Document revision date: 19 July 1999

The following table describes how the operating system responds when various keys and control characters are pressed on an LK201 keyboard (VT200 series and later terminals, and workstations). The table assumes that line editing is enabled (the default). Characters not mentioned in the table are treated as null characters.

Character	Hex	System Response
Ctrl/A	01	Switches between overstrike and insert modes
Ctrl/B	02	Recalls previous line
Ctrl/C	03	Interrupts current image (image may define alternate Ctrl/C action)
Ctrl/D	04	Moves cursor left one character
Ctrl/E	05	Moves cursor to end of line
Ctrl/F	06	Moves cursor right one character
Ctrl/H	08	Moves cursor to beginning of line
Ctrl/I	09	Horizontal tab
Ctrl/J	0A	Deletes previous word
Ctrl/M	0D	Line terminator
Ctrl/O	0F	Suspends or resumes echoing of output
Ctrl/Q	11	Resumes output (see Ctrl/S)
Ctrl/R	12	Refreshes current line
Ctrl/S	13	Suspends output (see Ctrl/Q)
Ctrl/T	14	Displays process information (must be enabled with SET CONTROL=T command)
Ctrl/U	15	Deletes characters from cursor to beginning of line
Ctrl/V	16	Passes next character or escape sequence to the image without interpreting it as described in this table
Ctrl/X	18	Purges type-ahead buffer; if characters are on the current line, deletes characters from cursor to beginning of line
Ctrl/Y	19	Interrupts current image
Ctrl/Z	1A	Indicates end of file
Data keys	--	Enters appropriate character
< X|	--	Deletes previous character
Ctrl	--	Modifies another key
Ctrl/[ (ESC)	1B	Begins escape sequence
Ctrl/F5	--	Executes answerback message
Down arrow key	--	Repeats current line
F1 (No Scroll)	--	Suspends or resumes output
F5 (Break)	--	Shuts down transmission line
F6 (Interrupt)	--	Interrupts current image
F10 (Exit)	--	Terminates current image or command procedure
F12 (Backspace)	08	Moves cursor to beginning of line
F13 (Line Feed)	--	Deletes previous word
F14 (^A)	01	Switches between overstrike and insert modes
Left arrow key	--	Moves cursor left one character
PFn	--	Can be defined (see Section 3.10)
Return	--	Line terminator
Right arrow key	--	Moves cursor right one character
Tab	--	Horizontal tab
Up arrow key	--	Repeats current line

D.2 VT100 Terminal Series

access control entry (ACE): An entry in an access control list. Access control entries may specify identifiers and the access rights to be granted or denied to the holders of the identifiers, default protection for directories, or security alarm details.

access control string: A series of 0 to 42 characters that contains login information to be sent to a remote node. On OpenVMS systems, an access control string usually consists of a user name, spaces or tabs, and a password.

account: Every user must have an account to use the system. The account is identified by the user's user name. Different accounts allow different levels of service from the system (for example, the privileges users hold, the times during which they can log in, and so on).

American Standard Code for Information Interchange (ASCII): A set of 8-bit binary numbers representing the alphabet, punctuation marks, numerals, and other special symbols used in text representation and communications protocol.

assignment statement: In DCL, the association of a symbol name with a character string or numeric value. Symbols can define synonyms for system commands or can be used as variables in command procedures.

batch job: A program that is scheduled and executed under the control of the batch processing subsystem. Control input for a batch job comes from a command procedure stored on disk and output is directed to a disk file.

break-in attempt: An effort made by an unauthorized source to gain access to the system. Because the first system access is achieved through logging in, break-in attempts primarily refer to attempts to log in illegally. These attempts focus on supplying passwords for users known to have accounts on the system through informed guesses or other trial-and-error methods.

buffer: An internal memory area used for temporary storage of data records during input or output operations.

captive account: A type of OpenVMS account that limits the activities of the user. Typically, the user is restricted to using certain command procedures and commands. For example, the user may not be allowed to use the Ctrl/Y key sequence. This type of account is synonymous with a turnkey or a tied account.

central processing unit (CPU): The hardware that handles all calculating and routing of input and output as well as executing programs. In short, the CPU is the part of the computer that actually computes.

character string: A contiguous set of bytes. A character string is identified by two attributes: an address and a length. Its address is the address of the byte containing the first character of the string; subsequent characters are stored on bytes on increasing addresses. The length is the number of characters in the string.

close: Terminating all operations on a file.

collating sequence: An order assigned to the characters of a character set (for example, ASCII, Multinational, or EBCDIC) used for sequencing purposes.

command: In DIGITAL Command Language (DCL), an instruction, generally an English word, entered by the user at a terminal or included in a command procedure. A command requests that the software monitoring a terminal or reading a command procedure perform some well-defined activity. For example, entering the COPY command requests that the system copy the contents of one file into another file.

command image: A program associated with and invoked by a DCL command.

command interpreter: A procedure-based system code that executes in supervisor mode in the context of a process to receive, to check the syntax of, and to parse commands entered by the user at a terminal or submitted in a command file.

command level: Input stream for the command interpreter. The initial input stream is always command level 0. An interactive command procedure begins executing at command level 1. A batch job command procedure begins executing at command level 0. You can use the execute procedure (@) command or the CALL command in a command procedure to create up to 32 nested command levels.

command parameter: The positional operand of a command delimited by spaces, such as a file specification, an option, or a constant.

command procedure: A file containing commands and data that the command interpreter can accept. Because command procedures provide a means of automatically passing commands to the operating system, users do not have to manually enter those commands at a terminal. In addition, command procedures permit users to employ such programming techniques as loops, counters, labels, and symbol substitution to set up elaborate command sequences that can be altered through user interaction. Command procedures can also be submitted to the system for processing as batch jobs.

command string: A line (or set of continued lines) containing a command and, optionally, information modifying the command. A command string consists of a command, its qualifiers, its parameters (file specifications, for example), and their qualifiers. A command string is normally terminated by pressing the Return key.

concatenate: The act of linking files together in a series.

CPU: See central processing unit.

cursor: An indicator used on a video terminal to point to the screen position where the next character will appear.

data: A general term referring to any representation of facts, concepts, or instructions in a form suitable for communication, interpretation, or processing.

DCL (DIGITAL Command Language): A command interpreter in an OpenVMS system that provides a means of communication between the user and the operating system.

DECnet-Plus: Family of Compaq hardware and software products that implement the Digital Network Architecture (DNA) Phase V, which integrates OSI and DNA protocols. DECnet-Plus is compliant with OSI and compatible with DECnet Phase IV and TCP/IP.

default: A value or operation that is automatically included in a command, unless the user specifies otherwise. In most cases, default settings will be what is "normal" or "expected."

default directory: The directory that the OpenVMS operating system assumes when a directory specification has not been supplied by the user.

default disk: The disk from which the system reads and to which the system writes; by default, all files that you create. The default is used whenever a file specification in a command does not explicitly name a device.

delimiter: A character that separates, terminates, or organizes elements of a character string, statement, or program.

detached process: A process that has no owner. The job controller creates a detached process when a user logs in to the system. It also creates a detached process each time it initiates a batch job or services a request for a logical link connection. Because the job controller does not own the processes it creates, these processes are referred to as detached. The DCL command RUN/UIC and the Create Process system service (specifying a UIC) allow a suitably privileged process to request creation of a detached process.

device: The general name for any peripheral connected to the processor that is capable of receiving, storing, or transmitting data. Card readers, line printers, and terminals are examples of record-oriented devices. Magnetic tape devices and disk devices are examples of mass storage devices. Terminal line interfaces and interprocessor links are examples of communications devices. Devices are not necessarily hardware.

device name: The field in a file specification that identifies the device unit on which a file is stored. Device names also include the mnemonics that identify an I/O peripheral device in a data transfer request. A device name consists of a mnemonic followed by a controller identification letter (if applicable), a unit number (if applicable), and a colon.

DIGITAL Command Language (DCL): See DCL (DIGITAL Command Language).

directory: A file that briefly catalogs a set of files stored on disk or tape. The directory includes the name, type, and version number of each file in the set, as well as a unique number that identifies the file's actual location and points to a list of its attributes. See also subdirectory.

disk: High-speed, random-access devices. There are several kinds of disks. Floppy disks are small, flexible disks. Hard disks are either fixed in place or removable. Removable disk types include a single hard disk enclosed in a protective case and a stacked set of disks enclosed in a protective case.

echo: A terminal-handling characteristic in which the characters typed by the user from the terminal keyboard are displayed on the screen or printer.

editor: A program used to create or modify text in a computer file.

equivalence string: The string associated with a logical name in a logical name table. An equivalence string can be, for example, a device name, another logical name, or a logical name concatenated with a portion of a file specification.

error message: A message sent by the system when some action you have requested fails. Each error message identifies the particular part of the operating system that detected the error. Most error messages result from typing mistakes or mistakes in specifying syntax. Often, you can correct the error by retyping the command correctly.

executable image: An image that can be run in a process. When run, an executable image is read from a file for execution in a process.

expression: Any combination of variables, constants, or both, with operators that the computer can evaluate to produce a result.

Extended File Specifications: An optional feature that removes many of the directory and file-naming restrictions previously imposed by OpenVMS. Allows deep directories and extended file names. For more information, refer to the OpenVMS Guide to Extended File Specifications.

field: A set of contiguous bytes in a logical record.

file: A set of data elements arranged in a structure significant to the user. A file is any named and stored program, data, or both, to which the system has access. Access can be of two types: read-only, meaning the file is not to be altered, and read/write, meaning the contents of the file can be altered. See also volume.

file name: The field containing a 1- to 39-character name for a file that precedes the file type in a file specification.

file specification: A unique name for a file on mass storage media. It identifies the node, the device, the directory name, the file name, the file type, and the version number under which a file is stored.

file type: The field in a file specification that consists of a period followed by a 0- to 39-character identification. By convention, this field identifies a generic class of files that have the same use or characteristics, such as compiler and assembler listing files, binary object files, and so on.

folder: A subdivision of a file in which you can store mail messages.

foreign command: A symbol that executes an image whose name is not recognized by the command interpreter as a DCL command.

foreign file specification: A file whose specification does not conform to OpenVMS syntax or format.

form feed: The movement of the cursor position to the start of a new page.

full name: Complete specification of a name in the DECdns namespace, including all parent directories in the path from the root directory to the object, directory, or soft link being named; can also include a namespace name, but not necessary when only one namespace exists in a network.

function keys: Keyboard keys that send special signals to the operating system. Function keys are referred to as Fn, where n is the number associated with that key. For example, by pressing F9 in Mail you are telling the system you want to forward a message.

generic device name: A device name that identifies the type of device but not a particular unit; a device name in which the specific controller or unit number is omitted.

global symbol: Either of the following:

1. A symbol defined in a module of a program that is potentially available for reference by another module. The linker resolves (matches references with definitions) global symbols. Contrast with local symbol.
2. A command language symbol accessible at all command levels.

hardware device: The physical computer equipment, including such mechanical devices as the line printer, the terminals, the mass storage devices, and so forth.

hardcopy terminal: Terminals that print output on paper. See also terminal.

help file: A text file in a format suitable for use with the HELP command. Help files can provide up to nine levels of search.

hierarchical directory structure: A structure of directories that has several levels arranged in a tree-like structure, based on a one-to-many relationship.

identifier: An alphanumeric string representing a user or group of users recorded in the rights database and used by the system in checking access requests. There are four types of identifiers: environmental, facility, general, and user identification code (UIC).

image: The procedures and data bound together by the linker to form an executable program. This executable program is executed by the process. There are three types of images: executable, shareable, and system.

indexed sequential file: A record file in which each record has one or more data keys embedded in it. Records in the file are individually accessible by specifying a key associated with the record.

input file: A file containing data to be transferred into the computer.

Often input and output files are confused. DCL usually prompts for these files, but most system utilities require you to identify your input and output files by position in a command line. Be sure of the syntax, or format, for the command you are using.

input stream: The source of commands and date---the user's terminal, the batch stream, or a command procedure.

interactive mode: The mode of communication with the operating system in which you enter a command and the system executes it and responds. One command has to finish executing before you can enter another.

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