An operating system or application program error from which there is no hope of recovery without rebooting ( and thus losing any unsaved work.)
A design method that ensures continued system operation in the event of individual failures by providing redundant elements.
At the component level, designers include redundant chips and circuits and add the capability to bypass faults automatically. At the computer system level, they replicate any elements likely to fail, such as processors and large disk drives.
Fault-tolerant operations often require backup or UPS power systems in the event of a main power failure, and may imply the duplication of entire computer systems in remote locations to protect against vandalism, acts of war, or natural disaster.
A U.S. government regulatory body for radio, television, all interstate telecommunications services, and all international services that originate inside the U.S.
All computer equipment must be certified by the FCC before it can be offered for sale in the U.S. to ensure that it meets the legal limits for conductive and radio frequency emissions, which could otherwise interfere with commercial broadcasts.
Approval by the FCC that a specific computer model meets its standards for radio frequency interference emissions.
There are two levels of certification. Class A certification is for computers used in commercial settings, such as mainframes and minicomputers. Class B certification is for computers used in the home and in home offices, such as PCs,laptops, and portables.
Any cable connector with receptacles designed to receive the pins on the male part of the connector.
A specification for fiber-optic networks transmitting at a speed of up to 100 megabits per second over a dual, counter-rotating, token-ring topology. FDDI is suited to systems that require the transfer of very large amounts of information, such as medical imaging, 3-D seismic processing, oil reservoir simulation, and full-motion video.
fiber optic cable
A transmission technology that sends pulses of light along specially manufactured optical fibers. Each fiber consists of a core, thinner than a human hair, surrounded by a sheath with a much lower refractive index. Light signals introduced at one end of the cable are conducted along the cable as the signals are reflected from the sheath.
Fiber optic cable is lighter and smaller than traditional copper cable, is immune to electrical interference, and has better signal-transmitting qualities. However, it is more expensive than traditional cables and more difficult to repair.
A table maintained by the DOS or OS/2 operating systems that lists all of the clusters available on a disk. The FAT includes the location of each cluster, as well as whether it is in use, available for use, or damaged in soem way and therefore unavailable.
Because files are not necessarily stored in consecutive clusters on a disk, but can be scattered all over the disk, the FAT also keeps track of which pieces belong to which file.
OS/2 supports a compatible version of the DOSFAT, sometimes known as the SuperFAT, which adds 32-bit capabilities to increase speed, access to OS/2 extended attributes, and a free space bitmap which results in much reduced allocation times.
file compression program
An application program that shrinks program or data files, so that they occupy less disk space. The file must then be extracted or decompressed before you can use it.
Many of the most popular file compression programs are shareware, like PKZIP,LHA, and StuffIt for the Macintosh, although utility packages like PC Tools from Central Point Software also contain file compression programs.
The storage of a file in several noncontiguous areas of a disk, rather than as one single unit.
When you store a file on a disk, DOS looks for the first available free cluster on the disk, and stores the file there. If the file is too large for one cluster, the operationg system looks for the next free cluster, and stores the next part of the file there. These clusters may not be next to one another, and may be widely scattered over the disk.
This fragmentation can slow down data retrieval if the problem becomes severe, but by using a defragmenter, you can restore that lost performance. The defragmenter program removes file fragmentation by rewriting all files and directories into contiguous areas of your disk.
The process of recovering deleted or damaged files from a disk. In many operating systems, a deleted file still exists on disk until the space it occupies is overwritten with something else. A file can be deleted accidentally, or can become inaccessible when part of the file's control information is lost.
There are many utility packages that offer file recovery programs (i.e., Norton Utilities for Symantec, PC Tools from Central Point Softwar).
A networked computer used to store files for access by other client computers on the network. On larger networks, the file server may run a special NOS(Network Operating System.
In networking, the sharing of files via the network file server. Shared files can be read, reviewed, and updated by more than one individual. Access to the file or files is often regulated by password protection, account or security clearance, or file locking, to prevent simulataneous changes from being made by more than one person at a time.
A contraction of file specification, commonly used to denote the complete drive letter, path name, directory name, and file name needed to access a specific file.
In an operating system, the structure by which files are organized, stored, and named.
Some file systems are built-in components of the operating system, while others are installable.
(1) Components that provide the basic building blocks for processing data. (2) Under the WDM Stream architecture, also known as a functional device or multimedia processing driver. Each filter's capability is described in part by a number of connection points called pins. Each pin can consume, produce, or both consume and produce a data stream such as digital audio. Specialized tasks can be solved by connecting filters by way of their pins into a topology--for example, to play filtered and mixed audio. (3) Under WDM, a filter is implemented as a kernel-mode entity that is a device object implemented by a kernel driver. (4) Under Microsoft® DirectShow®, a filter is a user-mode entity that is an instance of a COM object, usually implemented by a DLL.
A Unix utility program found on many Internet systems and online services that displays information about a specific user, including full name, login time, and location. Finger may also display the contents of the user's .plan or .project file.
A method of preventing unauthorized access to a computer system, often found on networked computers.
A firewall is designed to provide normal service to authorized users, while at the same time preventing those unauthorized users from gaining access to the system; in reality, they almost always add some level of inconvenience to legal users, and their ability to control illegal access may be questionable.
A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.
There are several types of firewall techniques:
Packet filter: Looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing.
Application gateway: Applies security mechanisms to specific applications, such as FTP and Telnet servers. This is very effective, but can impose a performance degradation.
Circuit-level gateway: Applies security mechanisms when a TCP or UDP connection is established. Once the connection has been made, packets can flow between the hosts without further checking.
Proxy server: Intercepts all messages entering and leaving the network. The proxy server effectively hides the true network addresses.
In practice, many firewalls use two or more of these techniques in concert.
A firewall is considered a first line of defense in protecting private information. For greater security, data can be encrypted.
Any software stored in a form of read-only memory----ROM,EPROM,or EEPROM---that maintains its contents when power is removed. The BIOS used in IBM-compatible computers is firmware.
A method used to process information in which the first item in the list is processed first. FIFO is commonly used when printing a set of documents; the first document received in the queue is the first document to be printed.
A monitor designed to receive an input signal at just one frequency. This is in contrast to a multisynch monitor, which can detect and adjust to a variety of different input signals.
A deliberately insulting e-mail message or post to a USENET newsgroup, usually containing personal attack on the writer of an earlier post.
A prolonged series of flames in a USENET newsgroup, which may have begun as a creative exchange or views but which quickly degenerates into personal attacks and crude name-calling.
flash (disk or drive)
A type of non-volatile memory built into the unit or available as a PC Card that can be plugged into a PCMCIA slot. Flash memory can be written in blocks or over the entire chip, making it easy to erase or update.
A special form of non-volatile EEPROM that can be erased at signal levels normally found inside the PC, so that you can reprogram the contents with whatever you like without pulling the chips out of your computer. Also, once a flash memory has been programmed, you can remove the expansion board it is mounted on and plug it into another computer if you wish.
a calculation of numbers whose decimal point is not fixed but moves or floats to provide the best degree of accuracy. Floating-point calculations can be implemented in software, or they can be performed much faster by a separate floating-point processor.
A special-purpose chip and associated circuitry that directs and controls reading from and writing to a computer's disk drive.
Frequency Modulation is used by entry-level sound cards for sound and music reproduction. Increasingly replaced by Wavetable synthesis.
In an operating system, a process that runs in the foreground is runnign at a higher level of priority than a background task.
Only multitasking operating systems support true foreground and background processing; however, some applications programs can mimic background and foreground processing; many word processors will print a document while still accepting input from the keyboard.
1)To apply the page-layout commands and font specifications to a document and produce the final printed output.
2) The process of initializing a new, blank floppy disk or hard disk so that it can be used to store information.
A feature of online services and bulletin boards that allows subscribers to post messages for others to read, and to reply to messages posted by other users.
A single screen-sized image that can be displayed in sequence with other slightly different images to create animated drawings. A video frame consists of two interlaced fields of either 525 lines (NTSC) or 625 lines (PAL/SECAM), running at 30 frames per second (NTSC) or 25 frames per second (PAL/SECAM). Film runs at 24 frames per second.
An area of memory not currently in use.
A form of software distribution where the author retains copyright of the software, but makes the program available to others at no cost. Freeware is often distributed on bulletin boards, or through user groups. The program may not be resold or distributed by others for profit.
A method of storing digital information on a disk or tape. FM encoding is inefficient in its use of disk space and has largely been replaced by more efficient methods liek modified frequency modulating(MFM) encoding, and the more complex method of run length limited (RLL) encoding and advanced run length limited (ARLL) encoding.
A specialized processor that manipulates data before passing it on to the main processor. In large computer-to-computer communications, a front-end processor is often used to manage all aspects of communications, leaving the main computer free to handle the data processing.
file transfer protocol. In communications, a method of transferring one or more files from one computer to another;often over a modem and a telephone line.
The protocol divides the file into smaller units, and each unit is processed in sequence. The transfer protocol also handles error detection and correction, by one of several methods.The protocol used to access a remote Internet host, and then transfer files between that host and your own computer. Ftp is also the name of the program used to manage this protocol.
Ftp is bade on client/server architecture; you run an ftp client program on your system, and connect with an ftp server running on the Internet host computer. The ftp program originated as a Unix utility, but versions are now available for almost all popular operating systems. The traditional Unix ftp program starts a text-based command processor; modern versions use a graphical user interface with pull-down menus instead. The general consensus seems to be that the graphical versions are easier to use, but once you get the hang of things, the command processor versions, while not as pretty , are usually faster.
In terms of data flow, indicates bidirectional data flow.
Video reproduction at 30 frames per second (NTSC-original signals) or 25 frames per second (PAL-original signals). See also frame.
The set of programmable keys on the keyboard that can perform special tasks assigned by the current application program.
Most keyboards have 10 or 12 function keys, and they are used by an application as shortcut keys.