Document revision date: 19 July 1999

Delta time is an offset (a time interval) from the current date and time to a time in the future. The general format of a delta time is as follows:

"+[dddd-][hh:mm:ss.cc]"

The fields are as follows:

dddd	Number of days; an integer in the range 0 to 9999
hh	Number of hours; an integer in the range 0 to 23
mm	Number of minutes; an integer in the range 0 to 59
ss	Number of seconds; an integer in the range 0 to 59
cc	Number of hundredths of seconds; an integer in the range 0 to 99

If a qualifier is described as a value that can be expressed as an absolute time, a delta time, or a combination of the two, you must specify a delta time as if it were part of a combination time. For example, to specify a delta time value of five minutes from the current time, use "+:5" (not "0-0:5").

The following rules apply when specifying delta time:

• You can truncate a delta time on the right.
• If you specify the number of days, include a hyphen.
• You can omit fields within the time as long as you include the punctuation that separates the fields.
• If you omit the time field, the default is zero.

The following table shows some examples of delta time specifications:

Time Specification	Result
"+3-"	3 days from now (72 hours)
"+3"	3 hours from now
"+:30"	30 minutes from now
"+3-:30"	3 days and 30 minutes from now
"+15:30"	15 hours and 30 minutes from now

3.7.3 Combination Time Format

To combine absolute and delta times, specify an absolute time plus or minus a delta time. Use one of the following formats:

"[absolute time][+delta time]" [absolute time][-delta time]

The variable fields and default fields for absolute and delta time values are the same as those described in the preceding sections.

The following rules apply when specifying combination time:

• Precede the delta time value by a plus or minus sign. (Note that the minus sign is the same keyboard key as the hyphen.)
• Enclose the entire time specification in quotation marks if a plus or minus sign precedes the delta time value.
• Omit the absolute time value if you want to offset the delta time from the current date and time.
• Specify date and time information as completely as possible.

The following table shows some examples of combination time specifications:

Time Specification	Result
"+5"	5 hours from now.
"-1"	Current time minus 1 hour. The minus sign (-) indicates a negative offset. (The 1 is interpreted as an hour, not a day, because it is not followed by a hyphen.)
"+:5"	5 minutes from now.
"-:5"	Current time minus 5 minutes.
"-1-00"	Current time minus 1 day. The minus sign (-) indicates a negative offset. The hyphen (-) separates the day from the time field.
"31-DEC:+:5"	12:05 A.M. on December 31 of the current year. The absolute time specification (before the colon) defaults to midnight on December 31 of the current year. The plus sign (+) indicates a positive offset.
31-DEC:-00:10	11:50 P.M. on December 30 of the current year. The absolute time specification (before the colon) defaults to midnight on December 31 of the current year. The minus sign (-) after DEC: indicates a negative offset.

3.8 Recalling Commands

At the DCL prompt, you can recall previously typed command lines to avoid retyping long command lines. Once a command is displayed, you can reexecute or edit it.

On OpenVMS VAX systems, the recall buffer holds up to 20 previously entered commands.

On OpenVMS Alpha systems, the recall buffer holds up to 254 previously entered commands.

You can display your previously entered commands by using one of the following methods:

• Pressing Ctrl/B
• Using up arrow and down arrow keys
• Using the RECALL command

Pressing Ctrl/B once recalls the previous command line. Pressing Ctrl/B again recalls the line before the previous line and so on to the last saved command line.

3.8.2 Using Arrow Keys

Using the up arrow and down arrow keys recalls the previous and successive command, respectively. Press the arrow keys repeatedly to move through the commands.

3.8.3 Using the RECALL Command

To examine previously typed command lines, type RECALL/ALL. After reviewing the available commands, you can recall a particular command line by typing RECALL and the number of the desired command.

You can also follow RECALL with the first characters of the command line you want to display. RECALL scans the previous command lines (beginning with the most recent one) and returns the first command line that begins with the characters you typed.

Examples

1. This is a sample display generated by typing RECALL/ALL:

   $ RECALL/ALL

   1 SET DEFAULT DISK2:[MARSHALL] 2 EDIT ACCOUNTS.COM 3 PURGE ACCOUNTS.COM 4 DIRECTORY/FULL ACCOUNTS.COM 5 COPY ACCOUNTS.COM [.ACCOUNTS]* 6 SET DEFAULT [.ACCOUNTS]

2. The following example shows how to recall the fourth command line:

   $ RECALL 4

   
   After you press Return, the system displays the fourth command in the list at the DCL prompt. (The RECALL command itself is not placed in the buffer.)

3. The following example shows how to recall a previously entered command, EDIT ACCOUNTS.COM:

   $ RECALL E

   
   After you press Return, the system displays the following command line:

   $ EDIT ACCOUNTS.COM

To erase the contents of the recall buffer, enter the RECALL command with the ERASE qualifier. For example:

$ RECALL/ERASE

For security reasons, it is good practice to erase the contents of the recall buffer after you have entered commands that include passwords.

3.9 Editing the DCL Command Line

At the DCL command level, you can use many individual keys and key sequences to change what you type. Although different types of terminals have different operating characteristics, most have standard function keys and keys that can be used with line editors.

3.9.1 SHOW TERMINAL Command

To see whether line editing is enabled on your terminal, enter the SHOW TERMINAL command. The current status of line editing is displayed in the first column under Terminal Characteristics.

In the following example, line editing is not enabled:

$ SHOW TERMINAL Terminal: _VTA130: Device_Type: VT200_Series Owner: ROHBA LAT Server/Port: L121/Port_3 Physical terminal: _LTA130: Input: 9600 LFfill: 0 Width: 80 Parity: None Output: 9600 CRfill: Page: 24 Terminal Characteristics: Interactive Echo Type_ahead No Escape No Hostsync TTsync Lowercase Tab Wrap Scope No Remote No Eightbit Broadcast No Readsync No Form Fulldup No Modem No Local_echo No Autobaud Hangup No Brdcstmbx No DMA No Altypeahd Set_speed No Line Editing Insert editing No Fallback No Dialup No Secure server Disconnect No Pasthru No Syspassword No SIXEL Graphics No Soft Characters No Printer Port Numeric Keypad ANSI_CRT No Regis No Block_mode Advanced_video No Edit_mode DEC_CRT No DEC_CRT2

3.9.2 SET TERMINAL Command

You can use the SET TERMINAL command to alter the way in which your terminal edits a DCL command line. By default, changes made with the SET TERMINAL command apply only to the current session. To set the terminal each time you log in, you can include SET TERMINAL commands in your LOGIN.COM file.

SET TERMINAL/LINE_EDIT

To enable line editing, enter the SET TERMINAL/LINE_EDIT command:

$ SET TERMINAL/LINE_EDIT

SET TERMINAL/INSERT and SET TERMINAL/OVERSTRIKE

You can edit a command line in either insert or overstrike mode. In insert mode, the character you type is inserted to the left of the cursor. In overstrike mode, the character you type overwrites the character indicated by the cursor.

To change editing modes for a single command line, press Ctrl/A (Ctrl/A acts as a toggle). To change edit modes for your session, enter either the SET TERMINAL/INSERT or SET TERMINAL/OVERSTRIKE command.

SET TERMINAL/WRAP

If you use the SET TERMINAL/WRAP command, when you enter more characters than will fit on one line of the terminal screen, the text wraps to the next line.

You can edit only the line where your cursor appears. When text wraps, you cannot use the up arrow key to move the cursor up to edit the previous line. To move the cursor up to the previous line, use the Delete key and delete all the characters in the current line.

3.9.3 Deleting Portions of the Command Line

The Delete key on your keyboard is marked with either the word Rubout, the word Delete, or an X in a left-pointing arrow, depending on the type of terminal you are using. The Delete key back spaces over the most recently entered character and deletes it. On a hardcopy terminal, the deleted letters are displayed between backslash characters so you can see what is being deleted. On a video display terminal, pressing the Delete key erases the character from the screen and moves the cursor backwards.

In contrast, the Backspace key (or the left arrow key) back spaces over characters but does not delete them.

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.

3.10 Defining Terminal Keys

A key definition is a string of characters that you assign to a particular terminal key. 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.

Some definable keys are automatically enabled for definition (for example, keys PF1 to PF4 and keys F17 to F20 on LK201 keyboards). However, before you can define other keys, including KP0 (keypad 0) to KP9 and the keypad keys period, comma, minus, and Enter, you must enable them for definition by entering either the SET TERMINAL/APPLICATION_KEYPAD or the SET TERMINAL/NONUMERIC command.

3.11 Summary of Key Sequences

The following sections describe keys and key sequences that you can use to perform specific operations.

3.11.1 Keys That Enter DCL Commands

The following keys enter DCL commands:

• Ctrl/Z and F10
  Signals the end of the file for data entered from the terminal. Ctrl/Z displays as Exit. This key is available only on an LK201 keyboard.
• Return
  Sends the current line to the system for processing. On some terminals, the Return key is labeled CR. If you are not already logged in, Return initiates a login sequence.

The following keys interrupt DCL commands:

• Ctrl/C and F6
  During command entry, cancels command processing. Ctrl/C displays as Cancel. This key is available only on an LK201 keyboard.
• 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 return 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
  Interrupts command processing. Ctrl/Y displays as Interrupt. 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.)

The following keys recall commands:

• Ctrl/B or up arrow
  Recalls up to 20 (VAX) or 254 (Alpha) previously entered commands.
• Down arrow
  Displays the next line in the recall buffer.

The following keys control cursor position:

• <X|, Delete
  Deletes the last character entered at the terminal. On some terminals, the Delete key is labeled RUBOUT. The Delete key also works when line editing is disabled.
• 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. This key is available only on an LK201 keyboard.
• 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, Backspace, and F12
  Moves the cursor to the beginning of the line. This key is available only on an LK201 keyboard.
• 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, Linefeed, and F13
  Deletes the word to the left of the cursor. This key is available only on an LK201 keyboard.
• Ctrl/K
  Advances the current line to the next vertical tab stop.
• Ctrl/L
  Causes the cursor to go 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.

The following keys control screen display:

• 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.
• Hold Screen and No Scroll
  Suspends terminal output until the key is pressed again. The Hold Screen key is available only on an LK201 keyboard, and the No Scroll key is available only on a VT100 keyboard.

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