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                                  GLOSSARY                                
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Adapter:  A term used to refer to printed-circuit cards that plug into a 
     computer and controls a device, such as a display or a printer.

ANSI:     American National Standards Institute
     
Autoexec.bat:  The name reserved for a batch file containing commands that are 
     carried out by DOS each time the system is started. An AUTOEXEC.BAT file
     can be used to perform desired startup procedures without having to type
     the commands each time.

Application program:     A program, such as a word processor, that performs a 
     specific task.  The term usually refers to an application of the computer
     to a particular type of work.

Archive:  Perform duplication of  files on a separate disk or on a backup tape
     for safekeeping. The DOS Backup command helps archive files.  The DOS
     Restore command can, if necessary, be used to return archived files to the
     disk from which they were backed up.

ASCII:    A standardized coding scheme that uses numeric values to represent 
     letters, numbers, symbols, and so on. ASCII is an acronym for American
     Standard Code for Information Interchange and is widely used in coding
     information for computers.

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.  You 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.

AT Command set:     A set of dialing commands used by the computer to control 
     the modem.  These commands wew developed by Hayes Microcomputer Products
     and have become a standard in the modem industry.

AUX: Short for auxiliary. The communications port DOS uses unless instructed 
     otherwise. AUX can be either COM1 or COM2 in versions of DOS through 3.2;
     it can be COM1, COM2, COM3, or COM4 in version 3.3.

Back up:  To copy one or more files to diskettes or tapes for safekeeping.  See
     Archive.  <GLOSSARY 1 20>


Backspace key: The key labeled with a single, left-pointing arrow.  It erases 
     characters you have typed.

BAK: The extension assigned by many word processors to the next-most-recent 
     version of a text file. If the working copy of a file is damaged, the BAK
     file can be used to salvage a near-current version of the document.

BASIC:    A programming language included with versions of DOS; BASIC is an 
     acronym for Beginner's All-purpose Symbolic Instruction Code.

Batch file:    A text file containing DOS commands whose extension is BAT. When
     you type the name of the batch file while DOS is at the command level, DOS
     carries out the commands contained in the file.

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 indi-
     cate, for example, a [1200] or [2400] bps modem operates at 600 baud.


Baud:     The rate at which data is transmitted over a communications link. One
     character per second equals approximately 10 baud.

BiModem:  This protocol allows simultaneous bidirectional file transfers.

Binary:   The base-2 numbering system whose only digits are 0 and 1. The binary
     system is particularly well suited to use with computers because the two
     digits can be represented by the presence (1) or absence (0) of a voltage.

Bit: The smallest unit of information used with computers; corresponds to a 
     binary digit (either 0 or 1). Eight bits make up one byte.

Boot:     To start up a computer; derived from, "Pull yourself up by your own 
     bootstraps".  A cold boot is when the computer's power is cycled.  A warm
     boot is performed by pressing the [Ctrl][Alt][Del] keys together.

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.

Byte:     The unit of measure used for computer memory and data storage. One 
     byte contains eight bits and can store one character (a letter, number, or
     punctuation mark, or other symbol).

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.  

Character string:   A group of characters that you tell DOS to treat as a set 
     of letters or numbers, rather than as a command.

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.

COBOL:    A programming lsnguage specifically designed for business applica
     tions.

Color/Graphics Adapter (CGA): A printed-circuit card in the computer that 
     controls the display. CGA shows both text and graphics at low resolution
     in up to sixteen colors.

Command file:  A file that contains the program or instructions required to 
     carry out a command. If the file's extension is COM or EXE, the command
     file contains machine instructions; if its extension is BAT, the command
     file is a batch file containing DOS commands in ASCII format.


Command:  An instruction you use to control a computer program, such as DOS or
     an application program.

Communications:     The transmission of data between computers; also called 
     telecommunications.

COMx:     Short for communications. The names of the computer's serial communi
     cations ports. All versions of DOS recognize COM1 and COM2; version 3.3
     also recognizes COM3 and COM4.

CON: Short for console. The name by which DOS refers to the keyboard (input) 
     and the display (output).

Control key:   The key labeled Ctrl which is used like the Shift key, i.e., by
     holding it down while pressing another key. The Control key usually causes
     something to happen rather than displaying a character on the screen. If
     displayed, it is shown as ^ , as in the end-of-file marker, ^ Z (Ctrl-Z). 
     The ^ symbol is called a caret.

CPU: An acronym for Central Processing Unit, it's the part of a computer that 
     performs calculations and processes information. In most microcomputers
     that use DOS the CPU is the 8086/8088, 80286, or 80386 chip.


Ctrl-Break:    The key combination to cancel a command.  Enter it by holding 
     down the Ctrl key and pressing the Break key. 

Ctrl-C:   Same as Ctrl-Break.

Ctrl-Num Lock: The key combination that stops DOS until you press any other 
     key. Usually used to freeze the display so you can view long displays. 
     Entered by holding down the Ctrl key and pressing the Num Lock key.

Ctrl-S:   Same as Ctrl-Num Lock.
     
Ctrl-Z:   The key combination that creates a special character used by DOS to 
     mark the end of a file. It's created by holding down the Ctrl key and
     pressing Z, or by pressing the function key labeled F6.

Ctrl-P:   Same as Ctrl-PrtSc.
     
Ctrl-PrtSc:    The key combination that controls simultaneous printing and 
     displaying. Press Ctrl-PrtSc once to cause DOS to print everything that is
     displayed on the screen.  Pressing Ctrl-PrtSc again causes DOS to stop
     printing. The command is entered by holding down the Ctrl key and pressing
     the PrtSc key.

Current directory:  The directory in which DOS looks for files unless otherwise
     instructed.

Current drive: The drive containing the disk on which DOS looks for a directory
     or file unless otherwise instructed.

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 file:     A file containing the information needed by a program.  The 
     information can be numbers, text, or a combination of the two.

Data:     The numbers and text processed by a computer while doing its work.
     
Data bit: A signal used in serial communications to represent the transmission
     of a character; seven or eight data bits can be used to represent one
     character.


Device name:   The name by which DOS refers to a device.  For example, DOS 
     refers to printers by, PRN, LPT1, LPT2, or LPT3.  Device names are treated
     like file names by DOS.

Device:   A piece of computer equipment that performs a specific task.  This 
     may be a monitor, printer, or disk drive.  The program that controls a
     device is called a device driver.

Directory:     The index of files that DOS maintains on a disk. The directory 
     entry for each file includes the file's name, extension, size, date and
     time it was created or last changed, and the location of the beginning of
     the file. The last item is not displayed by the Directory command.

Disk drive:    The device that rotates a disk in order to read (retrieve) and 
     write (store) information.

Disk :    A magnetically coated disk used to store information. The term is 
     used when no distinction need be made between a diskette and a fixed disk.

Diskette drive:     A disk drive used for writing data to and reading data from
     diskettes.


Diskette: A disk for storing files, made of thin plastic and enclosed in a 
     protective jacket.  AKA:   Floppy Disk.

Display:  The screen on which the computer shows both what you type at the 
     keyboard and the result of its work.  The screen is assumed by DOS to be
     the standard output device unless a different device is specified.

Drive letter:  The letter that identifies a disk drive.
     
Edit:     To change the contents of a file, usually with a word processor or an
     editing program such as Edlin.

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.

Editor:   A program used to create or change text files; also called a text 
     editor.

EDLIN:    The DOS text editor.
     


Enhanced Graphics Adapter (EGA):   A printed-circuit card in the computer that
     controls the display. EGA shows both text and graphics at medium resolu-
     tion in up to 64 colors.

Enter key:     The key you press to tell DOS that you have finished typing a 
     line.  The key is labeled "Return" on some keyboards.

Escape key:    The key labeled Esc that cancels a line you have typed but have
     not yet entered by pressing the Enter key.

Extension:     A suffix of up to three characters that can be added to a file 
     name to identify the contents of the file more precisely.

File name:     A name of up to eight characters that you assign and that DOS 
     uses to find a file on a disk.  The file name can be followed by a period
     and three additional characters called the file name extension.

File:     A named collection of information stored on a disk.  A file usually 
     contains either data or program instructions.

Filespec: The complete specification of a file.  The filespec can include a 
     drive letter, path name, file name, and an extension.


Filter command:     A DOS command that reads standard input, processes it in 
     some way and writes the result to standard output.

Fixed disk:    A disk of large capacity (10 MB or more) that cannot be removed
     from its drive. Also called a hard disk.

Floppy disk:   See diskette.  <GLOSSARY 10 2>
     
Format:   To prepare a disk for use.  AKA:  Initialize.
     
Function key:  One of several keys, usually labeled F1, F2, and so on, that 
     cause DOS (or an application program) to perform a certain function, such
     as copying characters in a line of text.

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).

Hard disk:     See fixed disk.  <GLOSSARY 12 5>
     
Hardware: The equipment that makes up a computer system, as opposed to the 
     programs, or software.

Hexadecimal:   The base-16 numbering system whose digits are 0 through F (the 
     letters A through F represent the decimal numbers 10 through 15).  The hex
     numbering is often used in computer programming because it is easily
     converted to and from binary.  Binary is the base-2 numbering system the
     computer itself uses.

Hidden file:   A file, usually used only by DOS, that is not listed when you 
     display the directory with the DOS command (DIR). Hidden files cannot be
     erased, copied, or otherwise affected by DOS commands. 

Hierarchical filing system:   See multilevel filing system.  <GLOSSARY 16 16>
     
Initialize:    See format.  <GLOSSARY 12 10>
     
Input:    The data that a program reads.
     
Input/output:  A term that refers to the devices and processes involved in the
     computer's reading (input) and writing (output) data.

I/O: Abbreviation for input/output.
     

Keyboard: The device consisting of alphabetic and other keys where instructions
     and data are typed into the computer.  The keyboard is assumed by DOS to
     be the standard input device unless a different device is specified.

Integrated circuit: An electronic device that combines thousands of transistors
     on a small sliver, or chip, of silicon. Such devices are the building
     blocks of computers. Also referred to as a chip.

Interface:     The boundary between two systems or entities, such as a disk 
     drive and the computer, or the user and a program.

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.


LPT1, LPT2, LPT3:   Short for line printer. The names that DOS uses to refer to
     the three ports to which parallel printers can be attached.


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.

Microcomputer: A small computer system, usually used by only one person.
     
Microprocessor:     An integrated circuit, or chip, that contains the circuits
     the computer needs to calculate and to communicate with the other parts of
     the system.

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. 

Modem:    A device that permits the transmission of computer data over tele
     phone lines. Contraction of modulator-demodulator.

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.


Monitor:  A device that displays computer input and output; usually used 
     synonymously with display.

Monochrome Display Adapter (MDA):  A printed-circuit card in the system unit of
     a computer that controls the display. Shows text only at medium resolution
     in one color.

Monochrome:    A term used to describe a computer display capable of displaying
     one color (usually white, green, or amber).

Multicolor Graphics Array (MCGA):  A printed-circuit card in a computer that 
     controls the display. MCGA shows both text and graphics at low to medium
     resolution in up to 256 colors, and is used in IBM PS/2 model computers.

Multilevel filing system:     A computer filing system that lets you define 
     directories within other directories, creating a structure with many
     levels.  Also called a tree-structured or hierarchical filing system.

Network:  A group of computers that share resources, such as disk drives and 
     printers.  The computers are linked together by printed-circuit cards,
     cables, and network software.



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.  

Operating system:   A program that coordinates the operation of all parts of a
     computer system.

Output:   The result of a program's processing its input data.
     
Parallel communications: A communications technique that uses multiple inter
     connecting wires to send eight bits of a byte at once (in parallel).
Parallel port: The port to which the printer is usually attached.
     

Parameter:     A qualifier that you include with a command to define more 
     specifically what you want DOS to do; also called an argument or an op-
     tion.

Parity:   An error-detection technique used for accuracy in data communica tion
                                                                           s.

Path name:     The portion of a file specification that defines the path to the
     file; can include a drive letter followed by a colon.

Path:     The list of directory names that defines the location of a directory
     to DOS.  The path statement goes into the AUTOEXEC.BAT file and follows
     the form: PATH=C:\;C:\DOS;C:\BAT;C:\WP;C:\DB;C:\UTIL

Pipe:     To direct the output of one command to be used as the input of 
     another command. The pipe symbol DOS uses is the broken vertical bar (|).

Port:     The electrical connection through which the computer sends and 
     receives data to and from devices or other computers.

Print queue:   The list of files to be printed by DOS; you create, examine, and
     modify the print queue with the Print command.  AKA:   Queue.



Printed-circuit card:    A thin, rectangular card or board, usually made of 
     fiberglass or epoxy and coated with copper. A circuit is etched into the
     copper, and electronic devices, such as integrated circuits, are soldered
     to the circuit. Computer systems are made up of these cards.

Printer:  A device that produces images of text and graphics on paper.
     
PRN: Short for printer. The printer DOS uses unless instructed otherwise. Can 
     refer to LPT1, LPT2, or LPT3.

Program:  A set of instructions for a computer.

Prompt:   A request displayed by the computer for you to provide some 
     information or perform an action.

     One of the most useful things that can be done is put the command:      

                                  prompt $p$g

     into the AUTOEXEC.BAT file.  This will tell the ANSI system to make the
     prompt indicate the name of the directory the drive is in.  Example:      
     C:\DOS> or C:DOS\UTL>

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.

Queue:    See Print Queue.  <GLOSSARY 18 21>

RAM disk: See virtual disk.  <GLOSSARY 26 21>
     
Read-only file:     A file whose read-only attribute is set so that its 
     contents can be displayed and read, but not changed.

RAM: Short for Random Access Memory. The memory that DOS uses for programs and
     data; RAM content changes often while you use the computer, and is lost
     when the computer is turned off.

Redirection:   The process of causing a command or program to take its input 
     from a file or device other than the keyboard (standard input), or of
     causing the output of a command or program to be sent to a file or device
     other than the display (standard output). The DOS redirection symbols are
     the greater-than (>) and less-than (<) signs.

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.

Replaceable parameter:   A symbolic reference, consisting of a percent sign 
     followed by a one-digit number (such as %1), that can be included with
     commands in a batch file to refer to the parameters entered with the batch
     command.

Return key:    The Enter key.
     

ROM: Short for Read-Only Memory, the type of computer memory that is permanent
     ly recorded in hardware.  ROM contains instructions that help a computer
     carry out routine tasks, such as starting itself up. The contents of ROM
     cannot be changed and are not lost (non-volatile) when the computer is
     turned off.

Root directory:     The main directory that DOS creates on each disk; the top 
     directory in a multilevel filing system.

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 Enhance
     ment 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 communications:   A communications technique that uses as few as two 
     interconnecting wires to transmit bits one after the other.

Serial port:   The communications port (COM1, COM2, COM3, or COM4) to which 
     devices, such as a modem or a serial printer, can be attached.


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.

Shareware:     Software marketing system where the user gets to use the program
     for a period of time (usually 30 days) before they are expected to
     purchase (register) the program.  Shareware is most often less expensive
     than retail software and is often times just as good or even better.

Simplex:  Simplex transmission allows data to flow in one direction only (ex.,
     most parallel printer interfaces or the monitor).

Software: The programs that are used with a computer system.
     
Standard input:     The device from which a program reads its input unless the
     input is redirected. In normal DOS operation, standard input is the
     keyboard.

Standard output:    The device to which a program sends its output unless the 
     output is redirected.  In normal DOS operation, standard output is the
     display.

Start/stop bits:    In serial, asynchronous transmission, start/stop bits 
     indicate the beginning and end of each 7- or 8-bit data character.

Stop bit: A signal used in serial communications that marks the end of a
     character.

Sructured Query Language (SQL):    A query language developed by IBM that 
     allows you to access your database.  This language can be used with a
     variety of database management products and can access databases on
     mainframes, minis, and PCs.


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").

Subdirectory:  A directory that is attached to a higher level directory.  For 
     example, in the path statement: C:\DOS\UTL, the subdirectory, UTL is
     attached to the directory DOS.

Synchronous Data Transmission:     Data sent, usually in serial mode, with a 
     clock pulse. No stop and start bits are needed.

System prompt: The characters DOS displays when it is at the command level 
     (ready to accept a command); unless you specify otherwise, the system
     prompt consists of the letter of the current drive followed by a
     greater-than sign (for example, A>).  

System program:     A program whose purpose is to control the operation of all
     or part of the computer system, such as managing the printer or interpret-
     ing commands.

Telecommunications: See communications.  <GLOSSARY 6 5>
     

Temporary file:     A file that DOS may create when told to redirect command 
     input or output; deleted by DOS when the command is completed.

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.

Text editor :  A program that you use to create or change text files. Also 
     called simply an editor.  The one supplied with the DOS system is named
     EDLIN.

Text file:     A file that you can read (contains ordinary letters, numbers, 
     and punctuation marks).

Text:     Ordinary, readable characters, including the uppercase and lowercase
     letters of the alphabet, the numerals 0 through 9, and punctuation marks.

TSR: Terminate and Stay Ready program.  Also called memory resident or pop-up
     program.  A software program that stays in memory while you run other pro-
     grams.  To get the TSR to pop up on your screen, you simply press a
     designated "hotkey" combination.


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.

Update:   To change a file, creating a new (or updated) version.
     
Video Graphics Array (VGA):   A printed-circuit card in the computer that 
     controls the display. VGA shows both text and graphics at medium to high
     resolution in up to 256 colors; used in IBM PS/2 model computers.



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. 

Virtual disk:  A portion of the computer's Random Access Memory reserved for 
     use as a simulated disk drive. Also called an electronic or RAM disk.
     Unless saved on a physical disk, the contents of a virtual disk are lost
     (volatile) when the computer is turned off.



Volume label:  An 11-character identifying name you can assign to a disk.
     
Wildcard character: A special character that, like the wild card in a card 
     game, can be used to represent any other character.  DOS recognizes two
     wildcard characters: the question mark (?), which can represent any single
     character, and the asterisk (*), which can represent more than one
     character.

Write-protect: To cover the small notch or opening on a diskette so that new or
     changed information cannot be written onto the diskette.

WYSIWYG:  What you see is what you get (pronounced "wiz-ee-wig").  A desktop 
     publishing phrease referring to the match between interfaces and printers. 
     It means that what you see on the computer screen is what you'll get on
     the printed copy.

X.25:     A CCITT standard that describes how data is handled in a packet
     switched network.




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.

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.

XON/XOFF: Protocol for controlling the flow of data. If you dial into a 
     timesharing system in which many users simultaneously use the same comput-
     er 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-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.

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.

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.

     The Zmodem protocol is a feature built into the Telix communication 
     program.
