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Wildcat Gold - The Optical BBS (The Golden ROM Series)(Volume 4 Number 1)(The Digital Publishing Company)(1992).ISO
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GLOSSARY
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║ GLOSSARY ║
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ANSI:
American National Standards Institute
ASCII:
American Standard for Coded Information Interchange. ASCII defines
various characters and control codes in a standard fashion.
ASCII TRANSFER PROTOCOL:
This protocol acts as if the sender is typing the characters and the
receiver is recording them. However, there is no error detection in this
protocol. Yyou can use this protocol to upload a prepared message when
connected to a BBS.
ASYNCHRONOUS DATA:
Data sent usually in parallel mode without a clock pulse. Time intervals
between transmitted bits may be of unequal lengths.
Batch Ymodem:
This protocol is a variation on Ymodem, which allows multiple files to
be sent per transfer. While transferring files, it keeps the correct
name, size, and date, and may use 128 or 1024 byte block sizes.
BAUD RATE:
Number of changes the modem's analog carrier signal goes through per
second. Not to be confused with BPS. Named for Henri Baudot. Using
muultiplexing, a signal may transfer more BPS than baudrate would
indicate, for example, a <1200> or <2400> bps modem operates at 600
baud.
BiModem:
This protocol allows simultaneous bidirectional file transfers.
BPS:
Bits per second. The data transfer rate of a serial interface (not to be
confused with BAUD). Below 600 bps, baud and bps are almost the same.
CARRIER:
A continuous frequency signal created by the modem that carries a data
signal between communicating computers over phone lines. A "NO CARRIER"
message means no connection.
CIS Quick B:
This protocol is used only on the Compuserve Information Service (CIS).
It is fast and specially suited for the networks used in accessing CIS,
which have large turnaround delays. A CIS Quick B transfer, both sending
and receiving, is totally controlled by Compuserve.
CYCLIC-REDUNDANCY-CHECK (CRC):
Used to verify data block integrity. In a typical scheme, 2 CRC bytes
are added to each user data block. The 2 bytes are computed from the
user data, by digital logical chips. The mathematical model is
polynomials with binary coefficients. When reading back data, the CRC
bytes are read and compared to new CRC bytes computed from the read back
block to detect a read error. The read back error check process is
mathematically equivalent to dividing the read block, including its CRC,
by a binomial polynomial. If the division remainder is zero, the data is
error free.
DATA:
Information processed by a computer, stored in memory, or fed into a
computer.
ECHO:
The appearance of characters (from your computer) on your screen. Full
Duplex means that the characters are remotely echoed from the receiving
computer; Half Duplex means that the characters are echoed directly from
your keyboard.
FULL DUPLEX:
Allowing data to move in either direction simultaneously. Also known
simply as DUPLEX.
HALF DUPLEX:
Able to transmit data in either direction, but in only one direction at
a time. Half duplex is actually an implementation of SIMPLEX in both
directions).
Jmodem:
This protocol is designed to maximize the amount of data that can be
transferred in a given time. It sends very long blocks of data using 16
bit CRC error correction and compressing the data wherever possible.
Kermit:
This protocol is designed to permit computers of different types to send
files to each other. Almost any computer using Kermit can be set up to
send files to another computer using Kermit.
MegaLink:
The goal of this protocol is to design and implement a protocol that is
fast, reliable and inexpensive. Megalink is a full streaming protocol.
It uses a block of 512 bytes and a CRC-32 error correction to improve
the performance.
Modem7:
Modem7 is a relative of Xmodem. It passes the filename before starting
the transfer. It is common on CP/M systems. This protocol allows more
than one file to be sent at a time.
MNP:
(Microcom Networking Protocol). A hardware-based modem error checking
method. MNP converts asynchronous data to a synchronous bit stream,
allowing the two framing bits normally required for each async character
to be dispensed with.
NULL MODEM:
A cable used to connect the serial ports of two computers in such a
fashion that each thinks it is "talking" to a modem. Very fast serial
data transfer may be acheived with a null modem.
PARITY:
A computer data checking method using an extra bit in which the total
number of binary 1's (or 0's) in a byte is always odd or always even;
thus, in an odd parity scheme, every byte has eight bits of data and one
parity bit. If using odd parity and the number of 1 bits comprising the
byte of data is not odd, the 9th or parity bit is set to 1 to create the
odd parity. In this way, a byte of data can be checked for accurate
transmission by simply counting the bits for an odd parity indication.
If the count is ever even, an error is indicated.
PROTOCOL:
A set of conventions governing the format of messages to be exchanged
within a communications system.
Puma:
This protocol has a full color display of transfer status. It can
transfer up to 99 files in a single batch using dynamic block scaling
for optimal data throughput. Like Zmodem, the resume option can continue
an interrupted transfer.
Relaxed Xmodem:
This is the same as Xmodem except that it has a longer delay time. This
is for use with remote services that can not tolerate strict timing
during Xmodem transfers.
RS-232 or RS-232C:
The standard computer hardware interface used for computer asynchronous
communications connections.
SEAlink:
SEAlink is a advanced version of Xmodem developed by System Enhancement
Associates. It is a sliding window protocol. SEAlink passes a name,
size, and date of the transferring file and allows multiple files to be
transfered.
SERIAL:
A serial interface sends a stream of data bits separated by time or an
electrical signal. For communications, serial interfaces often use a
PROTOCOL, dividing the data stream into packets which may be checksummed
to verify accuracy.
SIMPLEX:
Simplex transmission allows data to flow in one direction only (ex.,
most parallel printer interfaces or the monitor).
START/STOP BITS:
In serial, asynchronous transmission, start/stop bits indicate the
beginning and end of each 7- or 8-bit data character.
STY:
A pseudo-teletype, which is a two-way pipeline with a job on one end and
a fake keyboard-TTY on the other. Also, a standard program which
provides a pipeline from its controlling TTY to a pseudo-teletype (and
thence to another TTY, thereby providing a "sub-TTY").
SYNCHRONOUS DATA TRANSMISSION:
Data sent, usually in serial mode, with a clock pulse. No stop and start
bits are needed.
Telink:
This protocol is primarily found on Fido BBS systems. It is basically
the Xmodem protocol using CRC checking with an extra block sent ahead of
the file telling its name, size, and date. This protocol allows more
than one file to be sent at a time.
TTY:
Terminal of the teletype variety, characterized by a noisy mechanical
printer, a very limited character set, and poor print quality. Usage:
antiquated (like the TTY's themselves). Sometimes used to refer to any
terminal at all; sometimes used to refer to the particular terminal
controlling a job.
V.32:
A CCITT specification defining a family of FULL DUPLEX modems using 5
digital bits for each carrier change at a 2400 baud rate. While this
produces a raw throughput of 12,000 bps, 1 out of 5 bits is used for
error correction, reducing throughput to 9,600 bps.
X.25:
A CCITT standard that describes how data is handled in a packet-switched
network.
XMODEM:
A protocol for transferring blocks of data via modem with a high degree
of accuracy. Developed by Ward Christensen for CP/M systems in the late
'70s and now the basic standard for error-detected data transfer. Xmodem
is the most popular protocol in use today, but it is slowly being
replaced by quicker and more reliable protocols. Error checking is a
checksum or a the Cyclic Redundancy Check. The Xmodem protocol requires
a setup of no parity, 8 data bits, and 1 stop bit. While sending a
file, Xmodem always uses a 128 byte block.
Xmodem-1K:
This is a variation of Xmodem which uses blocks that may be 128 bytes or
1024 bytes in size. Most communications packages support this protocol
by allow 1K block in Xmodem protocol. Some BBS softwares refer to
Xmodem-1K as Ymodem. Ymodem sends the name, size and date of the file but
Xmodem-1K does not. If the filename 'UNKNOWN.$$$' shows in the transfer
window during a Ymodem transfer, it is likely that the BBS software is
using Xmodem-1K, in this case, you should select Xmodem protocol.
XON/XOFF:
Protocol for controlling the flow of data. If you dial into a
timesharing system in which many users simultaneously use the same
computer and if the system is about to overflow, it will send an XOFF
character to your computer. The XON character will be sent to you when
the system is ready to receive again.
Ymodem:
This is a variation of the Xmodem which uses blocks that may be 128
bytes or 1024 bytes in size and keeps the correct name, size, and date.
Ymodem-G:
This protocol is a variation on Batch Ymodem. It achieves very high
transfer rates by sending blocks one after another without waiting for
acknowledgement. This however means that an error-free link such as an
error-correcting modem or null modem cable between two computers is
needed. If an error is detected by the receiver, the transfer is
aborted. It allows transferring multiple files.
Zmodem:
This advanced protocol is both fast and reliable, and offers many
features. Zmodem can transfer a group of files in one batch, while
keeping the exact file size and dates. Zmodem detects and recovers from
errors quickly. The Zmodem Recovery feature can resume an interrupted
transfer.