|
|
 Glossary of Internet and Computer Terms
32-bit/16-bit:
32 bit applications have several advantages over their 16 bit brothers. They
run in their separate address space and they can rarely crash the system. They
are always running in a preemptive multitasking environment and they can have
multiple threads running in parallel. In addition they run generally faster
than their corresponding 16 bit counterparts. 16 bit applications all run in
the same, shared, address space meaning that the crash of a 16 bit application
can easily bring down the entire system. In addition, the 16 bit application
cannot handle long filenames. When you use a 16 bit application you will only
be able to see the 8.3 short filenames.
Access Point:
A hardware device or a computer's software that acts as a communication hub for
users of a wireless device to connect to a wired LAN.
AGP:
Short for Accelerated Graphics Port, a new interface specification developed
by Intel Corporation. AGP is based on PCI, but is designed especially for the
throughput demands of 3-D graphics. Rather than using the PCI bus for graphics
data, AGP introduces a dedicated point-to-point channel so that the graphics
controller can directly access main memory. The AGP channel is 32 bits wide
and runs at 66 MHz. This translates into a total bandwidth of 266 MBps, as opposed
to the PCI bandwidth of 133 MBps. AGP also supports two optional faster modes,
with throughputs of 533 MBps and 1.07 GBps. In addition, AGP allows 3-D textures
to be stored in main memory rather than video memory.
AMD:
(Advanced Microchip Devices) A semiconductor manufacturer and is a major competitor
of Intel. They manufacture the Athlon, Duron, and K6 CPU chips.
Analog:
Anything whose behavior corresponds with the behavior of something else, especially
if the correspondence varies continuously rather than in steps. For example,
the height of the liquid in a thermometer is an analog of the temperature. The
signals that go from a computer to a composite monitor are analog voltages.
AppleTalk:
A protocol suite developed by Apple Computer in the early 1980s, was developed
in conjunction with the Macintosh computer. AppleTalk's purpose was to allow
multiple users to share resources, such as files and printers. The devices that
supply these resources are called servers, while the devices that make use of
these resources (such as a user's Macintosh computer) are referred to as clients.
Hence, AppleTalk is one of the early implementations of a distributed client/server
networking system.
AppleShare:
This is Apple's network system. It is to the Macintosh what FTP is to the PC.
Application:
A software program designed to perform a specific task or group of tasks, such
as word processing, communications, or database management.
ASCII:
It stands for American Standard Code Information Exchange and is pronounced (ask-ee).
A standard code or protocol for displaying characters and transferring data between
computers and associated equipment. It was developed for the purpose of information
exchange among the following:
Associated equipment
Data communications systems
Data processing systems
There are 128 standard ASCII codes each of which can be represented by a 7 digit
binary number: 0000000 through 1111111.
ATA:
Short for Advanced Technology Attachment, a disk drive implementation that integrates
the controller on the disk drive itself. There are several versions of ATA,
all developed by the Small Form Factor (SFF) Committee: ATA: Known also as IDE,
supports one or two hard drives, a 16-bit interface and PIO modes 0, 1 and 2.
ATA-2: Supports faster PIO modes (3 and 4) and multiword DMA modes (1 and 2).
Also supports logical block addressing (LBA) and block transfers. ATA-2 is marketed
as Fast ATA and Enhanced IDE (EIDE).
ATA-3: Minor revision to ATA-2.
Ultra-ATA: Also called Ultra-DMA, ATA-33, and DMA-33, supports multiword DMA
mode 3 running at 33 MBps.
ATA/66: A version of ATA proposed by Quantum Corporation, and supported by Intel,
that doubles ATA's throughput to 66 MBps.
ATA/100: An updated version of ATA/66 that increases data transfer rates to
100 MBps.
ATX:
The modern-day shape and layout of PC motherboards. It improves on the previous
standard, the Baby AT form factor, by rotating the orientation of the board
90 degrees. This allows for a more efficient design, with disk drive cable connectors
nearer to the drive bays and the CPU closer to the power supply and cooling
fan.
AVI:
Stands for Audio/Video Interleaved. AVI is the most common format for audio/video
data on the PC.
Backup:
To copy files to a second medium (a disk or tape) as a precaution in case the
first medium fails. One of the cardinal rules in using computers is. Back up
your files regularly. Even the most reliable computer is apt to break down eventually.
Many professionals recommend that you make two, or even three, backups of all
your files. To be especially safe, you should keep one backup in a different
location from the others. You can back up files using operating system commands,
or you can buy a special-purpose backup utility. Backup programs often compress
the data so that backups require fewer disks. (1) The act of backing up. (2)
A substitute or alternative. The term backup usually refers to a disk or a tape
that contains a copy of data.
Bandwidth:
How much stuff you can send through a connection. Usually measured in bits-per-second.
A full page of English text is about 16,000 bits. A fast modem can move about
57,000 bits in one second. Full-motion full-screen video would require roughly
10,000,000 bits-per-second, depending on compression.
Baud:
Pronounced bawd. The term is named after J.M.E. Baudot, the inventor of the
Baudot telegraph code. In common usage the baud rate of a modem is how many
bits it can send or receive per second. Technically, baud is the number of times
per second that the carrier signal shifts value - for example a 1200 bit-per-second
modem actually runs at 300 baud, but it moves 4 bits per baud (4 x 300= 1200
bits per second).
BIOS:
Stands for Basic Input/Output System. The BIOS gives the computer a little built-in
starter kit to run the rest of softwares from floppy disks (FDD) and hard disks
(HDD). The BIOS is responsible for booting the computer by providing a basic
set of instructions.
Binary:
This is a basic system of numbering using ones and zeros.
Bit:
(Binary DigIT) A single digit number in base-2, in other words, either a 1 or
a zero. The smallest unit of computerized data. Bandwidth is usually measured
in bits-per-second.
Blog:
(Slang term for a Weblog) This is a publicly accessible personal journal for
an individual. Similar to a personal diary, but shared over the web. The activity
of updating a blog is "blogging" and someone who keeps a blog is a
"blogger." Blogs are typically updated daily using software that allows
people with little or no technical background to update and maintain the blog.
Postings on a blog are almost always arranged in chronological order with the
most recent additions featured most prominently.
Bluetooth:
Radio technology that connects electronic devices without using a cable. Data
and voice can be exchanged at ranges of up to 10 meters without the need for
devices to be lined up together.
BMP:
(pronounced "bimp"): It's a bitmap, an image made up of little dots.
BNC:
Different sources expand BNC as Bayonet Navy Connector, British Naval Connector,
Bayonet Neill Concelman or Bayonet Nut Connection. A connector widely used in
the CCTV industry, usually for coaxial cable. Easy to install and reliable with
little video signal loss. Pictures of BNC Connectors
Boot Disk:
A diskette from which you can boot your computer. Normally, your computer boots
from a hard disk, but if the hard disk is damaged (for example, by a virus),
you can boot the computer from a bootable diskette. For this reason, it's a
good idea to make sure you always have a bootable diskette on hand. In Windows
95, you can create a bootable diskette by following these steps: 1. Insert a
blank, formatted diskette in the floppy drive 2. Select Start->Settings->Control
Panel 3. Open Add/Remove Programs 4. Select the Startup Disk tab and press the
Create Disk... button A bootable diskette is also called a bootable floppy,
boot disk, and startup disk.
Buffer:
A place, especially in RAM, for the temporary storage of data for the purpose
of speeding up an operation such as printing or disk access. Data from a buffer
is available more quickly than data from where the buffer got it. Typically
buffers get data before it is needed so it will be ready quickly when it is
needed. Similar to cache.
Browser:
A browser is the software used for viewing pages on the web. Two examples are
Microsoft Internet Explorer and Netscape Navigator.
BUS:
A collection of wires through which data is Transmitted from one part of a computer
to another. You can think of a bus as a highway on which data Travels within
a computer. When used reference to Personal computers, the term bus usually
refers to Internal bus. This is a bus that connects all the internal computer
components to the CPU and main memory. There's also an expansion bus that enables
expansion boards to access the CPU and memory. All buses consist of two parts
-- an address bus and a data bus. The data bus transfers actual data whereas
the address bus transfers information about where the data should go. The size
of a bus, known as its width, is important because it determines how much data
can be transmitted at one time. For example, a 16-bit bus can transmit 16 bits
of data, whereas a 32-bit bus can transmit 32 bits of data. Every bus has a
clock speed measured in MHz. A fast bus allows data to be transferred faster,
which makes applications run faster. On PCs, the old ISA bus is being replaced
by faster buses such as PCI. Nearly all PCs made today include a local bus for
data that requires especially fast transfer speeds, such as video data. The
local bus is a high-speed pathway that connects directly to the processor. In
networking, a bus is a central cable that connects all devices on a local-area
network (LAN). It is also called the backbone.
Bus Mastering:
Refers to a feature supported by some bus architectures that enables a controller
connected to the bus to communicate directly with other devices on the bus without
going through the CPU. Most modern bus architectures, including PCI, support
bus mastering because it improves performance.
Byte:
Unit of memory or data needed to represent one character in binary (1s and 0s)
form. One byte is usually 8 bits.
Cable modem (CM):
Client device for providing data over a cable TV network.
Cache:
A special block of fast memory used for temporary storage of data for quick
retrieval. Compare buffer. (Think of a buffer as a temporary holding place between
two devices, and a cache as a temporary holding place for one device.)
Cache RAM:
Cache (usually SRAM) stores frequently requested data and instructions. It is
a small block of high-speed memory located between the CPU and the main memory.
When your computer processor needs data, it will check the Cache first to see
if it is there. If the data is not there, it will retrieve it from the slower
main memory.
CATV:
Community Antenna Television or Cable TV system. Can be all coaxial or HFC (Hybrid
Fiber Coax) based.
CD-ROM:
(Compact Disc Read-Only Memory) An optical storage medium that can hold about
600 MB of data and is accessed with lasers.
CGA:
Stands for Color Graphics Adapter. IBM's first microcomputer color standard.
CGA allowed a maximum of four colors at a resolution of 320 x 200 or two colors
at 640 x 200.
CGI:
The Common Gateway Interface. A standard for running external programs from
a World-Wide Web HTTP server. What is returned from the CGI program is based
on what was requested, and this information can be accessed and returned to
the user in many different ways.
Channel:
A specific frequency and bandwidth combination. Used in this context about TV
channels for television services and downstream data for cable modems.
Chassis:
The physical framework of the computer system that houses modules, wiring, and
power supplies.
Client:
Between slave and peer. A system that is able to operate independently, but
has some degree of dependence on another system. Frequently refers to computers
on a local area network. Compare peer, slave.
Clock Speed:
The clock speed is the frequency which determines how fast devices that are
connected to the system bus operate. The speed is measured in millions of cycles
per second (MHz or megahertz) and is generated by a quartz crystal on the motherboard
which acts as a kind of metronome. Devices that are synchronized with the clock
may run faster or slower but their speed is determined by multiplying or dividing
a factor by the clock speed.
Clustering:
A technique in which two or more servers are interconnected and can access a
common storage pool. Clustering prevents the failure of a single file server
from denying access to data and adds computing power to the network for large
numbers of users.
CMOS:
Abbreviation of complementary metal oxide semiconductor. Pronounced see-moss,
CMOS is a widely used type of semiconductor. CMOS semiconductors use both NMOS
(negative polarity) and PMOS (positive polarity) circuits. Since only one of
the circuit types is on at any given time, CMOS chips require less power than
chips using just one type of transistor. This makes them particularly attractive
for use in battery-powered devices, such as portable computers. Personal computers
also contain a small amount of battery-powered CMOS memory to hold the date,
time, and system setup parameters.
COBOL:
Stands for Common Business Oriented Language. A computer programming language
invented during the second generation of computers and designed to meet the
needs of business. Although less often used today, it was well-suited for writing
programs that process large files and generate reports.
Codec:
1. Short for compressor/decompressor, a codec is any technology for compressing
and decompressing data. Codecs can be implemented in software, hardware, or
a combination of both. Some popular codecs for computer video include MPEG,
Indeo and Cinepak. 2. In telecommunications, (short for coder/decoder) a device
that encodes or decodes a signal. For example, telephone companies use codecs
to convert binary signals transmitted on their digital networks to analog signals
converted on their analog networks. 3. The translation of a binary value into
a voltage that can be transmitted over a wire.
Collision:
The situation that occurs when two or more devices attempt to send a signal
along the same channel at the same time. The result of a collision is generally
a garbled message. All computer networks require some sort of mechanism to either
prevent collisions altogether or to recover from collisions when they do occur.
COM:
Stands for Component Object Module. In DOS systems, the name of a serial communications
port. DOS supports four serial ports: COM1, COM2, COM3, and COM4. However, most
software uses system interrupts to access the serial ports, and there are only
two IRQ lines reserved. This means that the four COM ports share the same two
IRQ lines. Typically, COM1 and COM3 use IRQ4, while COM2 and COM4 use IRQ3.
So in general, if you have two devices, one of which is attached to COM1 and
the other to COM3, you cannot use them simultaneously.
Command Line:
Commands you type to run an application. You can type commands at an MS-DOS
prompt or in the Run dialog box in the Program Manager of Windows. Interfaces
in which you type commands rather than choose them from a menu are often called
command line interfaces. MS-DOS has a command line interface while the Macintosh
does not.
Config.SYS:
The configuration file for DOS systems. Whenever a DOS computer boots up, it
reads the CONFIG.SYS file (if it exists) and executes any commands in it. The
most common commands are BUFFERS= and FILES=, which enable you to specify the
buffer size and the number of files that can be open simultaneously. In addition,
you can enter commands that install drivers for devices.
Controller:
A device that controls the transfer of data from a computer to a peripheral
device and vice versa. For example, disk drives, display screens, keyboards,
and printers all require controllers. In personal computers, the controllers
are often single chips. When you purchase a computer, it comes with all the
necessary controllers for standard components, such as the display screen, keyboard,
and disk drives. If you attach additional devices, however, you may need to
insert new controllers that come on expansion boards. Controllers must be designed
to communicate with the computer's expansion bus. There are three standard bus
architectures for PCs -- the AT bus, PCI (Peripheral Component Interconnect),
and SCSI. When you purchase a controller, therefore, you must ensure that it
conforms to the bus architecture that your computer uses.
Conventional Memory:
On DOS systems, conventional memory refers to the portion of memory that is
available to standard DOS programs. DOS systems have an address space of 1MB
(megabyte), but the top 384K (called high memory) is reserved for system use.
This leaves 640K of conventional memory. Everything above 1MB is either extended
or expanded memory.
CPU:
Central Processing Unit. In a microcomputer, a processor on an IC chip (called
a microprocessor) that serves as the heart of the computer. It interprets and
carries out instructions, performs numeric computations, and controls the peripherals
connected to it. Often the entire system unit is called the CPU.
Cyberspace:
Author William Gibson in his novel Neuromancer describes a more highly developed
form of the Internet and who originally coined the term Cyberspace. The word
Cyberspace is currently used to describe the whole range of information resources
available through computer networks.
Daisy Chain:
A hardware configuration in which devices are connected one to another in a
series. The SCSI interface , for example, supports a daisy chain of up to 7
devices.
Data:
Anything that is recorded or used for processing. The stuff that transfers between
computers needed a name -- data seemed good.
Data Bus:
A group of parallel conductors (circuit traces) found on the motherboard that
is used by the CPU to send and receive data from all the devices in the computer.
Also called the external data bus.
Data Conversion:
The translation of data from one format to another. Often when data are moved
from one system to another, some form of data conversion is required to convert
the data to a format the receiving system can interpret. Sometimes it is necessary
to have an intermediate format.
Database:
Anything that accepts data is a database. A pile of newspapers is a database.
A computer database has the ability to manipulate that data. It is possible
to attach applications to that database to search the contents.
Data Rate:
Speed that information moves from one item to another. This is usually in the
form of bits.
DDR:
Stands for "Double Data Rate." It is an advanced version of SDRAM,
a type of computer memory. DDR-SDRAM, sometimes called "SDRAM II,"
can transfer data twice as fast as regular SDRAM chips. This is because DDR
memory can send and receive signals twice per clock cycle. The efficient operation
of DDR-SDRAM makes the memory great for notebook computers since it uses up
less power.
DDS:
Stands for Direct Digital Signal. A network whose infrastructure equipment is
completely digital. All signals on such a network are transmitted digitally
and there is no need for analog-to-digital converters.
Decoder:
A circuit or device that restores a coded signal to its original form based
on knowledge of the process used to code the signal.
Decryption:
Decryption is the process of converting encrypted data back into its original
form, so it can be understood.
Dedicated Line:
This is a phone line meant specifically for one thing, like being attached to
a computer.
Delimiter:
A text character that marks the beginning and/or end of a unit of data or separates
different data components. For example, periods are used as delimiters in domain
names, hyphens and parentheses are used in phone numbers and social security
numbers, and blank spaces and commas are used in written text. In HTML the opening
delimiter of an element or tag is the less than symbol, <, and the closing
delimiter is greater than symbol, >.
Demodulation:
This is the process of converting analog information (like over phone lines)
into digital information (like in a computer). See "Modem" for more.
Dial-Up Line:
This is a telephone line that is connected to a server. When it is called, tones
are exchanged between the server and the devise calling in order to attach.
Dial-Up Networking:
A component in Windows 95 that enables you to connect your computer to a network
via a modem. If your computer is not connected to a LAN and you want to connect
to the Internet, you need to configure Dial-Up Networking (DUN) to dial a Point
of Presence (POP) and log into your Internet Service Provider (ISP). Your ISP
will need to provide certain information, such as the gateway address and your
computer's IP address. You access DUN through the My Computer icon. You can
configure a different profile (called a connectoid) for each different online
service you use. Once configured, you can copy a connectoid shortcut to your
desktop so that all you need to do to make a connection is double-click the
connectoid icon.
Digital:
A system that defines data in a discrete, non-fluctuating (i.e., non-analogue),
numerical method. Similar to a binary system.
DIMM:
Short for dual in-line memory module, a small circuit board that holds memory
chips. A single in-line memory module (SIMM) has a 32-bit path to the memory
chips whereas a DIMM has 64-bit path. Because the Pentium processor requires
a 64-bit path to memory, you need to install SIMMs two at a time. With DIMMs,
you can install memory one DIMM at a time.
Direct X:
A set of APIs developed by Microsoft that enables programmers to write programs
that access hardware features of a computer without knowing exactly what hardware
will be installed on the machine where the program eventually runs. DirectX
achieves this by creating an intermediate layer that translates generic hardware
commands into specific commands for particular pieces of hardware. In particular,
DirectX lets multimedia applications take advantage of hardware acceleration
features supported by graphics accelerators. DirectX 2, released in 1996, supports
the Direct3D architecture. DirectX 5, released in 1998, adds new layers to the
DirectX API. In addition to the low-level layer that communicates directly with
multimedia hardware, DirectX 5 also includes a Media layer that enables programmers
to manipulate multimedia objects and streams. DirectX 5 also supports USB and
IEEE 1394 buses, AGP, and MMX.
DMA:
Hardware devices attached to PCs (ranging from keyboards to sound cards) can
be designed to send their instructions to and from main memory in one of two
ways. The default is to ask the CPU to do the work. The more efficient way is
to allocate one of the PC's DMA channels to send instructions directly to memory.
This leaves the CPU free to do more important things. Like IRQs, DMA channels
are limited in number, and you can't allocate one channel to more than one device
(unless you want to grind your system to a halt). Most users come in contact
with DMA when they install a sound card that--if they're lucky--picks the right
channel during setup.
DNS:
Domain Name Service, is the system used on the Internet for mapping names (called
domain names) to the actual numerical addresses of machines on the Internet
(IP addresses). Every computer on the Internet has its own number. Since humans
can remember names more easily, DNS maps the numbers, such as 906.87.42.119,
to names, such as www.5starsupport.com. When you type a Web page address into
your browser, your computer consults a DNS server to find the actual numerical
address for the machine that goes by that name.
DOS:
Stands for Disc Operating System. It is a generic term for the many programs
that accept commands to trip applications to run. The most popular is MS-DOS
(MS stands for Microsoft).
Downstream:
The data flowing from the Cable Modem Termination System to the cable modem.
Downstream frequency:
The frequency used for transmitting data from the Cable Modem Termination System
to the cable modem. Normally in the 42/65-850 MHz range depending on the actual
cable plant capabilities.
Domain:
A group of computers and devices on a network that are administered as a unit
with common rules and procedures. Within the Internet, domains are defined by
the IP address. All devices sharing a common part of the IP address are said
to be in the same domain.
Domain Name:
A name that identifies one or more IP addresses. Every domain name has a suffix
that indicates which top-level (TLD) domain it belongs to. There are only a
limited number of such domains. For example:
gov - Government agencies
edu - Educational institutions
org - Organizations (nonprofit)
mil - Military
com - commercial business
net - Network organizations
ca - Canada
th - Thailand
Because the Internet is based on IP addresses, not domain names, every Web server
requires a Domain Name System (DNS) server to translate domain names into IP
addresses.
DPI:
Stands for Dots Per Inch.
DRAM:
DRAM (dynamic random access memory) is most commonly used type of memory in
computers. A bank of DRAM memory usually forms the computer's main memory. It
is called Dynamic because it needs to be refreshed.
Driver:
A program that controls a device. Every device, whether it be a printer, disk
drive, or keyboard, must have a driver program. Many drivers, such as the keyboard
driver, come with the operating system. For other devices, you may need to load
a new driver when you connect the device to your computer. In DOS systems, drivers
are files with a .SYS extension. In Windows environments, drivers often have
a .DRV extension. A driver acts like a translator between the device and programs
that use the device. Each device has its own set of specialized commands that
only its driver knows. In contrast, most programs access devices by using generic
commands. The driver, therefore, accepts generic commands from a program and
then translates them into specialized commands for the device.
DSP: (Digital Signal Processor)
DSP chips are widely used in sound cards, fax machines, modems, cellular phones,
high-capacity hard disks and digital TVs. The first DSP chip used in a commercial
product was believed to be from Texas Instruments, which was used in its very
popular Speak & Spell game in the late 1970s. DSP chips are used in sound
cards for recording and playback and speech synthesis. Other audio uses are
amplifiers that simulate concert halls and surround-sound effects for music
and home theater.
DTP:
Desk Top Publisher(ing) - A PC Term that describes a program that enables you
to design, create and print a variety of projects such as letterheads, birthday
cards, calendars, business cards, invitations etc. that would have previously
only been possible by using the services of an outside printers business.
Dumb Terminal:
This a video screen that is seeing manipulation in another computer. Example:
If you log in to AOL, your computer is not doing the work -- AOL's computer
is. You are just being offered a window into that world. That window is your
screen. It's a terminal, but it's just watching -- thus a dumb terminal.
DVD:
Short for digital versatile disc or digital video disc, a new type of CD-ROM
that holds a minimum of 4.7GB (gigabytes), enough for a full-length movie. Many
experts believe that DVD disks, called DVD-ROMs, will eventually replace CD-ROMs,
as well as VHS video cassettes and laser discs. The DVD specification supports
disks with capacities of from 4.7GB to 17GB and access rates of 600 KBps to
1.3 MBps. One of the best features of DVD drives is that they are backward-compatible
with CD-ROMs. This means that DVD players can play old CD-ROMs, CD-I disks,
and video CDs, as well as new DVD-ROMs. Newer DVD players, called second-generation
or DVD-2 drives, can also read CD-R and CD-RW disks. DVD uses MPEG-2 to compress
video data.
Dynamic URL:
A URL that results from the search of a database-driven Web site or the URL
of a Web site that runs a script. In contrast to static URLs, in which the contents
of the Web page do not change unless the changes are coded into the HTML, dynamic
URLs are generated from specific queries to a site's database. The page is merely
a template to display the results of the query. Most of the content comes from
the database that is associated with the site. Instead of changing information
in the HTML code, the data is changed in the database.
EIDE:
(Enhanced Integrated Drive Electronics), also called EIDE, is a term that Western
Digital coined in 1994 to represent a particular set of extensions it devised
to the original AT Attachment standard. At that time, the official ATA standard
was rather limiting, and work was progressing towards the new ATA-2 standard.
Western Digital decided that it did not want to wait for the new standard, and
also that it could better position itself as a market leader by creating a new
feature set for (then) future drives. The name "Enhanced IDE" was
presumably selected to build upon the common name for ATA then in popular use:
IDE.
E-Mail:
Stands for Electronic Mail. This is a system of relaying messages across the
Internet, from one Internet user to another.
Emulation:
Refers to the ability of a program or device to imitate another program or device.
Many printers, for example, are designed to emulate Hewlett-Packard LaserJet
printers because so much software is written for HP printers. By emulating an
HP printer, a printer can work with any software written for a real HP printer.
Emulation tricks the software into believing that a device is really some other
device. Communications software packages often include terminal emulation drivers.
This enables your PC to emulate a particular type of terminal so that you can
log on to a mainframe. It is also possible for a computer to emulate another
type of computer. For example, there are programs that enable an Apple Macintosh
to emulate a PC.
Encryption:
Encryption is the process of converting data into "unreadable code"
is so that unauthorized people cannot understand the content. Encryption may
be used to make stored data private (e.g., data that is stored on a potentially
vulnerable hard disk), or to allow a nonsecure communications channel to serve
as a private communications channel. Encryption is sometimes described as the
process of converting plaintext into ciphertext. To decipher the message, the
receiver of the encrypted data must have the proper decryption key.
EPROM:
Acronym for erasable programmable read-only memory, and pronounced ee-prom,
EPROM is a special type of memory that retains its contents until it is exposed
to ultraviolet light. The ultraviolet light clears its contents, making it possible
to reprogram the memory. To write to and erase an EPROM, you need a special
device called a PROM programmer or PROM burner. An EPROM differs from a PROM
in that a PROM can be written to only once and cannot be erased. EPROMs are
used widely in personal computers because they enable the manufacturer to change
the contents of the PROM before the computer is actually shipped. This means
that bugs can be removed and new versions installed shortly before delivery.
ESD:
Stands for Electro Static Discharge and is defined as a sudden flow of electricity
between two objects at different electrical potentials. ESD is a primary cause
of integrated circuit damage or failure. ESD Testing:
One kind of test that hardware usually has to pass to prove it is suitable for
sale and use. The hardware must still work after is has been subjected to some
level of electrostatic discharge. Some organizations have their own ESD requirements
which hardware must meet before it will be considered for purchase.
Different countries have different legal regulations about levels of ESD.
How to help prevent ESD:
The best way to help prevent ESD is either to use a wrist strap, or a grounding
mat. However most users do not have access to such items therefore you can follow
the below guidelines to help prevent ESD as much as possible. Clothes - Insure
what you are not wearing an item that conducts a lot of Electrical Charge, such
as a wool sweater. Also it is generally a good idea to remove all jewelry as
well.
Weather - When working on your computer insure there is not an electrical storm
outside which increases the potential of ESD.
Cords - Insure everything is removed from the back of the computer (power cord,
mouse, keyboard, etc).
Zero Potential - Insure you and the computer are at Zero Potential by continuously
touching the un-painted metal chassis (computer frame) or the Power supply.
Standing - When working inside the computer it is highly recommended that you
stand at ALL times.
Surface - It is always best to stand on a wooden surface. Avoid working on a
computer in carpeted areas.
Ethernet:
A networking system that enables high speed data communication over coaxial
cables. The Ethernet network system supports TCP/IP, AppleTalk, Novell Netware,
and other network protocols. An Ethernet (LAN) connection is 10 Mbit/s or 100
Mbit/s, and is used to connect many computers that can all "talk"
directly to each other. Normally they will all talk with a few servers and printers,
but the network is all-to-all. The distance is normally limited to below 1 km.
Expanded Memory:
Also known as EMS (Expanded Memory Specification), expanded memory is a technique
for utilizing more than 1MB (megabyte) of main memory in DOS -based computers.
The limit of 1MB is built into the DOS operating system. The upper 384K is reserved
for special purposes, leaving just 640K of conventional memory for programs.
Expansion Bus:
A group of control lines that provide a buffered interface to devices located
either on the system board or on cards that are plugged into expansion connectors.
Common expansion buses included on the system board are USB, PC Card, and PCI.
Extended Memory:
Memory above and beyond the standard 1MB (megabyte) of main memory that DOS
supports. Extended memory is only available in PCs with an Intel 80286 or later
microprocessor. Two types of memory can be added to a PC to increase memory
beyond 1MB: expanded memory and extended memory. Expanded memory conforms to
a published standard called EMS that enables DOS programs to take advantage
of it. Extended memory, on the other hand, is not configured in any special
manner and is therefore unavailable to most DOS programs. However, MS-Windows
and OS/2 can use extended memory.
External Modem:
A modem that resides in a self-contained box outside the computer system. Contrast
with an internal modem, which resides on a printed circuit board inserted into
the computer. External modems tend to be slightly more expensive than internal
modems. Many experts consider them superior because they contain lights that
indicate how the modem is functioning. In addition, they can easily be moved
from one computer to another. However, they do use up one COM port.
Extranet:
An extranet is a private network that uses the Internet protocols and the public
tele-communication system to share a business’s information , data or operations
with external suppliers, vendors or customers. An extranet can be viewed as
the external part of a company’s Intranet. See Also: Intranet
FAT:
Stands for File Allocation Table. Basically this is a table of contents in a
directory that tells the computer what all is in there. Look at your Netscape
cache, you'll see a FAT. It'll be the first file.
FAT 32:
A new version of the file allocation table (FAT) available in Windows 95 OSR
2 and Windows 98. FAT32 increases the number of bits used to address clusters
and also reduces the size of each cluster. The result is that it can support
larger disks (up to 2 terabytes) and better storage efficiency (less slack space).
Fax Modem:
A device you can attach to a personal computer that enables you to transmit
and receive electronic documents as faxes. A fax modem is like a regular modem
except that it is designed to transmit documents to a fax machine or to another
fax modem. Some, but not all, fax modems do double duty as regular modems. As
with regular modems, fax modems can be either internal or external. Internal
fax modems are often called fax boards.
FDDI:
Fiber Distributed Data Interface -- A standard for transmitting data on optical
fiber cables at a rate of around 100,000,000 bits-per-second (10 times as fast
as Ethernet, about twice as fast as T-3).
Fiber Optic:
An alternative to copper wire for transmitting information. In fiber optics,
pulses of light representing binary data are flashed along a flexible glass
fiber. The advantage over copper wiring is that a single strand of optical fiber
can carry thousands and thousands of different frequencies at once without data
loss.
File Sharing:
This is the most important feature of the Internet. This is a method of allowing
one server to give the same file to many different end users.
Firmware:
Software (programs or data) that has been written onto read-only memory (ROM).
Firmware is a combination of software and hardware. ROMs, PROMs and EPROMs that
have data or programs recorded on them are firmware.
FSB:
Stands for Front Side Bus, which denotes the speed at which your processor interacts
with the components on the motherboard. Typically the FSB is 100Mhz or 133Mhz,
but overclockers often manipulate this value to increase the speed at which
their processor runs. i.e. 100Mhz FSB X 5.0 clock multiplier = 500Mhz processor.
FTP:
Stands for File Transfer Protocol.
Full Duplex:
Refers to the transmission of data in two directions simultaneously. For example,
a telephone is a full-duplex device because both parties can talk at once. In
contrast, a walkie-talkie is a half-duplex device because only one party can
transmit at a time. Most modems have a switch that lets you choose between full-duplex
and half-duplex modes. The choice depends on which communications program you
are running. In full-duplex mode, data you transmit does not appear on your
screen until it has been received and sent back by the other party. This enables
you to validate that the data has been accurately transmitted. If your display
screen shows two of each character, it probably means that your modem is set
to half-duplex mode when it should be in full-duplex mode.
Gateway:
As in Common Gateway Interface (CGI). It is a piece of software that allows
two items to communicate with each other. They are used to make connections
between computers and systems inside that computer.
Gigabyte:
2 to the 30th power (1,073,741,824) bytes. One gigabyte is equal to 1,024 megabytes.
Gigabyte is often abbreviated as G or GB.
GUI - Graphical User Interface:
A program interface that takes advantage of the computer's graphics capabilities
to make the program easier to use. Well-designed graphical user interfaces can
free the user from learning complex command languages. On the other hand, many
users find that they work more effectively with a command-driven interface,
especially if they already know the command language.
Half-Duplex:
Refers to the transmission of data in just one direction at a time. For example,
a walkie-talkie is a half-duplex device because only one party can talk at a
time. In contrast, a telephone is a full-duplex device because both parties
can talk simultaneously. Most modems contain a switch that lets you select between
half-duplex and full-duplex modes. The correct choice depends on which program
you are using to transmit data through the modem. In half-duplex mode, each
character transmitted is immediately displayed on your screen. (For this reason,
it is sometimes called local echo -- characters are echoed by the local device).
In full-duplex mode, transmitted data is not displayed on your monitor until
it has been received and returned (remotely echoed) by the other device. If
you are running a communications program and every character appears twice,
it probably means that your modem is in half-duplex mode when it should be in
full-duplex mode, and every character is being both locally and remotely echoed.
Handshaking:
The process by which two devices initiate communications. Handshaking begins
when one device sends a message to another device indicating that it wants to
establish a communications channel. The two devices then send several messages
back and forth that enable them to agree on a communications protocol.
Hardware:
These are the physical items including your computer and floppy discs.
Headend:
Central distribution point for a CATV system. Video signals are received here
from satellites and maybe other sources, frequency converted to the appropriate
channels, combined with locally originated signals, and rebroadcast onto the
HFC plant. The headend is where the CMTS is normally located.
Heat Sink:
A component designed to lower the temperature of an electronic device by dissipating
heat into the surrounding air. All modern CPUs require a heat sink. Some also
require a fan. A heat sink without a fan is called a passive heat sink; a heat
sink with a fan is called an active heat sink. Heat sinks are generally made
of a zinc alloy and often have fins.
HST:
High Speed Technology- Before the invention of the CCITT V.32 modem standards
for 9600 BPS modems, US Robotics invented a proprietary protocol that runs even
faster at 14,400 BPS. It became popular on US bulletin board system, but never
caught on outside the USA. It is gradually being replaced by V.32.
Host:
A computer on a network that provides services to other computers on the network.
Unless you have your own server, you need a hosting company who provides a server
or computer that is connected to the internet and makes your web pages available
to the rest of the internet.
HTML:
Hyper Text Markup Language. It is a collection of structuring and formatting
tags used to create Web pages.
HTTP:
Stands for HyperText Transport Protocol. Common protocol used to communicate
between World Wide Web Servers.
Hub:
A common connection point for devices in a network. Hubs are commonly used to
connect segments of a LAN. A hub contains multiple ports. When a packet arrives
at one port, it is copied to the other ports so that all segments of the LAN
can see all packets. A passive hub serves simply as a conduit for the data,
enabling it to go from one device (or segment) to another. So-called intelligent
hubs include additional features that enables an administrator to monitor the
traffic passing through the hub and to configure each port in the hub. Intelligent
hubs are also called manageable hubs. A third type of hub, called a switching
hub, actually reads the destination address of each packet and then forwards
the packet to the correct port.
Hypertext:
This is a mark-up language that allows for non-linear transfers of data. The
method allows your computer to provide the computational power rather than attaching
to a mainframe and waiting for it to do the work for you.
ICMP:
(Internet Control Message Protocol) A message control and error-reporting protocol
between a host server and a gateway to the Internet. ICMP uses Internet Protocol
(IP) datagrams, but the messages are processed by the IP software and are not
directly apparent to the application user.
Icon:
A small video display that acts as an activation link when clicked on.
IDE:
(Integrated Development Environment) A programming environment integrated into
an application. For example, Microsoft Office applications support various versions
of the BASIC programming language. You can develop a WordBasic application while
running Microsoft Word.
IMAP:
Internet Message Access Protocol
IMAP is gradually replacing POP as the main protocol used by email clients in
communicating with email servers.
Using IMAP, an email client program can not only retrieve email but can also
manipulate messages stored on the server without having to actually retrieve
the messages. So messages can be deleted, have their status changed, multiple
mail boxes can be managed, etc.
Integrated Circuit:
Another name for a chip, an IC is a small electronic device made out of a semiconductor
material.
Interface:
This is any type of point where two different things come together. Most often,
the term is used to describe the programs between you and your computer like
Windows, OS/2 and others. What you see on the screen is the interface between
you and what your computer is doing.
Interlacing:
A display technique that enables a monitor to provide more resolution inexpensively.
With interlacing monitors, the electron guns draw only half the horizontal lines
with each pass (for example, all odd lines on one pass and all even lines on
the next pass). Because an interlacing monitor refreshes only half the lines
at one time, it can display twice as many lines per refresh cycle, giving it
greater resolution. Another way of looking at it is that interlacing provides
the same resolution as non-interlacing, but less expensively.
Interleaving:
A recording method that reduces data errors during playback. Instead of the
file being written in a contiguous data stream, the data sectors are intermixed
along the recording track. If a disc should have a smudge or scratch, the entire
data file is generally recoverable because a smaller amount of the file data
is affected.
Internal Modem:
A modem that resides on an expansion board that plugs into a computer. In contrast,
an external modem is a box that attaches to a computer's COM port via cables.
Internet:
The Internet is a super-network. It connects many smaller networks together
and allows all the computers to exchange information with each other. To accomplish
this all the computers on the Internet have to use a common set of rules for
communication. Those rules are called protocols, and the Internet uses a set
of protocols called TCP/IP (Transmission Control Protocol/Internet Protocol).
Many people equate the World Wide Web with the Internet. In fact, the Internet
is like the highway, and the World Wide Web is like a truck that uses that highway
to get from place to place.
Interrupt:
A signal informing a program that an event has occurred. When a program receives
an interrupt signal, it takes a specified action (which can be to ignore the
signal). Interrupt signals can cause a program to suspend itself temporarily
to service the interrupt. Interrupt signals can come from a variety of sources.
For example, every keystroke generates an interrupt signal. Interrupts can also
be generated by other devices, such as a printer, to indicate that some event
has occurred. These are called hardware interrupts. Interrupt signals initiated
by programs are called software interrupts. A software interrupt is also called
a trap or an exception. PCs support 256 types of software interrupts and 15
hardware interrupts. Each type of software interrupt is associated with an interrupt
handler -- a routine key on your keyboard, this triggers a specific interrupt
handler. The complete list of interrupts and associated interrupt handlers is
stored in a table called the interrupt vector table, which resides in the first
1 K of addressable memory.
Intranet:
A private network for communications and sharing of information that, like the
Internet, is based on TCP/IP but is accessible only to authorized users within
an organization. An organization’s intranet is usually protected from external
access by a firewall. See also: Extranet.
IPX:
Short for Internetwork Packet Exchange, a networking protocol used by the Novell
NetWare operating systems. Like UDP/IP, IPX is a datagram protocol used for
connectionless communications. Higher-level protocols, such as SPX and NCP,
are used for additional error recovery services. The successor to IPX is the
NetWare Link Services Protocol (NLSP).
ISA:
The bus architecture used in the IBM PC/XT and PC/AT. It's often abbreviated
as ISA (pronounced as separate letters or as eye-sa) bus. The AT version of
the bus is called the AT bus and became a de facto industry standard. Starting
in the early 90s, ISA began to be replaced by the PCI local bus architecture.
Most computers made today include both an AT bus for slower devices and a PCI
bus for devices that need better bus performance. In 1993, Intel and Microsoft
introduced a new version of the ISA specification called Plug and Play ISA.
Plug and Play ISA enables the operating system to configure expansion boards
automatically so that users do not need to fiddle with DIP switches and jumpers.
ISDN:
Integrated Services Digital Network. ISDN is a public global network capable
of transmitting voice, data and images at speeds up to 2 Mbit/s. The digital
technique can transport more signals on the same telephone line than the traditional
analogue technique and enables a range of new services.
ISO:
Stands for the International Standards Organization. Someone has to say what
is the standard for transferring data. These people are it. You'll find them
in Paris.
ISP:
Internet Service Provider, a company that provides access to the Internet. For
a monthly fee, the service provider gives you a software package, username,
password and access phone number. Equipped with a modem, you can then log on
to the Internet and browse the World Wide Web and USENET, and send and receive
e-mail. In addition to serving individuals, ISPs also serve large companies,
providing a direct connection from the company's networks to the Internet. ISPs
themselves are connected to one another through Network Access Points (NAPs).
ISPs are also called IAPs (Internet Access Providers).
ISDN:
Integrated Services Digital Network.
Basically a way to move more data over regular existing phone lines. ISDN is
available to much of the USA and in most markets it is priced very comparably
to standard analog phone circuits. It can provide speeds of roughly 128,000
bits-per-second over regular phone lines. In practice, most people will be limited
to 56,000 or 64,000 bits-per-second.
Unlike DSL, ISDN can be used to connect to many different locations, one at
a time, just like a regular telephone call, as long the other location also
has ISDN.
JAVA:
A high-level programming language developed by Sun Microsystems.
JavaScript:
This is a language very close to Java that allows for more interaction with
the viewer. It is much more forgiving than Java as doesn't require it's own
window in which to work.
JPEG:
Pronounced "J-Peg." Stands for Joint Photographic Experts Group. It's
an image format that allows for compression when stored.
Jumpers:
A metal bridge that closes an electrical circuit. Typically, a jumper consists
of a plastic plug that fits over a pair of protruding pins. Jumpers are sometimes
used to configure expansion boards. By placing a jumper plug over a different
set of pins, you can change a board's parameters.
Kbit/s:
Stands for thousands of bits per second.
Kernel:
The central module of an operating system. It is the part of the operating system
that loads first, and it remains in main memory. Because it stays in memory,
it is important for the kernel to be as small as possible while still providing
all the essential services required by other parts of the operating system and
applications. Typically, the kernel is responsible for memory management, process
and task management, and disk management.
Kilobyte: (KB)
This is about a thousand bytes of space. In reality, it's two to the 10th power
or 1,024 bytes.
KVM:
Keyboard-Video-Mouse switch. A piece of hardware that connects two or more computers
to a single keyboard, monitor and mouse. Imagine you have a row of 4 computers
that all serve as file servers. Why waste money buying 4 monitors, 4 keyboards
and 4 mice. With a KVM switch you can connect all 4 computers to one monitor,
keyboard and mouse and to switch between them when needed.
LAN:
A computer network that spans a relatively small area. Most LANs are confined
to a single building or group of buildings. However, one LAN can be connected
to other LANs over any distance via telephone lines and radio waves. A system
of LANs connected in this way is called a wide area network (WAN). Most LANs
connect workstations and personal computers. Each node (individual computer
) in a LAN has its own CPU with which it executes programs, but it is also able
to access data and devices anywhere on the LAN. This means that many users can
share expensive devices, such as laser printers, as well as data. Users can
also use the LAN to communicate with each other, by sending e-mail or engaging
in chat sessions. There are many different types of LANs Ethernets being the
most common for PCs. Most Apple Macintosh networks are based on Apple's AppleTalk
network system, which is built into Macintosh computers.
LCD:
Abbreviation of liquid crystal display, a type of display used in digital watches
and many portable computers. LCD displays utilize two sheets of polarizing material
with a liquid crystal solution between them. An electric current passed through
the liquid causes the crystals to align so that light cannot pass through them.
Each crystal, therefore, is like a shutter, either allowing light to pass through
or blocking the light. Monochrome LCD images usually appear as blue or dark
gray images on top of a grayish-white background. Color LCD displays use two
basic techniques for producing color: Passive matrix is the less expensive of
the two technologies. The other technology, called thin film transistor (TFT)
or active-matrix, produces color images that are as sharp as traditional CRT
displays, but the technology is expensive. Recent passive-matrix displays using
new CSTN and DSTN technologies produce sharp colors rivaling active-matrix displays.
LED:
Abbreviation of light emitting diode, an electronic device that lights up when
electricity is passed through it. LEDs are usually red. They are good for displaying
images because they can be relatively small, and they do not burn out. However,
they require more power than LCDs.
Linux:
A version of UNIX that runs on a variety of hardware platforms including x86
PCs, Alpha, PowerPC and IBM's product line. Linux is open source software, which
is freely available; however, the full distribution of Linux along with technical
support and training are available for a fee from vendors such as Red Hat Software
and Caldera. Due to its stability, Linux has gained popularity with Internet
Service Providers as the Operating System of choice for hosting Web servers.
LVD:
Low Voltage Differential. A differential logic scheme using lower voltage levels
than HVD.
MAC layer:
Media Access Control sub layer in the network stack.
Mainframe:
Mostly a mainframe is only a mainframe when compared to a desktop computer.
It's bigger and much more powerful. Sometimes it's called a server or CPU.
MBR:
Short for Master Boot Record, a small program that is executed when a computer
boots up.
Media:
1. Objects on which data can be stored. These include hard disks, floppy disks,
CD-ROMs, and tapes.
2. In computer networks, media refers to the cables linking workstations together.
There are many different types of transmission media, the most popular being
twisted-pair wire (normal electrical wire), coaxial cable (the type of cable
used for cable television), and fiber optic cable (cables made out of glass).
3. The form and technology used to communicate information. Multimedia presentations,
for example, combine sound, pictures, and videos, all of which are different
types of media.
Megabyte: (MB)
About a million bytes of space. Actually it's 2 raised to the 20th power or
1,048,576 bytes of space.
Memory:
Internal storage areas in the computer. The term memory identifies data storage
that comes in the form of chips, and the word storage is used for memory that
exists on tapes or disks. Moreover, the term memory is usually used as a shorthand
for physical memory, which refers to the actual chips capable of holding data.
Some computers also use virtual memory, which expands physical memory onto a
hard disk. Every computer comes with a certain amount of physical memory, usually
referred to as main memory or RAM. You can think of main memory as an array
of boxes, each of which can hold a single byte of information. A computer that
has 1 megabyte of memory, therefore, can hold about 1 million bytes (or characters)
of information.
Microcomputer:
A category of computer that is generally used for personal computing, for small
business computing, and as a workstation attached to large computers or to other
small computers on a network.
Microprocessor:
A silicon chip that contains a CPU. In the world of personal computers, the
terms microprocessor and CPU are used interchangeably. At the heart of all personal
computers and most workstations sits a microprocessor. Microprocessors also
control the logic of almost all digital devices, from clock radios to fuel-injection
systems for automobiles. Three basic characteristics differentiate microprocessors:
Instruction set: The set of instructions that the microprocessor can execute.
Bandwidth: The number of bits processed in a single instruction.
Clock Speed: Given in megahertz (MHz), the clock speed determines how many instructions
per second the processor can execute.
In both cases, the higher the value, the more powerful the CPU. For example,
a 32-bit microprocessor that runs at 50MHz is more powerful than a 16-bit microprocessor
that runs at 25MHz. In addition to bandwidth and clock speed, microprocessors
are classified as being either RISC (reduced instruction set computer) or CISC
(complex instruction set computer).
MIDI:
Stands for Music Instrument Digital Interface. It allows a computer to store
and replay a musical instrument's output.
MMX:
(Multi-Media Extensions) A set of 57 multimedia instructions built into Intel's
newest microprocessors and other x86-compatible microprocessors. MMX-enabled
microprocessors can handle many common multimedia operations, such as digital
signal processing (DSP), that are normally handled by a separate sound or video
card. However, only software especially written to call MMX instructions --
so-called MMX-enabled software -- can take advantage of the MMX instruction
set. The first generation of computers with MMX chips hit the market in January,
1997.
Modem:
This is a word created out of the beginning letters of two other words: MOdulation
and DEModulation. The words mean the changing of data from digital (computer
language) to analog (phone line language) and then back again. It represents
the purpose of your computer's modem.
Motherboard:
The main circuit board of a microcomputer. The motherboard contains the connectors
for attaching additional boards. Typically, the motherboard contains the CPU,
BIOS, memory, mass storage interfaces, serial and parallel ports, expansion
slots, and all the controllers required to control standard peripheral devices,
such as the display screen, keyboard, and disk drive. Collectively, all these
chips that reside on the motherboard are known as the motherboard's chipset.
On most PCs, it is possible to add memory chips directly to the motherboard.
You may also be able to upgrade to a faster CP by replacing the CPU chip. To
add additional core features, you may need to replace the motherboard entirely.
Multiplexer:
This is a piece of hardware that allows one item to take the place of several.
An example would be using a multiplexer to allow 10 computers to attach where
only one could before.
Nanosecond:
A billionth of a second. Many computer operations, such as the speed of memory
chips, are measured in nanoseconds. Nanosecond is often abbreviated as ns.
Network:
This a system that sends and receives data.
Network Card:
Also, Network Interface Card or NIC. This is a component of a computer that
enables the computer to communicate with other computers via a direct network
connection.
Network Adapter:
This is a hardware unit that connects a device to a communication line. For
wide area networks (WAN), these adapters connect routers to the specific type
of connection (T1, BRI) that is installed. For local area networks (LAN), these
adapters connect workstations to the LAN (Ethernet or TokenRing) cabling.
NLX:
New Low Profile Extended (motherboard form factor). The NLX form factor features
a number of improvements over the previous design LPX form factor and began
heavy usage in late 1997. The popularity of the design was confirmed by massive
design use in 1998. The popularity has made it Intel's flagship line and one
of the profit leaders in chipsets. Its features include: 1. Support for larger
memory modules and DIMMs.
2. Support for the newest microprocessors, including the Pentium II using SEC
packaging.
3. Support for AGP video cards.
4. Better access to motherboard components.
5. Support for dockable designs in which the motherboard can be removed without
tools.
Node:
In networks, a processing location. A node can be a computer or some other device,
such as a printer. Every node has a unique network address, sometimes called
a Data Link Control(DLC) address or Media Access Control(MAC) address.
Noise:
Interference (static) that destroys the integrity of signals on a line. Noise
can come from a variety of sources, including radio waves, nearby electrical
wires, lightning, and bad connections. One of the major advantages of fiber
optic cables over metal cables is that they are much less susceptible to noise.
NTFS:
Short for NT File System, one of the file system for the Windows NT operating
system (Windows NT also supports the FAT file system). NTFS has features to
improve reliability, such as transaction logs to help recover from disk failures.
To control access to files, you can set permissions for directories and/or individual
files. NTFS files are not accessible from other operating such as DOS. For large
applications, NTFS supports spanning volumes, which means files and directories
can be spread out across several physical disks.
NVRAM:
(Non-Volatile Random Access Memory) Any type of memory that is made non-volatile
by connecting it to a constant power source, such as a battery. Therefore, non-volatile
memory does not lose its contents when the main power is turned off.
Operating System:
The most important program that runs on a computer. Every general-purpose computer
must have an operating system to run other programs. Operating systems perform
basic tasks, such as recognizing input from the keyboard, sending output to
the display screen, keeping track of files and directories on the disk, and
controlling peripheral devices such as disk drives and printers. For large systems,
the operating system has even greater responsibilities and powers. It is like
a traffic cop -- it makes sure that different programs and users running at
the same time do not interfere with each other. The operating system is also
responsible for security, ensuring that unauthorized users do not access the
system. Operating systems provide a software platform on top of which other
programs, called application programs, can run. The application programs must
be written to run on top of a particular operating system. Your choice of operating
system, therefore, determines to a great extent the applications you can run.
For PCs, the most popular operating systems are DOS, OS/2, and Windows, but
others are available, such as Linux. As a user, you normally interact with the
operating system through a set of commands. For example, the DOS operating system
contains commands such as COPY and RENAME for copying files and changing the
names of files, respectively. The commands are accepted and executed by a part
of the operating system called the command processor or command line interpreter.
Graphical user interfaces allow you to enter commands by pointing and clicking
at objects that appear on the screen.
Overclock:
To run a microprocessor faster than the speed for which it has been tested and
approved. Overclocking is a popular technique for eking out a little more performance
from a system. In many cases, you can force your CPU to run faster than it was
intended simply by setting a jumper on the motherboard. Overclocking does come
with some risks, however, such as over-heating, so you should become familiar
with all the pros and cons before you attempt it. Overclocking is sometimes
called speed margining.
PPP:
Stands for Point To Point Protocol. It's a software application that allows
an attachment to a server.
Parallel Port:
A parallel interface for connecting an external device such as a printer. Most
personal computers have both a parallel port and at least one serial port. On
PCs, the parallel port uses a 25-pin connector (type DB-25) and is used to connect
printers, computers and other devices that need relatively high bandwidth. It
is often called a Centronics interface after the company that designed the original
standard for parallel communication between a computer and printer. (The modern
parallel interface is based on a design by Epson.) A newer type of parallel
port, which supports the same connectors as the Centronics interface, is the
EPP (Enhanced Parallel Port) or ECP (Extended Capabilities Port). Both of these
parallel ports support bi-directional communication and transfer rates ten times
as fast as the Centronics port. Macintoshes have a SCSI port, which is parallel,
but more flexible.
Partition:
A portion of a hard disk that functions as a separate unit. A single hard disk
can be divided into several partitions, each of which functions as a separate
drive and has its own volume name (such as D:, E:, F:, and so on). The purpose
is to make the drive more efficient, as the computer can search smaller sections
for a specific file rather than the entire drive. The verb to partition refers
to the process of dividing the hard drive into partitions.
Path:
A path can be described as a file's address on your file system, describing
where the file lives: An absolute path gives the complete path, starting at
the root directory, or the very top of the file system; A relative path looks
for a file from the directory you are currently in down.
PCI:
Acronym for Peripheral Component Interconnect, a local bus standard developed
by Intel Corporation. Most modern PCs include a PCI bus in addition to a more
general ISA expansion bus. Many analysts, however, believe that PCI will eventually
supplant ISA entirely. PCI is also used on newer versions of the Macintosh computer.
PCI is a 64-bit bus, though it is usually implemented as a 32-bit bus. It can
run at clock speeds of 33 or 66 MHz. At 32 bits and 33 MHz, it yields a throughput
rate of 133 MBps. Although it was developed by Intel, PCI is not tied to any
particular family of microprocessors.
Peer to Peer:
A type of network in which each workstation has equivalent capabilities and
responsibilities. This differs from client/server architectures, in which some
computers are dedicated to serving the others. Peer-to-peer networks are generally
simpler and less expensive, but they usually do not offer the same performance
under heavy loads.
Pen Drive:
A small keyring-sized device that can be used to easily transfer files between
USB-compatible systems. Available in a range of capacities (and in some cases,
with an MP3 player built-in). Plug it in to any USB port and it will be automatically
detected by the Operating System.
PGA:
Short for Pin Grid Array, a type of chip package in which the connecting pins
are located on the bottom in concentric squares. PGA chips are particularly
good for chips that have many pins, such as modern microprocessors. Compare
with DIP and SIP.
Short for Professional Graphics Adapter, a video standard developed by IBM that
supports 640x480 resolution.
Phishing:
Short for Password Harvesting Fishing. It is the luring of sensitive information,
such as passwords and other personal information, from a victim by masquerading
as someone trustworthy with a real need for such information. Popular targets
are users of online banking services, and auction sites such as eBay. Phishers
usually work by sending out spam e-mail to large numbers of potential victims.
Typically the email will appear to come from a trustworthy company and contain
a subject and message intended to alarm the recipient into taking action. A
common approach is to tell the recipient that their account has been de-activated
due to a problem and inform them that they must take action to re-activate their
account. The user is provided with a convenient link in the same email that
takes the email recipient to a fake web page appearing to be that of a trustworthy
company. Once at that page, the user enters her personal information which is
then captured by the fraudster.
PHP:
(Hypertext Preprocessor) is a server-side, HTML-embedded scripting language
used to create dynamic Web pages. In an HTML document, PHP script (similar syntax
to that of Perl or C) is enclosed within special PHP tags. Because PHP is embedded
within tags, the author can jump between HTML and PHP (similar to ASP and Cold
Fusion) instead of having to rely on heavy amounts of code to output HTML. Because
PHP is executed on the server, the client cannot view the PHP code. PHP can
perform any task any CGI program can, but its strength lies in its compatibility
with many types of databases. Also, PHP can talk across networks using IMAP,
SNMP, NNTP, POP3 or HTTP.
PING:
Packet Internet or Inter-Network Groper; a utility used to determine whether
a particular computer is currently connected to the Internet. It works by sending
a packet to the specified IP address and waiting for a reply. The computer acronym
"PING" was contrived to match the submariners' term for the sound
of a returned sonar pulse.
Pinout:
A diagram or table that describes the purpose of each pin in a chip or connector,
or each wire in a cable.
Pixel:
Short for Picture Element, a pixel is a single point in a graphic image. Graphics
monitors display pictures by dividing the display screen into thousands (or
millions) of pixels, arranged in rows and columns. The pixels are so close together
that they appear connected. The number of bits used to represent each pixel
determines how many colors or shades of gray can be displayed. For example,
in 8-bit color mode, the color monitor uses 8 bits for each pixel, making it
possible to display 2 to the 8th power (256) different colors or shades of gray.
On color monitors, each pixel is actually composed of three dots -- a red, a
blue, and a green one. Ideally, the three dots should all converge at the same
point, but all monitors have some convergence error that can make color pixels
appear fuzzy. The quality of a display system largely depends on its resolution,
how many pixels it can display, and how many bits are used to represent each
pixel. VGA systems display 640 by 480, or about 300,000 pixels. In contrast,
SVGA systems display 1,024 by 768, or nearly 800,000 pixels. True Color systems
use 24 bits per pixel, allowing them to display more than 16 million different
colors.
Platform:
A combination of hardware and operating system you use, for example, the "NT
platform" is a PC running the Microsoft Windows NT operating system and
the "PPC platform" is a Macintosh computer with a PowerPC processor
running the Mac operating system.
Plotter:
A computer output device that draws images on paper using a pen. A plotter draws
real lines rather than simulating them as a conventional printer would by producing
a series of very close dots.
Plug-In:
This is a program that your browser uses to manipulate a downloaded file. It
differs from a Helper Application in that the plug-in works inside the browser
window.
PNP:
Short for Plug and Play, a technology developed by Microsoft and Intel that
supports plug-and-play installation. PnP is built into the Windows 95 operating
system, but to use it, the computer's BIOS and expansion boards must also support
PnP.
Port:
This is the connecting component or hardware that allows two computers to attach
to one another.
Portal:
A web site that aims to be an entry point to the World-Wide Web, typically offering
a search engine and/or links to useful pages, and possibly news or other services.
These services are usually provided for free in the hope that users will make
the site their default home page or at least visit it often. Popular examples
are Yahoo and MSN. Most portals on the Internet exist to generate advertising
income for their owners, others may be focused on a specific group of users
and may be part of an intranet or extranet. Some may just concentrate on one
particular subject, say technology or medicine, and are known as a vertical
portals.
POST:
Short for power-on self test, a series of diagnostic tests that run automatically
when you turn your computer on. The actual tests can differ depending on how
the BIOS is configured, but usually the POST tests the RAM, the keyboard, and
the disk drives. If the tests are successful, the computer boots itself. If
the tests are unsuccessful, the computer reports the error by emitting a series
of beeps and possibly displaying an error message and code on the display screen.
The number of beeps indicates the error, but differs from one BIOS to another.
POP:
Point of Presence, also Post Office Protocol
Two commonly used meanings:
A Point of Presence usually means a city or location where a network can be
connected to, often with dial up phone lines. So if an Internet company says
they will soon have a POP in Belgrade, it means that they will soon have a local
phone number in Belgrade and/or a place where leased lines can connect to their
network. A second meaning, Post Office Protocol refers to a way that e-mail
client software, such as Outlook, gets mail from a mail server. When you obtain
an account from an Internet Service Provider (ISP) you almost always get a POP
account with it, and it is this POP account that you tell your e-mail software
to use to get your mail. Another protocol called IMAP is replacing POP for email.
Primary Cache:
Primary cache is the cache located closest to the CPU. Usually, primary cache
is internal to the CPU, and secondary cache is external. Some early-model personal
computers have CPU chips that don't contain internal cache. In these cases the
external cache, if present, would actually be the primary (L1) cache.
Processor:
A processor is a device that processes programmed instructions and performs
tasks. Your processor sends and receives information from the different parts
of the system (from hardware and software). The speed at which the CPU processes
information internally is measured in MegaHertz (MHz) and GigaHertz (GHz). 1
GHz is equal to 1,000 MHz.
Protocol:
An agreed-upon format for transmitting data between two devices. The protocol
determines the following:
The type of error checking to be used.
Data compression method, if any.
How the sending device will indicate that it has finished sending a message.
How the receiving device will indicate that it has received a message.
There are a variety of standard protocols from which programmers can choose. Each
has particular advantages and disadvantages; for example, some are simpler than
others, some are more reliable, and some are faster. From a user's point of view,
the only interesting aspect about protocols is that your computer or device must
support the right ones if you want to communicate with other computers. The protocol
can be implemented either in hardware or in software.
Proxy Server:
A server that acts as an intermediary between a workstation user and the internet
so that the enterprise can ensure security, administrative control, and caching
service. A proxy server is associated with, or part of, a gateway server that
separates the enterprise network from the outside network and a firewall server
that protects the enterprise network from the outside intrusion.
PS/2 Port:
A type of port developed by IBM for connecting a mouse or keyboard to a PC.
The PS/2 port supports a mini DIN plug containing just 6 pins. Most PCs have
a PS/2 port so that the serial port can be used by another device, such as a
modem. The PS/2 port is often called the mouse port.
Quartz:
A powerful graphics system that delivers a rich imaging model, on-the-fly rendering,
anti-aliasing, and compositing of PostScript graphics. Quartz also implements
the windowing system for Mac OS X and provides low-level services such as event
handling and cursor management. It also offers facilities for rendering and
printing that use PDF as an internal model for graphics representation.
Query:
This is to make a computer request of a database.
RAID:
Short for Redundant Array of Independent (or Inexpensive) Disks, a category
of disk drives that employ two or more drives in combination for fault tolerance
and performance. RAID disk drives are used frequently on servers but aren't
generally necessary for personal computers.
RAM:
(Random Access Memory) A configuration of memory cells that hold data for processing
by a computer's central processing unit, or CPU; (see also memory). The term
random derives from the fact that the CPU can retrieve data from any individual
location, or address, within RAM.
Ranging:
The process of automatically adjusting transmit levels and time offsets of individual
modems, in order to make sure the bursts coming from different modems line up
in the right timeslots and are received at the same power level at the CMTS.
RAS:
Short for Remote Access Services, a feature built into Windows NT that enables
users to log into an NT-based LAN using a modem, X.25 connection or WAN link.
RAS works with several major network protocols, including TCP/IP, IPX, and Netbeui.
To use RAS from a remote node, you need a RAS client program, which is built
into most versions of Windows, or any PPP client software. For example, most
remote control programs work with RAS.
Real Time:
This is method of processing data the moment it is received. Batch mode is a
term used for a mainframe computer dealing with data when it has the time.
Reboot:
To restart a computer. In DOS, you can reboot by pressing the Alt, Control and
Delete keys simultaneously. This is called a warm boot. You can also perform
a cold boot by turning the computer off and then on again. On Macs, you reboot
by selecting the "Restart" option from the Special menu.
Refresh:
Generally, to update something with new data. For example, some Web browsers
include a refresh button that updates the currently display Web pages. This
feature is also called reload.
Display monitors must be refreshed many times per second. The refresh rate for
a monitor is measured in hertz (Hz) and is also called the vertical frequency,
vertical scan rate, frame rate or vertical refresh rate. The old standard for
monitor refresh rates was 60Hz, but a new standard developed by VESA sets the
refresh rate at 75Hz for monitors displaying resolutions of 640x480 or greater.
This means that the monitor redraws the display 75 times per second. The faster
the refresh rate, the less the monitor flickers.
Resolution:
Refers to the sharpness and clarity of an image. The term is most often used
to describe monitors, printers, and bit-mapped graphic images. In the case of
dot-matrix and laser printers, the resolution indicates the number of dots per
inch. For example, a 300-dpi (dots per inch) printer is one that is capable
of printing 300 distinct dots in a line 1 inch long. This means it can print
90,000 dots per square inch. For graphics monitors, the screen resolution signifies
the number of dots (pixels) on the entire screen. For example, a 640-by-480
pixel screen is capable of displaying 640 distinct dots on each of 480 lines,
or about 300,000 pixels. This translates into different dpi measurements depending
on the size of the screen. For example, a 15-inch VGA monitor (640x480) displays
about 50 dots per inch. Printers, monitors, scanners, and other I/O devices
are often classified as high resolution, medium resolution, or low resolution.
The actual resolution ranges for each of these grades is constantly shifting
as the technology improves.
Resource:
Generally, any item that can be used. Devices such as printers and disk drives
are resources, as is memory.
In many operating systems, including Microsoft Windows and the Macintosh operating
system, the term resource refers specifically to data or routines that are available
to programs. These are also called system resources.
RJ-11:
Short for Registered Jack-11, a four- or six-wire connector used primarily to
connect telephone equipment in the United States. RJ-11 connectors are also
used to connect some types of local-area networks (LANs), although RJ-45 connectors
are more common.
RJ-45:
Short for Registered Jack-45, an eight-wire connector used commonly to connect
computers onto a local-area networks (LAN), especially Ethernets. RJ-45 connectors
look similar to the ubiquitous RJ-11 connectors used for connecting telephone
equipment, but they are somewhat wider.
ROM:
Stands for Read-Only Memory. A semiconductor-based memory system that stores
information permanently and does not lose its contents when power is switched
off. ROMs are used for firmware, such as the BIOS used in the PC; and in some
portable computers, application programs and even the operating system are being
stored in ROM.
Router:
A device that connects any number of LANs. Routers use headers and a forwarding
table to determine where packets go, and they use ICMP to communicate with each
other and configure the best route between any two hosts. Very little filtering
of data is done through routers.
Routing Switch:
A switch that also performs routing operations. Usually a switch operates at
layer 2 (the Data Link layer) of the OSI Reference Model while routers operate
at layer 3 (the Network layer). Routing switches, however, perform many of the
layer 3 functions usually reserved for routers. And because the routing is implemented
in hardware rather than software, it is faster. The downside of routing switches
is that they are not as powerful or as flexible as full-fledged routers.
Screen Flicker:
The phenomenon whereby a display screen appears to flicker. Screen flicker results
from a variety of factors, the most important of which is the monitor's refresh
rate, the speed with which the screen is redrawn. If the refresh rate is too
slow, the screen will appear to glimmer. Another factor that affects screen
flicker is the persistence of the screen phosphors. Low-persistence phosphors
fade more quickly than high-persistence monitors, making screen flicker more
likely. Screen flicker can also be affected by lighting. Finally, screen flicker
is a subjective perception that affects people differently. Some people perceive
screen flicker where others do not. Most people perceive no screen flicker if
the refresh rate is 72 MHz or higher.
SCSI:
Abbreviation of Small Computer System Interface. Pronounced "scuzzy,"
SCSI is a parallel interface standard used by Apple Macintosh computers, PCs,
and many UNIX systems for attaching peripheral devices to computers. Nearly
all Apple Macintosh computers, excluding only the earliest Macs and the recent
iMac, come with a SCSI port for attaching devices such as disk drives and printers.
SCSI interfaces provide for faster data transmission rates (up to 80 megabytes
per second) than standard serial and parallel ports. In addition, you can attach
many devices to a single SCSI port, so that SCSI is really an I/O bus rather
than simply an interface. The following varieties of SCSI are currently implemented:
SCSI-1: Uses an 8-bit bus, and supports data rates of 4 MBps
SCSI-2: Same as SCSI-1, but uses a 50-pin connector instead of a 25-pin connector,
and supports multiple devices.
Wide SCSI: Uses a wider cable (168 cable lines to 68 pins) to support 16-bit
transfers.
Fast SCSI: Uses an 8-bit bus, but doubles the clock rate to support data rates
of 10 MBps.
Fast Wide SCSI: Uses a 16-bit bus and supports data rates of 20 MBps.
Ultra SCSI: Uses an 8-bit bus, and supports data rates of 20 MBps.
SCSI-3: Uses a 16-bit bus and supports data rates of 40 MBps. Also called Ultra
Wide SCSI.
Ultra2 SCSI: Uses an 8-bit bus and supports data rates of 40 MBps.
Wide Ultra2 SCSI: Uses a 16-bit bus and supports data rates of 80 MBps.
SDRAM:
Short for Synchronous Dynamic Random Access Memory, a new type of DRAM that
can run at much higher clock speeds than conventional memory. SDRAM actually
synchronizes itself with the CPU's bus and is capable of running at 100 MHz,
about three times faster than conventional FPM RAM, and about twice as fast
EDO DRAM and BEDO DRAM. SDRAM is replacing EDO DRAM in many newer computers
Today's fastest Pentium systems use CPU buses running at 100 MHz, so SDRAM can
keep up with them, though barely. Future PCs, however, are expected to have
CPU buses running at 200 MHz or faster. SDRAM is not expected to support these
high speeds which is why new memory technologies, such as RDRAM and SLDRAM,
are being developed.
Semiconductor:
A material that is neither a good conductor of electricity (like copper) nor
a good insulator (like rubber). The most common semiconductor materials are
silicon and germanium. These materials are then doped to create an excess or
lack of electrons. Computer chips, both for CPU and memory, are composed of
semiconductor materials. Semiconductors make it possible to miniaturize electronic
components, such as transistors. Not only does miniaturization mean that the
components take up less space, it also means that they are faster and require
less energy.
SEO:
(Search Engine Optimization) SEO is a process of arranging a web site's content
to obtain high rankings in various search engines (both the site and individual
pages), and includes tailoring on-page text (such as headlines and subtitles)
as well as choosing the proper keywords for a page's meta tags.
Serial Port:
A port, or interface, that can be used for serial communication, in which only
1 bit is transmitted at a time. Most serial ports on personal computers conform
to the RS-232C or RS-422 standards. A serial port is a general-purpose interface
that can be used for almost any type of device, including modems, mice, and
printers (although most printers are connected to a parallel port).
Server:
This is a mainframe computer that serves the other computers attached to it.
SGRAM:
Abbreviation of Synchronous Graphic Random Access Memory, a type of DRAM used
increasingly on video adapters and graphics accelerators. Like SDRAM, SGRAM
can synchronize itself with the CPU bus clock up to speeds of 100 MHz. In addition,
SGRAM uses several other techniques, such as masked writes and block writes,
to increase bandwidth for graphics-intensive functions. Unlike VRAM and WRAM,
SGRAM is single-ported. However, it can open two memory pages at once, which
simulates the dual-port nature of other video RAM technologies.
Shadowing:
A technique used to increase a computer's speed by using high-speed RAM memory
in place of slower ROM memory (RAM is about three times as fast as ROM). On
PCs, for example, all code to control hardware devices, such as keyboards, is
normally executed in a special ROM chip called the BIOS ROM. However, this chip
is slower than the general-purpose RAM that comprises main memory. Many PC manufacturers,
therefore, configure their PCs to copy the BIOS code into RAM when the computer
boots. The RAM used to hold the BIOS code is called shadow RAM.
Shareware:
Software distributed on the basis of an honor system. Most shareware is delivered
free of charge, but the author usually requests that you pay a small fee if
you like the program and use it regularly. By sending the small fee, you become
registered with the producer so that you can receive service assistance and
updates. You can copy shareware and pass it along to friends and colleagues,
but they too are expected to pay a fee if they use the product.
Shell:
The outermost layer of a program. Shell is another term for user interface.
Operating systems and applications sometimes provide an alternative shell to
make interaction with the program easier. For example, if the application is
usually command driven, the shell might be a menu-driven system that translates
the user's selections into the appropriate commands. Sometimes called command
shell, a shell is the command processor interface. The command processor is
the program that executes operating system commands. The shell, therefore, is
the part of the command processor that accepts commands. After verifying that
the commands are valid, the shell sends them to another part of the command
processor to be executed.
Socket:
In UNIX and some other operating systems, a software object that connects an
application to a network protocol.
A receptacle into which a plug can be inserted
A receptacle for a microprocessor or other hardware component.
Socket 7:
The form factor for fifth-generation CPU chips from Intel, Cyrix, and AMD. All
Pentium chips, except Intel's Pentium Pro (Socket 8) and Pentium II (Slot 1),
conform to the Socket 7 specifications. Intel has decided to phase out Socket
7 and replace it with Slot 1. But Intel's competitors, such as AMD and Cyrix,
are sticking with Socket 7, and are developing an enhanced version.
Socket 8:
The form factor for Intel's Pentium Pro microprocessors. The Pentium Pro was
the first microprocessor not to use the Socket 7 form factor. The Pentium II
microprocessors use an even newer form factor called Slot 1. Socket 8 is a 387-pin
ZIF socket with connections for the CPU and one or two SRAM dies for the Level
2 (L2) cache.
Software Modem:
A modem implemented entirely in software. Software modems rely on the computer's
processor to modulate and demodulate signals.
Source Code:
Computer programs or operating systems are originally written by a human being
in a programming language. This is called the source code of the software. To
be actually used by a computer, the program has to be translated by the computer
from the source code into the machine language that the computer understands
and can execute. This translation process is referred to as compiling.
Software:
This is a program, the actual code the computer reads. All other stuff is hardware.
A floppy disc is hardware.
Spam:
This is to transmit unwanted messages, usually over email, to a great many people.
Spoofing:
To fool. In networking, the term is used to describe a variety of ways in which
hardware and software can be fooled. Email spoofing, for example, involves trickery
that makes a message appear as if it came from a legitimate business email address.
SRAM:
Short for static random access memory, and pronounced ess-ram. SRAM is a type
of memory that is faster and more reliable than the more common DRAM (dynamic
RAM). The term static is derived from the fact that it doesn't need to be refreshed
like dynamic RAM.
SVGA:
Stands for Super Video Graphics Adapter. It's a high level monitor.
Swap File:
A swap file is an area on your hard disk used as virtual memory. It's called
a swap file because virtual memory management software swaps data between it
and main memory (RAM).
Switch:
In networks, a device that filters and forwards packets between LAN segments.
Switches operate at the data link layer (layer 2) of the OSI Reference Model
and therefore support any packet protocol. LANs that use switches to join segments
are called switched LANs or, in the case of Ethernet networks, switched Ethernet
LANs. A small lever or button. The switches on the back of printers and on expansion
boards are called DIP switches. A switch that has just two positions is called
a toggle switch. Another word for option or parameter -- a symbol that you add
to a command to modify the command's behavior.
Switching Hub:
Short for port-switching hub, a special type of hub that forwards packets to
the appropriate port based on the packet's address. Conventional hubs simply
rebroadcast every packet to every port. Since switching hubs forward each packet
only to the required port, they provide much better performance. Most switching
hubs also support load balancing, so that ports are dynamically reassigned to
different LAN segments based on traffic patterns. Some newer switching hubs
support both traditional Ethernet (10 Mbps) and Fast Ethernet (100 Mbps) ports.
This enables the administrator to establish a dedicated, Fast Ethernet channel
for high-traffic devices such as servers.
Synchronous:
Synchronous can refer to: (1) A communications method that transmits a group of
characters as a block of data rather than as individual characters. (2) A reference
to the fact that two different data streams are tied, or synchronized, to a single
reference clock. (3) Data transmitted in a time-division multiplexer.
TCP/IP:
Acronym for Transmission Control Protocol/Internet Protocol, the suite of communications
protocols used to connect hosts on the Internet. TCP/IP uses several protocols,
the two main ones being TCP and IP. TCP/IP is built into the UNIX operating
system and is used by the Internet, making it the de facto standard for transmitting
data over networks. Even network operating systems that have their own protocols,
such as Netware, also support TCP/IP.
Telnet:
One of the TCP/IP Protocols. It allows a connection to another computer over
dedicated phone lines.
Terabyte: (TB)
2 to the 40th power (1,099,511,627,776) bytes. This is approximately 1 trillion
bytes.
10 to the 12th power (1,000,000,000,000). This is exactly one trillion.
Terminal:
This is what you look at when you're on the Internet. It's your computer screen.
Terminator:
A device attached to the end-points of a bus network or daisy-chain. The purpose
of the terminator is to absorb signals so that they do not reflect back down
the line. Ethernet networks require a terminator at both ends of the bus, and
SCSI chains require a single terminator at the end of the chain. A character
that indicates the end of a string. In the C programming language, the null
character serves as a terminator.
Thread:
In online discussions, a series of messages that have been posted as replies
to each other. A single forum or conference typically contains many threads
covering different subjects. By reading each message in a thread, one after
the other, you can see how the discussion has evolved. You can start a new thread
by posting a message that is not a reply to an earlier message.
Throughput:
The amount of data transferred from one place to another or processed in a specified
amount of time. Data transfer rates for disk drives and networks are measured
in terms of throughput. Typically, throughputs are measured in Kbps, Mbps and
Gbps.
Transceiver:
Short for transmitter-receiver, a device that both transmits and receives analog
or digital signals. The term is used most frequently to describe the component
in local-area networks (LANs) that actually applies signals onto the network
wire and detects signals passing through the wire. For many LANs, the transceiver
is built into the network interface card (NIC). Some types of networks, however,
require an external transceiver. In Ethernet networks, a transceiver is also
called a Medium Access Unit (MAU).
Transfer Rate:
The speed at which a disk drive can transfer information between its platters
and your CPU. The transfer rate is typically measured in megabytes per second,
megabits per second, or megahertz.
Transparent:
Something that occurs without being known to the user.
Transistor:
A device composed of semiconductor material that amplifies a signal or opens
or closes a circuit. Invented in 1947 at Bell Labs, transistors have become
the key ingredient of all digital circuits, including computers. Today's microprocessors
contains tens of millions of microscopic transistors. Prior to the invention
of transistors, digital circuits were composed of vacuum tubes, which had many
disadvantages. They were much larger, required more energy, dissipated more
heat, and were more prone to failures. It's safe to say that without the invention
of transistors, computing as we know it today would not be possible.
True Color:
Refers to any graphics device or software that uses at least 24 bits to represent
each dot or pixel. Using 24 bits means that more than 16 million unique colors
can be represented. Since humans can only distinguish a few million colors,
this is more than enough to accurately represent any color image.
UDMA:
A protocol developed by Quantum Corporation and Intel that supports burst mode
data transfer rates of 33.3 MBps. This is twice as fast as the previous disk
drive standard for PCs, and is necessary to take advantage of new, faster Ultra
ATA disk drives. The official name for the protocol is Ultra DMA/33. It's also
called UDMA, UDMA/33 and DMA mode 33.
UNIX:
This is an operating system developed by AT&T. It's big push it that it
allows one server to service many different end users at one time.
UPS:
Uninterruptible Power Supply. A backup power unit that provides continuous power
when the normal power supply is interrupted. UPS systems can be stand-by, only
supplying power when the regular supply is interrupted, or fulltime, relying
on regular power and/or batteries to supply it while it supplies power to the
protected device. A UPS is not necessary on most computer systems, but can be
important on systems that need to be up 24 hours a day, such as servers.
Upstream:
The data flowing from the Cable Modem to the CMTS.
URL:
Stands for Universal Resource Locator. It's a fancy way of saying Internet Address.
USB:
Short for Universal Serial Bus, a new external bus standard that supports data
transfer rates of 12 MBps (12 million bytes per | |
By Keyword:
