Document revision date: 15 July 2002

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.

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:

• Understanding file names and file specifications
• Using wildcards with file names
• Other file names
• Creating and modifying files
• Displaying the contents of files
• Deleting files
• Protecting files from other users
• Printing files

For additional information, refer to the following:

• Chapter 5, for information about file names in an environment using extended file specifications
• The OpenVMS DCL Dictionary and online help, for commands discussed in this chapter
• The OpenVMS System Manager's Manual, for information about accessing remote nodes
• The Compaq TCP/IP Services for OpenVMS User's Guide, for information about using TCP/IP user utilities and commands
• The DECnet for OpenVMS Networking Manual, for information about DECnet networks
• The DECnet-Plus for OpenVMS Introduction and User's Guide, for information about DECnet Phase V networks

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:

• Precisely describes the access path the system uses to locate and identify a file
• Can include the directory in which the file is located and the network node on which the file resides
• Is also known as a network 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:

node::device:[root.][directory]file-name.file-type;version

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:

• Give the file a name that is meaningful to you. On OpenVMS Alpha and OpenVMS VAX systems with ODS-2 disks, the file name can have up to 39 characters chosen from the letters A to Z (uppercase or lowercase), the numbers 0 to 9, underscores (_), hyphens (-), tildes (~), and dollar signs ($).
• Do not use a hyphen as the first character in the file name because some older versions of OpenVMS do not allow it in all forms of a file specification.
• The file type begins with a period (.). On Alpha and VAX systems with ODS-2 disks, the file type can have up to 39 characters (including the period), chosen from the letters A through Z (which may be specified in uppercase or lowercase form), the numbers 0 through 9, underscores (_), hyphens (-), and dollar signs ($).
• A version component begins with a semicolon (;) or a period (.) When the system displays file specifications, it displays a semicolon for the version component.
• Do not use a directory field to refer to files on magnetic tape. (Directories apply only to files on disks.)
• Include a node name only if your system is part of a network and if the file is on a node other than the one you are logged in to.
• On OpenVMS Alpha and OpenVMS VAX systems with ODS-2 disks, a UFD (User File Directory) name or a subdirectory name can be 39 characters long and can contain characters chosen from the letters A through Z (which may be specified in uppercase or lowercase form), the numbers 0 through 9, underscores (_), hyphens (-), and dollar signs ($). A subdirectory name beginning with a hyphen is not allowed.
• On OpenVMS Alpha Version 7.2 or later, the sum of the numbers of characters in all of the subdirectories of the directory and root components (not including brackets and separator periods) should not exceed 512. In addition, UFD and subdirectory names have the same constraints as those for the file name, type, and version components, taking into account the fact that directories are stored as files of the form <directory-name>.DIR;1.
• In environments that consist of systems that support extended file specifications and systems that do not, remember that files and directories whose names are beyond the capabilities of the more limited systems will not be accessible from those systems.

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

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

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