Glossary

- A -

ADSL

Asymmetric Digital Subscriber Line
See: ADSL Forum

ANSI

American National Standards Institute

ASCII

American Standard Code for Information Interchange -- Most people think of "raw" text as ASCII--just plain text with no special features such as proportional fonts, graphics, formatting information such as full justification, etc. In ASCII data, one character is equivalent to 1 byte of memory.

AT Command

any of various commands issued to a modem for setting parameters, such as protocol usage, connections speeds, etc. The AT comes from "attention" because AT is usually entered immediately before any other commands/settings to first get the "attention" of the modem, telling it that it's about to receive commands. The original AT commands were developed by Hayes.

- B -

BinHex

BinHex -- Binary Hexadecimal encoding scheme usually used by Apple Macintosh computers.
See: RFC-1741

bis and ter

Two French words meaning second and third, respectively. These are usually found with various protocols, representing a modification to the protocol in which its attached to.
Example: V.42bis is a protocol based on V.42. See V.n for other examples.

Bit

binary digit" -- a 1 or 0, reflecting the use of a binary numbering system (only two digits) -- used because the computer recognizes either of two states: ON or OFF. 8 bits make up one byte.
Abbreviation used in this glossary: b
See also: bps

bps and Bps

bits per second / bytes per second -- bps and Bps are data transfer rates.
Common data transfer rates:
   kbps (kb/s) -- kilobits per second
   kBps (kB/s) -- kilobytes per second
   Mbps (Mb/s) -- Megabits per second
   MBps (MB/s) -- Megabytes per second
See also: bit and byte

BRI

Basic Rate Interface -- standard ISDN line, consisting of 2 B-channels and 1 D-channel.
BRI channels:
   B-Channel -- 64kbps bearer channel. Data is transmitted/received on the B-channel.
   D-Channel -- 16kbps channel that carries singaling information as well as low-speed packet data.
See also: PRI and ISDN

Byte

A byte is a unit of measurement for computer data. In terms of ASCII, one character is equivalent to one byte. Each character you're reading is a single byte. Binary data contains special information within it that may make it take up more space than the ASCII version of the same data.
Abbreviation used in this glossary: B

- C -

Cache

(Pronounced like "cash") This can be a piece of computer hardware in the form of DRAM or it can be an allocation of hard drive storage space. Its purpose is to write and/or retrieve the same data, repeatedly. Because cache memory is faster than the computer system's SRAM, operations are completed much quicker--especially if the data is repetative (same data used over and over).
In the case where cache is an allocation of hard drive space, it is usually used to store files from the internet in case you view the same data repeatedly. This saves the user from having to download the same data over and over again.

CD-ROM

See: Media Types

CGI

Common Gateway Interface
See: http://www.w3.org/pub/WWW/CGI

CPU

Central Processing Unit
-- combination of the processing unit, arithmatic logic unit (ALU), and internal memory. If these three components are contained in a single integrated circuit, it is called a microprocessor. The CPU or microprocessor can be considered the "brains" of a computer or other electronic device.

Data Compression

The ability of a modem or other device to compress data or a file before it is transmitted across the phone line or other network cable in order to make the transfer faster. The same type of data compression methods must be supported on both the transmitting end and the receiving end in order for there to be any compression. A typical compression ratio found in modems is 4:1. In reality, the likelihood of obtaining that high of a compression ratio is slim. If you've ever come across instructions telling you to set your maximum speed to 115,200 bps for a 28,800 bps modem, notice that 115,200 is 4 times 28,800. It's set that way to accomodate the 4:1 compression ratio that the modem can use.
Common types of data compression:    V.42bis -- see: V.n
   MNP 5

- D -

DCE

Data Circuit-terminating Equipment

DHCP

Dynamic Host Configuration Protocol -- DHCP automatically manages allocation of IP addresses to network resources. With DHCP, network administrators do not have to set IP addresses for different machines manually. With DHCP, a user can plug a machine into a network in different locations and automatically be assigned an IP address.

DIMM

Dual In-line Memory Module -- 168-pin (84 contacts on each side), 64-data-bit DRAM. n x 64 DIMMs are non-parity checking and n x 72 DIMMs have an extra 8 bits for parity checking.
Common types of DIMMs:
   1 x 64/72 -- 8MB capacity DIMM.
   2 x 64/72 -- 16MB
   4 x 64/72 -- 32MB
   8 x 64/72 -- 64MB
In computers, such as the Intel Pentium and Pentium Pro as well as the PowerPC (developed by Apple, IBM, and Motorola), DIMMs are addressed individually because those processors address memory 64 bits at a time.
See also: SIMM and RAM

DNS

Domain Name System -- This is a service on a computer that translates between domain names and IP addresses. When a user on a computer linked to the internet communicates with another computer on the internet, that user will typically reference the other machine by its domain name, such as "www.microsoft.com". When the user enters in that domain name to connect to, his/her machine will first contact a DNS server on the internet so that it can translate "www.microsoft.com" into an IP address, such as 207.68.137.53 so that the two computers can communicate with eachother. If a domain name is entered that the DNS server can't locate in its database, an error message is usually sent back to the person who entered it in, saying that the domain name couldn't be found or couldn't be resolved, etc.
See the following reference for a more complete explanation of how DNS works:
    The Domain Name System: A Non-Technical Explanation

Domain Name

A domain name on the internet is an alpha-numeric name given to a computer attached to the internet such as "www.microsoft.com". Domain names are used to represent IP addresses on the internet because the names are typically much easier to remember than the IP address. Because IP addresses are the addresses that are actually used "behind the scenese" across the internet, there are many DNS servers on the internet that translate between domain names and IP addresses to make it easier for people to navigate across the internet.
Internet domain names are usually structered in some form of heirarchy in what appears to be reverse order. The last part of a domain name represents the "top-level domain":

com	commercial
edu	education (mostly 4 year colleges and universities in the US)
gov	United States Federal government
int	organizations established by international treaties, or international databases
mil	United States military
net	Originally set forth for network providers, it is now synonymous with .com
org	miscillaneous organizations
us	example country code (ISO-3166), in this case representing the United States of America For much more detail on the naming of US domains, see Official United States Domain Registry and RFC-1591

Domain names (not related to the internet) represent individual computers on a LAN or other form of smaller-scale computer network.

DOS

Disk Operating System -- this term has been around for quite a few years and is just a generic term for virtually any computer's operating system. When "DOS" is mentioned, it usually represents MS-DOS, now essentially a "Dead Operating System."

Dot Pitch (dp)

A monitor's dot pitch is the distance in millimeters (mm) between the centers of the phosphors on a computer monitor. The smaller the dot pitch, the sharper the image will be, when displayed on the monitor.
Common dot pitches: .51mm, .31mm, .28mm, .26mm, .25mm, .24mm

Download

Transfer a file or other data from a "host" computer to the one you are presently using.
See also: Upload

DRAM

Dynamic RAM
See: RAM

DTE

Data Terminating Equipment

- E -

E-mail (email)

Electronic Mail

Error Control

The ability for a modem to discern between legitimate data and "noise" traveling through the phone lines.
Common types of error control:
   V.42 -- see: V.n
   MNP 2-4

External modem

A modem that is plugged into one of the serial ports on a computer. External modems often have lights on them showing current activity. Because they are external, they also have to have their own power source and power switch. Due to the case, power supply, and cable that an external modem requires, the price is usually more than an internal modem, though only by about $20.
External modems do not have UART chips built into them.

- F -

FIFO

Fast Input / Fast Output -- usually refers to the capabilities of certain data buffers, like UART chips.

Floppy Disk

See: Media Types

FTP

File Transfer Protocol -- This is a protocol used for transferring files from one machine on the internet to another.
RFC-1700 port number: 20 See also: URL
See: RFC-959

- G -

Giga

Giga is a prefix to a unit of measurement representing 10^9 (1,000,000,000) in SI (Systeme International) terms, using base-10 (decimal) numbering. In computer terms, it's the closest decimal number to 1,000,000,000 based on base-2 (binary) and is equivalent to 2^30 (1,073,741,824).
Abbreviation: G
See: Proposed prefixes for binary multiples
See also: kilo, Mega, Tera

Gopher

Gopher is no longer used as much as it used to be due to the variety of connections that the World Wide Web has to offer, but used to be another easy way of getting around on internet through series of menus.
See: RFC-1436
RFC-1700 port number: 70 Gopher was developed at the University of Minnesota.
See also: URL
gopher n.

1. Any of various short tailed, burrowing mammals of the family Geomyidae, of North America.
2. (Amer. colloq.) Native or inhabitant of Minnesota: the Gopher State.
3. (Amer. colloq.) One who runs errands, does odd-jobs, fetches or delivers documents for office staff.
4. (computer tech.) Software following a simple protocol for tunneling through a TCP/IP internet.

GUI

Graphical User Interface -- a graphical operating environment that resides on a command-line based operating system.
Examples: GEOS, Microsoft Windows, X-Windows

- H -

Hard Drive (Hard Disk)

See: Media Types

HTML

HyperText Markup Language
See: RFC-1866, and HyperText Markup Language

HTTP

HyperText Transport Protocol -- This is a protocol for retrieving multiple data-types on the internet via the WWW and the many hypertext (HTML) files containing embeded links to other files, websites, etc. (like this document).
See also: URL and RFC-2068