BUZZ WORDS

By Brian Heyboer, Q-Link ID: MOSFET

FROM: HUNTSVILLE ALABAMA COMMODORE
      KOMPUTER SOCIETY (H.A.C.K.S.)
      NEWSLETTER.

This is the first article in a regular feature series of the Clearwater
Commodore Club newsletter.  In this series, I try to define some of the
computer technojargon that is so abundant.  I will try especially hard to
explain some of the harder to understand and often misused terms.

This first article concerns terms associated with telecommunications.  Many of
these terms have other meanings as well, but these additional meanings will
not be addressed here.  Unfortunately, the definitions of some words use terms
defined later.  I hope this doesn't cause any significant problem. 


Modem (Modulator/Demodulator) - a device which converts data into tones for
telephone transmission and converts received tones into data.

Intellegent Modem (aka Smart Modem) - a modem which automatically performs
many functions and/or performs complex functions with simple commands. 
[Designed to add smart features to dumb terminals, they are often used by
computers to free the terminal software from overhead control responsibility.]

BBS (Bulletin Board System) - A public access computer system on which users
may post messages to other users.

SYSOP (System Operator) - the person who runs a BBS.

E-Mail (Electronic Mail) - private messages sent via computer.

Upload - to send a program or file to another computer (usually a BBS).

Download - to receive a program or file from another computer.

Terminal (aka Dumb Terminal) - an input (usually keyboard) and output (usually
video) device for communication with a computer.

Terminal Software (aka Modem software) - software which configures a computer
to emulate (imitate) a terminal and, thus, communicate with other computers. 
[A computer emulating a terminal is often refered to as a "Smart Terminal".]

ASCII (American Standard Code for Information Interchange) - a code
established by the American National Standards Institute (ANSI) for the
electronic transmission of text data.

PETASCII (aka Commodore ASCII) - Commodore's modified ASCII, which is
incompatable with other computers and must be translated for compatability.

Baud - a measure of the rate of change of a signal on a transmission line
(number of changes per second).

Bit Rate - a measure of the rate at which data bits are transmitted, usually
in bits per second (bps).  [There is much confusion on the difference between
Baud and Bit Rate.  Common "1200 Baud" (Bell 212A compatable) modems transmit
two bits with each change in signal condition, and are really 600 Baud,
1200bps modems.]

Echo (aka True Echo) - the retransmission of received data to the sender for
display and/or error checking.

Local Echo - the display of transmitted (as opposed to echoed) data at the
origin.

Duplex (aka Full Duplex) - a mode in which simultaneous, independent, two-way
transmission is allowed.

Half Duplex - a mode in which two-way transmission, one way at a time, is
allowed.

Simplex - a mode in which all transmissions are one-way.

[There is quite a bit of industry misuse of the terms Duplex and Echo.  Since
local echo is usually required in half duplex communication, these modes are
often combined into a single transmission option (Full Duplex/True Echo or
Half Duplex/Local Echo).  This combining of functions has led to the confusion
of the term Echo with Duplex.  Since the need for half duplex operation is
rare, most sources stating "Half Duplex" really mean "Local Echo", and "Full
Duplex" means "True Echo".]

Carrier - the tone generated during idle periods. [The Mark tone by
specification.]

Originate and Answer Modes - the "channels" available for transmission.  [In
duplex systems, each user must use a different set of tones for transmission
to avoid interference.  While each unit must use different tones, it makes no
difference which party uses which mode.]

Word Length - The number of data bits in one character (an ASCII character is
called a word).  [An ASCII word is normally 8 bits long (7 data bits plus a
parity bit).  PETASCII is an 8-bit code, and the transmission of Commodore
programs requires 8 bit data.  Other encoding techniques use different word
lengths, and some terminal software allows their selection.]

Parity - an error-checking method in which an extra bit (or sometimes more
than one) is added to each word to make the bits of each word meet a certain
criteria.  Added bits are called parity bits.  [In ASCII, the parity bit is
the most significant bit and can be specified as Even or Odd (the parity bit
is set so as to produce an even or odd ones count in each word) or can be
specified as Mark (always one), Space (always zero), or Ignored (doesn't
matter).  PETASCII and other so-calle "eight-bit ASCII" use all eight bits for
data and have no parity bit.  The term "seven bit, no parity" usually means
"seven bits, Ignored parity", but it is safest to use Mark parity in such
cases if the terminal software doesn't have a "no parity" option.]

Start-Stop Transmission (aka Asyncronous Transmission) - transmission in which
words are not sent at specified intervals.  The transmission of each word is
preceeded by a Start signal and ended with a Stop signal.

Syncronous Transmission - Transmission in which words are sent at specific
intervals, usually syncronized through a shared clock signal.

Stop Bit - a bit which represents the end of a word in start-stop
transmission.  This is specified as the Mark condition.  [Some systems require
more than one Stop bit.  Since the Stop is also the idle condition, it is best
to use two stop bits when the required number is unknown.]

Start Bit - a bit that represents the start of a word.  This is specified as
the Space condition, and is always singular.

Frequency Shift Keying (FSK) - a data modulation technique whereby data is
converted into multiple tones.  [Bell 103 systems use four tones: one tone for
mark (one) and another for a space (zero) for each of two modes (originate and
answer)].

Phase Shift Keying (PSK) - a data modulation technique wherby data is
converted into different phase changes (small time shifts of a waveform). 
[Bell 212A systems use four possible phase shifts to represent two bits each,
with a separate tone used for each mode.]

Bell 103 - an FSK modem manufactured by Bell (Western Electric) which has a
maximum baud rate (and bit rate) of 300.  [This modem established the U.S.
modem standard (Bell had a monopoly on modems at the time), and all 300 baud
modems in use in this country should be "Bell 103 compatable".]

Bell 212A - a PSK Bell standard modem which transmits 1200bps at 600 baud. 
[Again, this established the U.S. standard, and all 1200bps modems for use in
this country should be "Bell 212A compatable".]

CCITT (Consultative Committee for International Telephone and Telegraph) - an
international standards organization which (among other things) established
the international standards for modems (these standards are numbered V.21 and
V.22).  [Bell 103 and 212A modems DO NOT comply with CCITT standards, but the
prevailing U.S standard for 2400bps and up modems complies with the CCITT
standard.]

RS-232C (Electronic Industries Association Recommended Standard 232, revision
C) - an industry standard for the interconnection of computer equipment. 
[This is the "standard" for connecting modems to computers.  The Commodore
User Port implements the RS-232C protocal, but needs a voltage conversion for
true RS-232C compatability.]

Protocal - a set of rules for controlling transmission.

XON/XOFF Protocal - a general purpose communications protocal where an XOFF
(ASCII character 19/Device Control 4/Control-S) controls transmission
interruption and an XON (ASCII 17/Device Control 2/Control-Q) controls
transmission resumption.

XMODEM Protocal - a popular public domain data transfer protocal in which data
is sent in "packets" with error checking codes.  [This protocal is compatable
with most computers and was originally called Christensen protocal after its
originator, Ward Christensen.]

Punter Protocal - a public domain transfer protocal similar in concept to
XMODEM, but specifically designed for Commodore computers.  [Named after its
developer, Steve Punter.]

Kermit Protocal - a public domain transfer protocal (named after the Muppet
frog) developed at Columbia University.  [This is a "rising star" among
protocals, as it includes error detection capability, is capable of sending
8-bit (program) files over a 7-bit channel (such as Tymnet), and includes a
Master-Slave mode that allows one user to control file transfer from his
terminal alone.  It is used quite extensively at universities and in industry
to transfer data between mainframe computers and microcomputers.]
 
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