Many hosts use the ASCII (American Standard Code for Information Interchange) character set to simplify communication with other computers; for example, a Digital VAX running VMS, almost all UNIX systems, and Macintosh or PC-DOS systems. You can use either the VT102, VT100, or Heath-19 emulation with these hosts; the VAX requires the VT100 or VT102.
The buttons at the top of the window provide a convenient method of sending frequently used commands to the host with the mouse. You can also select text on the screen with the mouse to Copy, Paste, Append, or Print.
ASCII mode controls: On the left hand side, there are 12 buttons, which send key sequences equivalent to the Keypad keys in VT100 Application mode. By moving the mouse over the '?' at the left hand side you can see the labels for the buttons. Holding down the Shift key allows you to shift the buttons to send another 12 keys.
At the top of the emulator screen there are 11 buttons which perform functions useful with hosts which use ASCII terminals.
Key Function
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CR Enter a line of text or a command.
LF Send an ASCII Line Feed character.
ESC Send an ASCII Escape character.
CTL-S Stop transmission to your terminal.
CTL-Q Restart transmission to your terminal.
DEL Send an ASCII DEL character.
Break Send a break.
CTL-C Usually used to abort a command.
CTL-U Usually used to abort a command.
To the right of the buttons are two counters; the left one shows the packets sent to the network, the right one shows the packets received.
Moving the mouse over a point on the terminal screen will draw a heavy underline beneath that character position; pressing the mouse button will cause Comet to attempt to move the terminal cursor to the underlined position. (Cursor positioning can be disabled using the "!Ct" macro.) Please note that if you click again while the cursor is still moving, it will not move to the point you expect it to! If the cursor does not go to the proper position on the first mouse click, try it again; the presence of tabs in the text may cause incorrect positioning. When using the UNIX vi editor, you can use "vi cursor motion" to get around this problem, in addition to speeding the process up. ("vi cursor motion" does have a minor problem in that it does not handle wrapped lines properly.)
You can modify ASCII key mapping using options in the "Control Window" dialog; the default keymapping has:
` -> Escape
Backspace -> Delete
Use the Heath-19 emulator and turn on the "Use IBM menus and key mapping" option in the "Control Emulator..." dialog if you want to communicate with an IBM mainframe through the 7171 ASCII terminal adapter. This mode allows you to run programs such as the XEDIT full-screen editor as if you were using an IBM 3278 terminal. Buttons and menu items are provided which allow you to conveniently produce the commands the 7171 accepts as the equivalent of keys on the 3278 terminal. When the 7171 requests your terminal type, type in "C19".
