HP OpenVMS Systems Documentation

OpenVMS User's Manual

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.

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:

The components are as follows:

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:

The following table lists the default file types for some high-level language source programs: