A permanent, unrecoverable error such as a disk read
`error. Contrast with soft error.
`(2) A group of errors that requires user intervention and includes disk read
`errors, disk not ready (no disk in drive) and printer not ready (out of paper).
`
`hard failure
`
`Same as hardware failure.
`
`hard hyphen A hyphen that always prints. Contrast with soft hyphen.
`
`hard macro The design of a logk function that specifies how the
`required logic elements are interconnected and specifies the physical
`pathways and wiring patterns between the components. Also called a
`"macro cell." Contrast with soft macro.
`
`hard return A code inserted into a text document by pressing the ENTER
`key. If the hard return does not display as a symbol on screen, it can usually
`
`First Hard Disk
`Part computer, part tabulator, in 1956, IBM's
`RAMAC was the first machine with a hard
`disk, which was extraordinary technology of
`the times. Each of its 24" diameter platters
`held a whopping 100,000 characters (they
`weren't bytes then) for a total of five million
`characters. (Images courtesy of International
`Business Machines Corporation.
`Unauthorized use not pennitted.)
`
`Computer Desktop Encyclopedia
`
`Page 5 of 7
`
`

`

`910
`
`solenoid
`
`solenoid A magnetic switch that closes a circuit, often used as a relay.
`
`solid ink printer A laser-class printer that uses solid wax inks that are melted into
`a liquid before being used. Instead of jetting the ink onto the paper directly as ink jet
`printers do, solid ink printers jet the ink onto a drum. A better registration of color is
`obtained by transferring the ink to the drum first and then to the printer, because the
`drum can be more tightly controlled than moving paper.
`Tektronix has pioneered the solid ink printer market and is the primary producer of this
`technology. The color print quality of the Tektronix printer is stunning, and its print speed
`generally exceeds that of an equivalent-priced color laser printer, because it prints colors in one
`pass instead of four. With laser printers, each of the four CMYK
`colors must be applied to a secondary accumulator drum one at
`a time before the image is transferred to paper. Tektronix applies
`a four-color solid ink mirror image onto the drum in one pass.
`
`solid logic
`
`Same as solid state.
`
`solid modeling A mathematical technique for
`representing solid objects. Unlike wireframe and surface
`modeling, solid modeling systems ensure that all surfaces
`meet properly and that the object is geometrically correct.
`Solid models allow for interference checking, which tests
`to see if two or more objects occupy the same space.
`Solid modeling is the most complicated of the CAD
`technologies, because it simulates an object internally and
`externally. Solid models can be sectioned (cut open) to reveal
`their internal features, and they can be stress tested as if they
`were physical entities in the real world. See tessellation.
`
`Solid Cross Section
`When an object is built as a
`solid model, cross sections of
`its internal structure can be
`rendered as if it were sliced
`down the middle. This
`two-cycle engine assembly
`was created in MicroStation
`Modeler. (Image courtesy of
`Bentley Systems, Inc.)
`
`solid state An electronic component or circuit made of
`solid materials, such as transistors, chips and bubble memory. There is no mechanical action in a
`solid state device, although an unbelievable amount of electromagnetic action takes place within.
`For data storage, solid state devices are much faster and more reliable than mechanical
`disks and tapes, but are more expensive. Although solid state costs continually drop, disks,
`tapes and optical disks also continue to improve their cost/performance ratio.
`The first solid state device was the "cat's whisker" of the 1930s. A whisker-like wire
`was moved around on a solid crystal in order to detect a radio signal.
`
`solid state disk A disk drive made of memory
`chips used for high-speed data access or in hostile
`environments. Solid state disks are used in battery(cid:173)
`powered, handheld devices as well as in desktop units
`with hundreds of megabytes of storage that contain
`their own UPS systems.
`Different types of storage chips are used for solid
`state disks, both volatile and non-volatile. However a
`solid state disk looks like a standard disk drive to the
`operating system, not a proprietary one that requires
`additional drivers. See flash disk.
`
`solid state laser A laser that uses a glass or
`crystalline laser medium that is excited by light from an
`external source. A solid state laser is not a semiconductor
`laser, although articles may erroneously refer to them as
`such. See laser.
`
`Computer Desktop Encyclopedia
`
`Solid State Disk
`This MegaRam-3000 solid state disk
`system from Imperial Technology
`holds up to 4GB. Access time is
`virtually non existent. In case of power
`failure, the battery enables the unit to
`copy its contents from the memory
`chips to the hard disk. (Image
`courtesy of Imperial Technology, Inc.,
`www.imperialtech.com)
`
`Solid Ink Printhead
`The solid wax ink is melted
`and turned into a liquid
`before it enters the
`plumbing of the printhead.
`The inks are typically jetted
`from the nozzles using the
`piezoelectric drop on
`demand method. The
`printhead in this example is
`as wide as the paper.
`
`Solid State Logic in
`the mid-1960s
`The three transistors in this
`solid state module (top
`removed) used in IBM's
`System/360 computers
`were advanced technology in
`the mid-1960s. (Image
`courtesy of International
`Business Machines
`Corporation. Unauthorized
`use not permitted.)
`
`Page 6 of 7
`
`

`

`SON ET
`
`911
`
`solid state memory Any transistorized, semiconductor or thin film memory that contains no mechanical parts.
`See solid state disk.
`
`solid state relay A relay that contains no mechanical parts. All switching mechanisms are semiconductor or thin
`film components.
`
`soliton A laser pulse that retains its shape in a fiber over long distances. By generating the pulse at a certain frequency
`and at a certain power level, the pulse takes advantage of competing dispersion effects. As it travels, the pulse is lengthened
`and then shortened back to its original size.
`
`solutions The IT buzzword of the twenty-first century. Nobody makes products anymore; everybody just provides
`solutions! See solutions provider.
`
`solutions provider An organization that provides a mix of consulting services, custom programming and hardware
`to solve a customer's information problem. The hardware may be manufactured by the company, purchased from a third
`party or merely recommended. "Solutions" impli~s a range of custom-tailored services rather than only off-the-shelf packages.
`·
`See solutions.
`
`solver Mathematical mechanisms that allow spreadsheets to perform goal seeking.
`
`SOM
`(1) (System Object Model) An object architecture from IBM that provides a full implementation of the CORBA
`standard. SOM is language independent and is supported by a variety of large compiler and application development
`vendors. DSOM, for distributed SOM, allows objects to be used across the network.
`(2) (Self Organizing Map) A two-dimensional map that shows relationships in a neural network..
`
`LAN
`
`0
`
`0 , , ,
`
`, :
`
`· Ethernet ~ayer 2}.· ·
`"
`
`'
`
`,
`
`'
`
`SON ET
`(Synchronous Optical NETwork) A fiber-optic transmission system for high-speed digital traffic. Employed
`by telephone companies and common carriers, SONET speeds range from 51 megabits to multiple gigabits per second.
`SONET is an intelligent system that provides advanced network management and a standard optical interface. It uses
`a self-healing ring architecture that is able to reroute traffic if a line goes down. SONET backbones are widely used to
`aggregate lower-speed Tl and T3 lines.
`SONET is specified in the Broadband ISDN (B-ISDN) standard. The European counterpart is SDH. Following are
`the levels of service. OC (Optical Carrier) refers to the optical signal, and STS (Synchronous Transport Signal) refers to
`the electrical signal, which is the same speed.
`SONET uses time division multiplexing (TDM) to send multiple
`data streams simultaneously. Its smallest increment of provisioniiig
`is VT-1.5, which provides 1.7 Mbps of bandwidth. The next
`increment, STS-1, jumps to 51.84 Mbps. Any data stream that does
`not fill that channel goes wasted.
`Bellcore's GR-2837 standard maps ATM cells onto SONET,
`turning a SONET pipe into a cell-switched (packet-switched)
`transmission carrier that utilizes the full bandwidth of the
`medium without waste.
`SONET is built in a self-healing ring architecture which uses at
`least two transmission paths in the event one fails (see SONET ring).
`
`, ,
`
`',
`
`Copper
`
`WAN
`
`SONET CIRCUITS
`Service
`
`Speed (Mbps)
`1. 7
`VT-1.5
`51.84 (28 DSls or 1 D83)
`STS-1
`OC-1
`155.52 (3 STS-ls)
`STS-3
`OC-3
`155.52 (concatenated)
`OC-3c
`STS-3c
`622.08 (12 STS-1, 4 STS-3)
`STS-12
`OC-12
`622.08 (12 STS-1, 4 STS-3c)
`OC-12c STS-12c
`2488.32 (48 STS-1, 16 STS-3)
`OC-48
`STS-48
`9953.28 (192 STS-1, 64 STS-3)
`OC-192 STS-192
`OC-768 STS-768 39813,12 (768 STS-1, 256 STS-3)
`
`SONET (layer 1)
`
`Fiber
`
`Fiber
`
`Transporting IP
`In a WAN or over the Internet, IP traffic is widely carried
`over SONIT lines, either using ATM as a management
`layer or over SONET directly. In the future, IP is exptected
`to travel directly over DWDM fiber (rightmost diagram).
`
`Computer Desktop Encyclopedia
`
`Page 7 of 7
`
`