You can run a TELNET session with a host that uses IBM 3270 model terminals by using the TN3270 command. The TN3270 command:

• Provides IBM 3270 Information Display System (IDS) terminal emulation.
• Assigns IBM 3270 functions to your DIGITAL keyboard.
• Assigns IDS functions to specific keys.

During a TN3270 session, you can:

• Redefine keys interactively ( Section 4.12.9.0.6).
• Redefine keys permanently ( Section 4.12.9.0.5).
• Record your sessions ( Section 4.12.5).
• Troubleshoot problems ( Section 4.12.9.1).

Table 4-5 lists the IBM 3270 terminal models that TELNET/TN3270 can emulate.

Table 4-5 TELNET --- Supported IBM 3270 Model Terminals

Model	Screen Size (Rows x Columns)
IBM 3278 Model 2	24 x 80
IBM 3278 Model 3	32 x 80
IBM 3278 Model 4	43 x 80
IBM 3278 Model 5	27 x 132

4.12.2 Setting Up Your PC or Terminal for IBM 3270 Terminal Emulation

When you use TELNET and specify IBM 3270 model terminal emulation (TN3270), the image displayed on your screen depends on:

• The type of DIGITAL terminal you use, or that your PC is emulating.
• The features you set on it.

Sections 4.12.2.1 and 4.12.2.2 explain how to set up VT200- and VT100-series terminals (or emulation on PCs), respectively.

4.12.2.1 VT200-Series Terminal Setup

Follow these steps:

1. At the Set-up Directory menu, select the keyboard type that corresponds to the keyboard layout you are using (for example, North American).
2. At the Display Set-up menu, select the following:
   • Interpret controls
   • Light text, dark screen
   • Cursor (visible)
3. At the General Set-up menu, select the following:
   • VT200 or VT100 mode (if VT100 mode, set VT100 ID)
   • 7-bit or 8-bit controls
   • Multinational/national
   • Normal cursor keys
   • No new line
4. At the Communications Set-up menu, select the following:
   • XOFF at 64 or XOFF at 128
   • 8-bit communication line
   • 8-bit (any) parity
   • No local echo
5. At the Keyboard Set-up menu, select warning bell ON.

At the DCL prompt, issue:

$ SET TERMINAL /INQUIRE

The software determines the terminal's characteristics and sets the appropriate parameters.

If you select National Character mode, issue:

$ SET TERMINAL /NOEIGHTBIT

4.12.2.2 VT100-Series Terminal Setup

Follow these steps:

1. Set your terminal to ANSI mode (see the user's guide for your terminal).
2. Enter the following command at the DCL prompt:

   $ SET TERMINAL/INQUIRE

   
   This command causes the terminal to be questioned about its characteristics. The appropriate parameters for the terminal are set up according to its response.

TN3270 requires DIGITAL terminals or DECterm windows that support at least 24 lines and 80 columns.

4.12.3 Starting and Exiting from TN3270

Start a TN3270 session by using the TN3270 command. You can also use the TELNET/TERMINAL_TYPE=IBM-3278-n command. The default terminal type is IBM-3278-2. The following examples show several ways to start a TN3270 session, using the TN3270 command and connecting to host CENTRAL. For more information, see Section 4.3.

• Using the default terminal type:

  $ TN3270 CENTRAL

• Using a terminal type other than the default:

  $ TN3270/TERMINAL_TYPE=IBM-3278-4 CENTRAL

You can invoke TN3270 and, without connecting to a remote host first, enter certain commands that customize the sessions and display parameters or status. You can also use a command file to invoke TN3270 and the customization.

The TN3270 command includes several qualifiers that allow you to specify customized or special files for the following:

• Character set translation tables file (/CHARACTER_SET=file) that translates between EBCDIC and the DIGITAL Multinational Character Set. The default file, if set up by your system manager, is SYS$LIBRARY:TN3270DEF.TBL. If this file does not exist, and you do not specify a file, TN3270 uses its own translation table.
• Keyboard definition file (/KEY_DEFINITIONS=file) that you create as an alternative to the default keyboard layout.
• National Replacement Character Set (NRCS) file (/NATIONAL_CHARACTERS=n) for which your DIGITAL terminal is configured. The default for 8-bit terminals is MULTINATIONAL. The default for 7-bit terminals is US_ASCII.

You can end a TN3270 session (close the connection) in one of the following ways:

• At the remote host's system prompt, log out.
• At the remote host's system prompt, return to the TN3270 prompt and disconnect the session, as follows:
  1. At the remote host's system prompt, press the TN3270 escape character (Ctrl/] is the default).
  2. At the TN3270 prompt, issue either DISCONNECT or close.

TN3270 displays error messages in a bordered display at the bottom of your screen. This display overwrites the status display and remains visible until you clear it. To clear, invoke one of the following functions:

• REFR
• HELP
• SET FIL
• DEF KEY

During a TN3270 session, you can record your screen's contents. The PRINT function directs your screen's contents to either a file or a spooled printer.

To record your screen's contents, follow these steps:

1. Invoke the PRINT keyboard function, as explained in Section 4.12.8.
   The screen display is recorded in a file in a compressed state. Null lines (lines with only nulls and attribute characters) do not appear.
2. Invoke the ENTER function or any function that transmits the screen contents to the remote host's application, as explained in Section 4.12.8.

This creates the default output file, TN3270PRINT.LIS. TELNET does the following:

• Each time you start a TELNET session that runs TN3270, TELNET opens a new TN3270PRINT.LIS file.
• Each time you use PRINT during a session, TELNET appends new output from the screen to the end of TN3270PRINT.LIS.
• Each time you use PRINT, if you direct the output to a printer, TELNET creates a separate entry in the print queue.
• If the printer is spooled, TELNET immediately prints the output.

You can specify a different file name. To change the name, use one of the following two methods:

• When you start a TN3270 session, use the /PRINTER qualifier. Issue:

  $ TN3270 [ host ] /PRINTER=file

• During a TN3270 session, follow these steps:
  1. Use the SET FIL keyboard function, as explained in Section 4.12.8.
  2. At the prompt for a new file name, enter a name.
     If you specify the same name that is already in use, subsequent PRINT operations direct output to a new version of the same file.
  3. Use the NEW LINE keyboard function, as explained in Section 4.12.8.

Online help during a TN3270 session displays:

• A picture of the keypad
• A list of TN3270 keyboard functions
• The key combinations that invoke the TN3270 keyboard functions

The Help screen shows the TN3270 functions as they correspond to the keys on your physical keyboard:

• Top-row keys
• Editing keypad
• Application keypad
• Up to 32 control or extended character definitions
• All your definitions and changes, including those you make interactively

To see the Help screen, use the HELP function which is key F15.

4.12.7 If the Keyboard Locks

If your keyboard locks, the terminal bell rings, and the status line displays:

Inhib

To unlock the keyboard, press the following key to invoke the RESET function (KP0 refers to the 0 key in the application keypad on the right hand side of the keyboard):

[KP0]

Do not use the following functions when the cursor is in a protected field (a field that does not accept user input):

• DELETE
• DUP
• ER EOF
• FM
• Any graphic character

This section describes the keyboard functions. Preceding each function description are the key sequences for VT100 and VT200 terminals and the function name to use in a DEFINE/KEY command. In many of the key sequences, TN3270 allows use of the extended function (EXT) feature. Used in conjunction with another key, EXT allows access to an extended function for that key. The extended function feature is described below in more detail.

ATTACH

VT100: EXT + E	VT200: EXT + Find
DEFINE_KEY Function: ATTACH

Changes control from one subprocess to another subprocess or to the parent process. When you invoke the ATTACH function, TN3270 uses the name of the last process to which you attached as the default process name.

If you want to attach to a different process, press Ctrl/U to erase the default process name. You can then enter the process name of your choice at the prompt. The process name can be a quoted string. Use the quotation marks to preserve spaces, tabs, or lowercase letters in strings.

ATTN

VT100: EXT + A	VT200: F19
DEFINE_KEY Function: ATTENTION

Provides a way to "get the attention of" the remote application program that you are running by sending a SIGNAL RU command to the remote host. See the user's guide of the particular application program to learn what response the program gives when you use this key.

Back Tab (| Left arrow)

VT100: BACKSPACE	VT200: F12
DEFINE_KEY Function: BACK_TAB

Moves the cursor, depending on the type of screen. On a formatted screen, the cursor moves one of these ways, depending on the location when you press this key:

• If the cursor is in a field, but not at the first position of the field, it moves to the beginning of the unprotected field that it is in.
• If the cursor is in the first position of a field, it moves to the beginning of the preceding unprotected field. If the cursor is in the first position of the first unprotected field, the cursor moves to the first position of the last unprotected field on the screen.

On an unformatted screen, the cursor returns to the first position on the screen.

Cent Sign (¢)

VT100: EXT + C	VT200: EXT + C
DEFINE_KEY Function: (None)

Enters a cent sign. If your terminal does not have this character, your screen displays a hyphen ( - ).

CLEAR

VT100: EXT + Enter	VT200: EXT + F20
DEFINE_KEY Function: CLEAR

Clears the screen and moves the cursor to the first position on the screen. When you invoke the CLEAR function, the software notifies the application program that this function has been used.

DEF KEY (DEFINE key)

VT100: Ctrl/K	VT200: Ctrl/K
DEFINE_KEY Function: DEFINE_KEY

Lets you interactively define or redefine a key. You get a prompt for the name of the key to define and for a function you want to assign to that key. Refer to Section 4.12.9 for more information about using the DEF KEY function.

DELETE

VT100: Delete	VT200: <X]
DEFINE_KEY Function: DELETE

Deletes the character at the cursor. The cursor remains where it is, and the other characters to the right of the cursor in the same field move one position to the left. The end of the field fills with blanks. Note that this is not the action normally associated with the Delete key on DIGITAL terminals.

DSP ATT (display attributes)

VT100: Ctrl/V	VT200: EXT + F17
DEFINE_KEY Function: DISPLAY_ATTRIBUTES

Enables and disables the visible attribute mode. This mode of operation forces display of the attribute characters (that is, the characters at the start of a field that indicate the display and data type of that field). In IBM 3270 model terminal emulation (TN3270), you can use the DSP ATT function to debug application programs, as explained in Section 4.12.10.

DUP (duplicate)

VT100: EXT + *	VT200: EXT + F12
DEFINE_KEY Function: DUP

Lets you enter a value in the same field in several forms without needing to repeat the entry for each form.

After entering the data in the field on the first form, use the DUP function when at the same field on succeeding forms. The application program makes the necessary translation, filling in these fields with the same value. For details about the use of this key, refer to the user's guide of the particular application program.

Displays an asterisk (*).

DV CNCL (device cancel)

VT100: EXT + U	VT200: EXT + Remove
DEFINE_KEY Function: DVCNCL

Cancels the RECORD function. Use the DV CNCL function if you begin using the RECORD function and then decide you want to stop. If you want to delete a sequence that has already been recorded on a PF key, use the RECORD function, press the PF key, and then use the DV CNCL function.

ENTER

VT100: Line Feed + Enter	VT200: Do + Enter
DEFINE_KEY Function: ENTER

Sends your input to the remote application program. While this communication is active, the keyboard locks and Inhib appears on the status line. Usually the application program releases the keyboard when it has finished processing your input.

ER EOF (erase to the end of the field)

VT100: EXT + KP,	VT200: F18
DEFINE_KEY Function: ERASE_EOF

Erases the contents of the current field, from the location of the cursor to the end of the field. The cursor remains in the same location.

ER INP (erase input)

VT100: EXT + KP-	VT200: EXT + F18
DEFINE_KEY Function: ERASE_INPUT

On a formatted screen, clears all the data in the unprotected fields on your screen and moves the cursor to the first position in the first unprotected field on the screen.

On an unformatted screen, clears all the data and moves the cursor to the first position on the screen.

You can also use the ER INP function to remove all previously recorded key sequences by using the RECORD function and then the ER INP function.

EXIT

VT100: Ctrl/Z or F10	VT200: Ctrl/Z or F10
DEFINE_KEY Function: EXIT

Terminates the remote TELNET/TN3270 session. Aborts any exchange of data in progress between the local and remote hosts. Note that terminating a session with the IBM host in this way may result in improper termination of the session. For the appropriate logoff command string, see the user's guide for the IBM application with which you are communicating.

EXT (extended function)

VT100: KP.	VT200: KP.
DEFINE_KEY Function: EXTEND

Used in conjunction with another key, allows access to an extended function for that key. First invoke the EXT function and then press the second key. If you invoke EXT accidentally, invoking the RESET function cancels the EXT function.

If the status display is enabled when you invoke the EXT function, the word Extend appears on the status line.

FM (field mark)

VT100: EXT + ;	VT200: EXT + F13
DEFINE_KEY Function: FM

Specifies the end of a field on an unformatted screen or the end of part of an unprotected field on a formatted screen. Refer to the user's guide of the remote application program for specific use of this key.

Displays a semicolon ( ; ).

HELP

VT100: EXT + H	VT200: Help
DEFINE_KEY Function: HELP

Displays online help and an illustration of the TN3270 keyboard.

HOME

VT100: EXT + B	VT200: F13
DEFINE_KEY Function: HOME

Repositions the cursor to the first position in the first unprotected field on the screen (that is, to the beginning of the input area on the screen).

Horizontal Control (Right arrow and Left arrow)

VT100: Right arrow or Left arrow	VT200: Right arrow or Left arrow
DEFINE_KEY Function: RIGHT, RIGHT_NOWRAP, LEFT, or LEFT_NOWRAP

Moves the cursor horizontally across your screen without changing data you have already entered. If the cursor is at the:

• End of a line when you use the Right arrow function, the cursor moves to the start of the next line.
• Beginning of a line when you use the Left arrow function, the cursor moves to the end of the previous line.
  If the screen display you receive is wider than 80 columns, you can use the Right arrow and Left arrow functions to move through the display.
  If you want the cursor to wrap to the opposite edge of the display, use one of the following function sequences:
  EXT + Right arrow
  EXT + Left arrow

INSERT

VT100: EXT + PF4	VT200: F14
DEFINE_KEY Function: INSERT_MODE

Enables insert mode. Use insert mode to edit what you entered. If the status display is enabled, Insert appears.

In insert mode, when you enter a character in to an unprotected field, it is displayed to the left of the cursor, moving the following one position to the right:

• The cursor
• The character at the cursor location
• All the characters to the right of the cursor in the field

You can insert characters in to an:

• Unformatted screen
• Unprotected field on a formatted screen until it is full

If you attempt to insert characters after the field is full, the keyboard locks, the terminal bell rings, and the word Inhib appears on the status line. If the keyboard locks when you try to insert characters in to a field that looks empty, the field might have trailing spaces. To erase these spaces, use the ER EOF function.

To return your screen to the normal mode of entry, use one of the following keyboard functions:

• RESET
• CLEAR
• ENTER
• Any PA key
• Any PF key

Logical NOT (| --)

VT100: EXT + N	VT200: EXT + N
DEFINE_KEY Function: (None)

Represents the remote host's symbol for a logical NOT; displayed as a circumflex ( ^ ) on DIGITAL terminals.

Logical OR (|)

VT100: EXT + O	VT200: EXT + O
DEFINE_KEY Function: (None)

Represents the remote host's symbol for a logical OR; displayed as a solid vertical line from the terminal's graphics set. Press Ext + O if the vertical bar is not available on your keyboard.

New Line (Hooked left arrow)

VT100: Return	VT200: Return
DEFINE_KEY Function: NEWLINE

Moves the cursor to the first unprotected position on the next line of your screen. If no unprotected fields are on the screen when you invoke the new line function, the cursor moves to the first location on the screen. If the screen has no fields, this key has the same function as the Return key on DIGITAL terminals.

NUM OVR (numeric lock override)

VT100: EXT + J	VT200: Remove
DEFINE_KEY Function: NUMOVR

Lets you enter nonnumeric characters in to numeric fields. Once you enable this function, use NUM OVR again to disable it. If you do not disable the numeric lock override, it remains enabled even after you exit from TN3270. The letter O appears on the status line to indicate that the numeric lock override is in effect.

PA1, PA2, PA3

VT100: PF4 , KP- , KP,	VT200: PF4 , KP- , KP,
DEFINE_KEY Function: PA1--PA3

These program access keys are defined by the program you are using. These keys request attention from the remote application program without sending any data. You should refer to the user's guide of your application program to learn how the PA keys are defined.

PF1 through PF24

VT100: see below	VT200: see below
DEFINE_KEY Function: PF1--PF24

These program function keys are defined by the remote application program you are using. They request attention from the application program and send the data entered to the host. The PF keys are coded by the application program to perform functions relating to the application. A particular PF key may be coded differently from one application to another. The user's guide of the remote application program usually defines the specific PF key assignments for that application program.

To Implement This Function	Press This Key or Key Combination
PF1	PF1
PF2	PF2
PF3	PF3
PF4	KP7
PF5	KP8
PF6	KP9
PF7	KP4
PF8	KP5
PF9	KP6
PF10	KP1
PF11	KP2
PF12	KP3
PF13	EXT + PF1
PF14	EXT + PF2
PF15	EXT + PF3
PF16	EXT + KP7
PF17	EXT + KP8
PF18	EXT + KP9
PF19	EXT + KP4
PF20	EXT + KP5
PF21	EXT + KP6
PF22	EXT + KP1
PF23	EXT + KP2
PF24	EXT + KP3