ACCESS
(v) (1) To use. For example, programs can access memory , which means they read data from or
write data to main memory. A user can access files, directories, computers, or peripheral devices.

(2) More specifically, access often means to read data from or write data to a mass storage device.
The time it takes to locate a single byte of information on a mass-storage device is called the access
time.

(n) (1) The act of reading data from or writing data to a storage device.

(2) A privilege to use computer information in some manner. For example, a user might be granted read
access to a file, meaning that the user can read the file but cannot modify or delete it. Most operating
systems have several different types of access privileges that can be granted or denied to specific
users or groups of users.

ASYNCHRONOUS
Not synchronized; that is, not occurring at predetermined or regular intervals. The term asynchronous
is usually used to describe communications in which data can be transmitted intermittently rather than
in a steady stream. For example, a telephone conversation is asynchronous because both parties can
talk whenever they like. If the communication were synchronous, each party would be required to wait
a specified interval before speaking.

The difficulty with asynchronous communications is that the receiver must have a way to distinguish
between valid data and noise. In computer communications, this is usually accomplished through a
special start bit and stop bit at the beginning and end of each piece of data. For this reason,
asynchronous communication is sometimes called start-stop transmission.

Most communications between computers and devices are asynchronous.

BANDWIDTH
(1) A range within a band of frequencies or wavelengths.

(2) The amount of data that can be transmitted in a fixed amount of time. For digital devices, the
bandwidth is usually expressed in bits per second(bps) or bytes per second. For analog devices, the
bandwidth is expressed in cycles per second, or Hertz (Hz).

The bandwidth is particularly important for I/O devices. For example, a fast disk drive can be hampered
by a bus with a low bandwidth. This is the main reason that new buses, such as AGP, have been
developed for the PC.

Bysinc
Short for binary synchronous, a type of synchronous communications used primarily in mainframe
networks. The de facto bisync standard is Binary Synchronous Communications (BSC) developed by
IBM. The binary part of the name signifies that the data is binary-coded. The synchronous part means
that both the sender and receiver must be synchronized before the data transfer can begin.

Bottleneck
A bottleneck refers to the delay in transmission of data through the circuits of a computer's
microprocessor or over a TCP/IP network. The delay typically occurs when a system's bandwidth
cannot support the amount of information being relayed at the speed it is being processed. There
are, however, many factors that can create a bottleneck in a system.

Bottlenecks affect microprocessor performance by slowing down the flow of information back and forth
from the CPU and the memory. If all of the components of a system are not able to feed the same
amount of data at the same speed, a delay is created. For example, a 2 GB processor will be severely
bottlenecked by an 800 MB memory bandwidth.

Bottlenecks affect network performance by slowing down the flow of information transmitted across
networks. TCP/IP connections were originally designed to transmit only text files, and the proliferation
of bandwidth-intensive transmissions such as high-resolution graphics has caused bottlenecks in the
process; therefore, the data moves more slowly across networks.

CAPI
1) (computer assisted personal interviewing) Surveying using a computer-based questionnaire. As an
alternative to paper questionnaires, CAPI allows the interviewer to customize the survey, so that
respondents answer questions only about subjects they're familiar with and receive questions in a
random order to avoid biases. CAPI also seeks to improve accessibility to data and to make the
interviewing process more entertaining. Although traditionally used on individual PCs, CAPI is now also
being administered on the Web.

(2) (common ISDN application programming interface) An application programming interface (API)
standard used to access ISDN equipment (equipment that use the integrated services digital network
[ISDN] standard for the transfer of data over telephone lines). When an application wants to
communicate with an ISDN card it sends a standard series of commands to the card. These commands
form the CAPI standard and give developers and users a chance to use a well-defined mechanism for
communications over ISDN lines without being forced to adjust to hardware idiosyncrasies.

CHANNEL
(1) In communications, the term channel refers to a communications path between two computers or
devices. It can refer to the physical medium (the wires) or to a set of properties that distinguishes
one channel from another. For example, TV channels refer to particular frequencies at which radio
waves are transmitted. IRC channels refer to specific discussions.

(2) For IBM PS/2 computers, a channel is the same as an expansion bus.

(3) In sales and marketing, the way in which a vendor communicates with and sells products to
consumers

Channel Switching
A type of communications in which a dedicated channel (or circuit) is established for the duration of a
transmission. The most ubiquitous circuit-switching network is the telephone system, which links together
wire segments to create a single unbroken line for each telephone call.

The other common communications method is packet switching, which divides messages into packets and
sends

each packet individually. The packets may take different routes and may arrive out of order. The Internet
is based on a packet-switching protocol, TCP/IP.

Circuit-switching systems are ideal for communications that require data to be transmitted in real-time.
Packet-switching networks are more efficient if some amount of delay is acceptable.

Circuit-switching networks are sometimes called connection-oriented networks. Note, however, that
although packet switching is essentially connectionless, a packet switching network can be made
connection-oriented by using a higher-level protocol. TCP, for example, makes IP networks
connection-oriented.

COM
(1) 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.

CRM
Acronym for customer relationship management. CRM entails all aspects of interaction a company has
with its customer, whether it be sales or service related. Computerization has changed the way
companies are approaching their CRM strategies because it has also changed consumer buying behavior.
With each new advance in technology, especially the proliferation of self-service channels like the Web
and WAP phones, more of the relationship is being managed electronically. Organizations are therefore
looking for ways to personalize online experiences (a process also referred to as mass customization)
through tools such as help-desk software, e-mail organizers and Web development apps.

DCC
Short for Direct Cable Connection, a Windows 95 feature that enables two computers to be connected
via a serial or parallel cable. Once connected, the two computers function as if they were on a local-area
network (LAN). Either computer can access files on the other computer. But because DCC does not
require network interface cards (NICs), it is less expensive and simpler. The limitations are that it can
connect only two PCs, and the data transfer rate is slower than with a true LAN.

EAI
Acronym for enterprise application integration. EAI is the unrestricted sharing of data and business
processes throughout the networked applications or data sources in an organization. Early software
programs in areas such as inventory control, human resources, sales automation and database
management were designed to run independently, with no interaction between the systems. They were
custom built in the technology of the day for a specific need being addressed and were often proprietary
systems. As enterprises grow and recognize the need for their information and applications to have the
ability to be transferred across and shared between systems, companies are investing in EAI in order to
streamline processes and keep all the elements of the enterprise interconnected.

There are four major categories of EAI:

Database linking: databases share information and duplicate information as needed.
Application linking: the enterprise shares business processes and data between two or more applications.
Data warehousing: data is extracted from a variety of data sources and channeled into a specific
database for analysis.
Common virtual system: the pinnacle of EAI; all aspects of enterprise computing are tied together so that
they appear as a unified application.

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.

FRAME
(1) In graphics and desktop publishing applications, a rectangular area in which text or graphics can
appear.
(2) In communications, a packet of transmitted information.
(3) In video and animation, a single image in a sequence of images. See under fps.
(4) In HTML, refers to dividing the browser display area into separate sections, each of which is really a different
Web page.

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.

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.

Host-Based
Refers to any device that relies on the host computer (that is, the computer the device is attached to)
to handle some operations. Two common examples are host-based printers and host-based modems.

Isochronous
Time-dependent. Pronounced eye-sock-ra-nuss, it refers to processes where data must be delivered
within certain time constraints. For example, multimedia streams require an isochronous transport
mechanism to ensure that data is delivered as fast as it is displayed and to ensure that the audio is
synchronized with the video.

Isochronous can be contrasted with asynchronous, which refers to processes in which data streams can
be broken by random intervals, and synchronous processes, in which data streams can be delivered only
at specific intervals. Isochronous service is not as rigid as synchronous service, but not as lenient as
asynchronous service.

Certain types of networks, such as ATM, are said to be isochronous because they can guarantee a
specified throughput. Likewise, new bus architectures, such as IEEE 1394, support isochronous delivery.

LATA
Local Access and Transport Area is a U.S. term that refers to a geographic region assigned to one or more telephone companies for providing communication services.

A connection between two telephone companies within the same region is referred to as intraLATA. A connection between two local exchange carriers in different regions is called interLATA, which is the same as long-distance service.

Provisions guiding the use of LATAs are outlined in the Telecommunications Act of 1996.

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.

Modulate
To blend data into a carrier signal. At the receiving side, a device demodulates the signals by separating the constant carrier signals from the variable data signals. For example, radio uses two types of modulation - amplitude modulation (AM) and frequency modulation (FM) - to mix audio signals with an AM or FM carrier signal. A modem modulates data by converting it to audible tones that can be transmitted on a telephone wire, and demodulates received signals to get the data.

MSA/RSA
Metropolitan Statistical Area/Rural Service Area refers to cellular service areas used by the FCC to license cellular telephone service. There are 306 MSAs and 428 RSAs. Every county in the United States is assigned to one of these markets.

MSAs -- originally used by the US government for grouping census data -- include cities of at least 50,000 people, or urbanized areas of at least 100,000 people and the counties that include these areas

RSAs include all areas not part of MSAs. These are often rural areas.

In order for a carrier to provide service to specific MSAs and RSAs, it must have a FCC license. If the carrier did receive the license at the time of auction, then it must try to buy it from the successful bidder or create a deal with the rightful owner that allows it to serve that particular area. Multiple licenses are given out per MSA/RSA, and each carrier must transmit over its assigned frequency.

If a carrier can't build a system to serve a certain percentage of the licensed area by a specified deadline date, then it must return the license to the FCC.

Multihomed
An adjective used to describe a host that is connected to two or more networks or has two or more network addresses. For example, a network server may be connected to a serial line and a LAN or to multiple LANs.

Noise
(1) In communications, 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.

(2) In general, anything that prevents a clear signal or message from being transmitted. For example, you might hear someone complain of a lot of noise in a newsgroup, meaning that there are many superfluous messages that don't add anything to the discussion.

NRZI
Non-Return-to-Zero Inverted A method for transmitting and recording data so that it keeps the sending and receiving clocks synchronized. This is especially helpful in situations where bit stuffing is employed -- the practice of adding bits to a data stream so it conforms with communications protocols. These added bits can create a long string of similar bits, which register to the receiver as a single, unchanging voltage. Since clocks adjust on voltage changes, they'll lag behind true time. NRZI ensures that after a 0 bit appears, the voltage will immediately switch to a 1 bit voltage level. These voltage changes allow the sending and receiving clocks to synchronize.

Null Modem Cable
A specially designed cable that allows you to connect two computers directly to each other via their communications ports (RS-232 ports). Null modems are particularly useful with portable computers because they enable the portable computer to exchange data with a larger system.

Parallel
Refers to processes that occur simultaneously. Printers and other devices are said to be either parallel or serial. Parallel means the device is capable of receiving more than one bit at a time (that is, it receives several bits in parallel). Most modern printers are parallel.

Protocol
An agreed-upon format for transmitting data between two devices.

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.

Remote
In networks, remote refers to files, devices, and other resources that are not connected directly to your workstation. Resources at your workstation are considered local.

Serial
One by one. Serial data transfer refers to transmitting data one bit at a time. The opposite of serial is parallel, in which several bits are transmitted concurrently.

Simplex
Refers to transmission in only one direction. Note the difference between simplex and half-duplex. Half-duplex refers to two-way communications where only one party can transmit at a time. Simplex refers to one-way communications where one party is the transmitter and the other is the receiver. An example of simplex communications is a simple radio, which you can receive data from stations but can't transmit data.

Start Bit
In asynchronous communications, the bit that signals the receiver that data is coming. Every byte of data is preceded by a start bit and followed by a stop bit.

Stop Bit
In asynchronous communications, a bit that indicates that a byte has just been transmitted. Every byte of data is preceded by a start bit and followed by a stop bit.

Synchronous
Occurring at regular intervals. The opposite of synchronous is asynchronous. Most communication between computers and devices is asynchronous -- it can occur at any time and at irregular intervals. Communication within a computer, however, is usually synchronous and is governed by the microprocessor clock. Signals along the bus, for example, can occur only at specific points in the clock cycle.

TDR
Time Domain Reflectometry is used to pinpoint flaws and problems in underground and aerial wire, cabling, and fiber optics.

Time Domain Reflectometers send a signal down the conductor and measure the time it takes for the signal -- or part of the signal -- to return. The signal's reflection begins at the flaw point. Once it returns, time is converted to distance, then divided by the speed of light, multiplied by the proper velocity of propagation (VOP), and the result is divided by two.

It is important to note that the final result does not describe the problem; it only tells the engineer where on the line to look for the problem.

Telematics
Refers to the broad industry related to using computers in concert with telecommunications systems. This includes dial-up service to the Internet as well as all types of networks that rely on a telecommunications system to transport data.

Terminal Emulation
Refers to making a computer respond like a particular type of terminal. Terminal emulation programs allow you to access a mainframe computer or bulletin board service with a personal computer.

Trunk
A communications channel between two points. It usually refers to large-bandwidth telephone channels between switching centers that handle many simultaneous voice and data signals.

A circuit from a user's terminal or PC to a network is more accurately called a line (i.e. T1 line or ISDN line) rather than a trunk, although the terms line, trunk and circuit are often used interchangeably.

UART
Pronounced u-art, and short for universal asynchronous receiver-transmitter, the UART is a computer component that handles asynchronous serial communication. Every computer contains a UART to manage the serial ports, and all internal modems have their own UART.

As modems have become increasingly fast, the UART has come under greater scrutiny as the cause of transmission bottlenecks. If you are purchasing a fast external modem, make sure that the computer's UART can handle the modem's maximum transmission rate. The newer 16550 UART contains a 16-byte buffer, enabling it to support higher transmission rates than the older 8250 UART.

Voice Recognition
The field of computer science that deals with designing computer systems that can recognize spoken words. Note that voice recognition implies only that the computer can take dictation, not that it understands what is being said. Comprehending human languages falls under a different field of computer science called natural language processing.

A number of voice recognition systems are available on the market. The most powerful can recognize thousands of words. However, they generally require an extended training session during which the computer system becomes accustomed to a particular voice and accent. Such systems are said to be speaker dependent.

Many systems also require that the speaker speak slowly and distinctly and separate each word with a short pause. These systems are called discrete speech systems. Recently, great strides have been made in continuous speech systems -- voice recognition systems that allow you to speak naturally. There are now several continuous-speech systems available for personal computers.

Because of their limitations and high cost, voice recognition systems have traditionally been used only in a few specialized situations. For example, such systems are useful in instances when the user is unable to use a keyboard to enter data because his or her hands are occupied or disabled. Instead of typing commands, the user can simply speak into a headset. Increasingly, however, as the cost decreases and performance improves, speech recognition systems are entering the mainstream and are being used as an alternative to keyboards.

VOP
Velocity of Propagation is the speed of a signal in relation to the speed of light in a vacuum (186,400 miles per second). The number 1 represents the speed of light; all other signals are a fraction of this. A cable with a VOP of.75 transmits a signal at 75% of the speed of light.

Factors that affect the velocity of propagation are various insulation materials and thicknesses.

Winsock
Short for Windows Socket, Winsock is an Application Programming Interface (API) for developing Windows programs that can communicate with other machines via the TCP/IP protocol. Windows 95 and Windows NT comes with Dynamic Link Library (DLL) called winsock.dll that implements the API and acts as the glue between Windows programs and TCP/IP connections.

In addition to the Microsoft version of winsock.dll, there are other freeware and shareware versions of winsock.dll. However, there is no official standard for the Winsock API, so each implementation differs in minor ways.