Document revision date: 15 July 2002
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2.8.2 Deleting Parts of the Command Line

Pressing the Backspace key moves the cursor backwards and erases the character in that space. If line editing is enabled, you can use Ctrl/U to delete characters from the beginning of the line to the current cursor position. If line editing is not enabled, you can use Ctrl/U to cancel an entire line. The system ignores the line and redisplays the DCL prompt.

2.9 Defining Terminal Keys

A key definition is a string of characters that you assign to a particular terminal key. Use the DEFINE/KEY command. When a key is defined, you can press it instead of typing the string of characters. A key definition usually contains all or part of a command line. Using key definitions, you can customize your keyboard so that you can enter DCL commands with fewer keystrokes. When you press a defined key, the system either displays the command on your terminal or executes the command, depending on whether the command was defined using the /TERMINATE qualifier.

By default, the terminal is set to numeric keypad mode. Use the SET TERMINAL command to redefine the keys on the numeric keypad. For more information, see the descriptions of the SET TERMINAL/APPLICATION_KEYPAD, SET TERMINAL/NONUMERIC, and DEFINE/KEY commands in the OpenVMS DCL Dictionary.

2.10 Key Sequences

In addition to entering DCL commands, you can perform tasks by using specific key sequences. A key sequence is a shortcut or a way to get the system's attention while it is processing another command.

To enter a key sequence, hold down the Ctrl key while you press and release a second key. The following tables organize key sequences by function.

Table 2-1 To Enter DCL Commands
Key Sequence Function
Ctrl/Z and F10 Signals the end of the file for data entered from the terminal.
Enter Sends the current line to the system for processing. If you are not already logged in, Enter initiates a login sequence.

Table 2-2 To Interrupt DCL Commands
Key Sequence Function
Ctrl/T Momentarily interrupts terminal output to display a line of statistical information about the current process. This display includes your node and user name, the time, the name of the image you are running, and information about system resources used during your current terminal session.

You can also use Ctrl/T to determine whether the system is operating. Ctrl/T does not Enter information if the system is temporarily unresponsive or if your terminal is set to NOBROADCAST. To use Ctrl/T, you must first enter the SET CONTROL=T command (in the system login command procedure, in your personal login command procedure, or interactively).

Ctrl/Y, Ctrl/C and F6 Interrupts command processing. You can disable Ctrl/Y with the command SET NOCONTROL=Y.

Under most conditions, Ctrl/Y returns you to the DCL prompt. The program running is still active. You can enter any built-in command then continue the program with the CONTINUE command. (Press Ctrl/W to refresh the screen after you enter the CONTINUE command.)

Table 2-3 To Recall Commands
Key Sequence Function
Ctrl/B and up arrow Recalls up to 20 (VAX) or 254 (Alpha) previously entered commands.
Down arrow Displays the next line in the recall buffer.

Table 2-4 To Control Cursor Position
Key Sequence Function
Backspace Deletes the last character entered.
Ctrl/A and F14 Switches between overstrike and insert mode. The default mode (as set with the SET TERMINAL/LINE_EDITING command) is reset at the beginning of each line.
Ctrl/D and left arrow Moves the cursor one character to the left.
Ctrl/E Moves the cursor to the end of the line.
Ctrl/F and right arrow Moves the cursor one character to the right.
Ctrl/H and F12 Moves the cursor to the beginning of the line.
Ctrl/I and Tab Moves the cursor to the next tab stop on the terminal. The system provides tab stops at every eighth character position on a line. Tab settings are hardware terminal characteristics that, in general, you can modify. The Tab key also works when line editing is disabled.
Ctrl/J Deletes the word to the left of the cursor.
Ctrl/K Advances the current line to the next vertical tab stop.
Ctrl/L Moves the cursor to the beginning of the next page. This use of Ctrl/L is ignored when line editing is enabled.
Ctrl/R Repeats the current command line and leaves the cursor positioned where it was when you pressed Ctrl/R.
Ctrl/U Deletes all text in the current input line that is to the left of the cursor.
Ctrl/V Turns off some of the line editing function keys. For example, if you press Ctrl/V followed by Ctrl/D, a Ctrl/D is generated instead of the cursor moving left one character. Ctrl/D is a line terminator at DCL level.

When combined with Ctrl/V, characters that are not line terminators have no effect. Examples are Ctrl/H and Ctrl/J. However, certain control keys, such as Ctrl/U, retain their line editing functions.

Ctrl/X Cancels the current line and deletes data in the type-ahead buffer.
F7, F8, F9, F11 Reserved by Compaq.

Table 2-5 To Control Screen Display
Key Sequence Function
Ctrl/O Alternately suspends and continues display of output to the terminal. Ctrl/O displays as Output off and Output on.
Ctrl/S Suspends terminal output until Ctrl/Q is pressed.
Ctrl/Q Resumes terminal output suspended by Ctrl/S.
Ctrl/W Refreshes the screen display.

Chapter 3
Storing Information with Files

A file is a system object that contains information. This information can be machine-readable data that the computer understands. It can also be text that you enter and manipulate. The contents of a file might be the text of a document, a program, or a list of addresses. You can examine the contents of a text file by displaying it online or by printing it.

A program, also called an image or an executable image, is a file that contains instructions and data in machine-readable format. Some programs are associated with a DCL command. For example, when you type the DCL command COPY, the system runs the program SYS$SYSTEM:COPY.EXE. Some programs are started by entering the DCL command RUN followed by the program name.

Image files can be supplied by the operating system or by you and usually have the file type .EXE. You cannot examine an image file with the DCL commands TYPE, PRINT, or EDIT because image files do not consist of ASCII characters. (Text files contain ASCII characters, which are a standard method of representing the alphabet, punctuation marks, numerals, and other special symbols.)

This chapter describes how to create and manipulate files locally, and over a TCP/IP or DECnet for OpenVMS network. It includes information about:

For additional information, refer to the following:

3.1 Understanding File Names and File Specifications

A file is a unit that the OpenVMS operating system uses to store human-readable and machine-readable data. When you create or name a file, you provide information the system can use to locate and identify the file.

A filename consists of a file name and a file type. The name and type are separated by a period (.). A file also has a version number. You can have several versions of a file. Unless you specify a version number, the system uses the highest existing version number of a file. When you edit a file, the system does not modify the original version, but creates a new output file. By default, the output file has the same name and file type as the original, but has a version number that is one higher than the existing file(s) of the same name.

The file name, file type, and version number form a file specification.

3.1.1 Providing a Complete File Specification

A file is located on a specific computer (or node) in the network, on a specific device or set of devices (known as a volume) connected to that computer, in a particular directory on that volume. A complete file specification:

You do not have to include all the elements of a complete file specification. However, you must specify enough of the file specification so that, when combined with default components, the system can locate and identify the correct file.1

To override system defaults or to perform file operations over a network, you must provide a complete file specification. A complete file specification has the following format:


The components are as follows:
Node A network node or host name; applicable only to systems that support TCP/IP or DECnet. Does not apply to files stored on magnetic tape. Should not be used to specify a file on the same system that you are logged in to.
Device The term used to refer to a disk or tape drive or other peripheral connected to a computer running the OpenVMS operating system. Each device has a unique name that indicates its type and location. Disks can be formatted as ODS-2 (the default) or ODS-5 (OpenVMS Alpha only).
Directory The name of the directory in which a file is stored. Square brackets ([]) or angle brackets (<>) are used to delimit directories. Does not apply to files stored on magnetic tape.
File name The name of the file.
File type Identifies the structure or the type of the file.
Version The version number of the file. Versions are identified by a decimal number, which is incremented by 1 each time a new version of the file is created. The system automatically assigns a version number unless you specify one.

3.1.2 Rules for File Specifications

Use the following rules to specify the elements of a file specification:

For more details, refer to the Guide to OpenVMS File Applications.


Note that these rules differ for files in an environment with extended file specifications. Refer to Chapter 5 for more specific information about extended file names.

3.1.3 Default File Types Used by DCL Commands

With certain commands, if you omit the file type, the system applies a default value. The following table lists some of the more common default file types used by DCL commands:
File Type Contents
.CLD Command description file
.COM Command procedure file
.DAT Data file
.DIF Output file created by the DIFFERENCES command
.DIR Directory file
.DIS Distribution list file for the Mail utility
.EXE Executable program image file created by the linker
.HLB Help text library file
.HLP Input source file for help libraries
.INI Initialization file
.LIS Listing file created by a language compiler or assembler; default input file for the PRINT and TYPE commands
.LOG Batch job output file
.MAI Mail message file
.PS POSTSCRIPT format file
.SYS System image file
.TJL Journal file created by the DECTPU and ACL editors
.TLB Text library file
.TMP Temporary file
.TPU Command file for the EVE editor
.TPU$JOURNAL Journal file created by the EVE editor
.TXT Input file for text libraries or Mail utility output files

3.1.4 Default File Types for Language Source Programs

The following table lists the default file types for some high-level language source programs:
File Type Contents
.ADA Input source file for the Compaq Ada compiler
.BAS Input source file for the BASIC compiler
.B32 Input source file for the VAX BLISS-32 compiler
.C Input source file for the Compaq C compiler
.COB Input source file for the VAX COBOL compiler on OpenVMS VAX systems and the Compaq COBOL compiler on OpenVMS Alpha systems
.FOR Input source file for Compaq Fortran (Compaq Fortran for OpenVMS VAX systems was formerly VAX Fortran)
.M64 Input source file for the MACRO-64 assembler for OpenVMS Alpha
.MAP Memory allocation map created by the Linker utility
.MAR Input source file for the VAX MACRO assembler or the MACRO-32 Compiler for OpenVMS Alpha
.MLB Macro library for the MACRO assembler
.MSG Source file that specifies the text of messages
.OBJ Object file created by a language compiler or assembler
.OLB Object module library
.OPT Options file for input to the LINK command
.PAS Input source file for the Pascal compiler
.PLI Input source file for the PL/I compiler
.STB Symbol table file created by the Linker utility
.UPD Update file of changes for a VAX MACRO source program; also input to the SUMSLP utility


1 Record Management Services (RMS) is the OpenVMS facility that assists application programs in processing and managing files. RMS maintains the rules for file specification parsing. Refer to the Guide to OpenVMS File Applications for more information on how RMS applies defaults to partial file specifications.

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