Page 52 - DCAP602_NETWORK_OPERATING_SYSTEMS_I

Network Operating Systems-I

notes

Task Analyse the uses of TERM variable.

2.4.2 communication (Dialing) programs

Dialing programs for making a PPP connection to the Internet don’t normally include any terminal
emulation. But some other modem dialing programs (such as minicom or seyon) do. Using them,
one may (for example) dial up some public libraries to use their catalogs and indexes, (or even
read magazine articles). They are also useful for testing modems. Seyon is only for use with X
Window and can emulate Tektronix 4014 terminals.
The communication program Kermit doesn’t do terminal emulation as it is merely a
semi-transparent pipe between whatever terminal you are on and the remote site you are
connected to. Thus if you use kermit on a Linux PC the terminal type will be “Linux”. If you have
a Wyse60 connected to your PC and run kermit on that, you will appear as a Wyse60 to the remote
computer (which may not be able to handle Wyse60 terminals). Minicom emulates a VT102 and
if you use it on Wyse60 terminal VT102 escape sequences coming into your computer’s serial
port from a remote computer will get translated to the Wyse escape sequences before going out
another serial port to your Wyse60 terminal. Kermit can’t do this sort of thing.
Emulators exist under DOS such as telix and procomm work just as well. The terminal emulated
is often the old VT100, VT102, or ANSI (like VT100).

emulation under x window

Xterm (or uxterm which is like xterm except it supports unicode) may be run under X Window.
They can emulate a VT102, VT220, or Tektronix 4014. There are also various xterm emulations
(although there is no physical terminal named “xterm”). If you want pixmaps but don’t need
the Tektronix 4014 emulation (a vector graphics terminal; see Graphics Terminals) you may use
eterm. Predecessors to eterm are rxvt and xvt. One way to change font size in xterm is to right
click the mouse while holding down the Ctrl key.
For non-Latin alphabets, kterm is for Kanji terminal emulation (or for other non-Latin alphabets)
while xcin is for Chinese. There is also 9term emulation. This seems to be more than just an
emulator as it has a built-in editor and scroll-bars. It was designed for Plan 9, a Unix-like operating
system from AT&T.

real terminals Better

Unless you are using X Window with a large display, a real terminal is often nicer to use than
emulating one. It usually has better resolution for text, and has no disk drives to make annoying
noises.

2.5 testing terminal emulation

For the VT series terminals there is a test program: vttest to help determine if a terminal
behaves correctly like a vt53, vt100, vt102, vt220, vt320, vt420 etc. There is no documentation but
it has menus and is easy to use. To compile it run the configure script and then type “make”. It
may be downloaded from: http://ibiblio.unc.edu/pub/Linux/utils/console/

46 LoveLy professionaL university