-II- What is Tcl? Tk? Extended Tcl?

From: FAQ General information

	Tcl and Tk originated with Dr. John Ousterhout (Oh'-stir-hout -
last syllable rhymes with rout, not root) from the University of California,
Berkeley, California.

	Tcl (current release version 7.3) stands for ``tool command
language'' and is pronounced ``tickle.'' The author's home ftp site for
the Tcl source code is ftp.cs.berkeley.edu.  Tcl is actually two
things: a language and a library.  First, Tcl is a simple textual
language, intended primarily for issuing commands to interactive
programs such as text editors, debuggers, illustrators, and shells.  It
has a simple syntax and is also programmable, so Tcl users can write
command procedures to provide more powerful commands than those in the
built-in set.

	Second, Tcl is a library package that can be embedded in
application programs.  The Tcl library consists of a parser for the Tcl
language, routines to implement the Tcl built-in commands, and
procedures that allow each application to extend Tcl with additional
commands specific to that application.  The application program
generates Tcl commands and passes them to the Tcl parser for
execution.  Commands may be generated by reading characters from an
input source, or by associating command strings with elements of the
application's user interface, such as menu entries, buttons, or
keystrokes.  When the Tcl library receives commands it parses them into
component fields and executes built-in commands directly.  For commands
implemented by the application, Tcl calls back to the application to
execute the commands.  In many cases commands will invoke recursive
invocations of the Tcl interpreter by passing in additional strings to
execute (procedures, looping commands, and conditional commands all
work in this way).

	An application program gains three advantages by using Tcl for
its command language.  First, Tcl provides a standard syntax:  once
users know Tcl, they will be able to issue commands easily to any
Tcl-based application.  Second, Tcl provides programmability.  All a
Tcl application needs to do is to implement a few application-specific
low-level commands.  Tcl provides many utility commands plus a general
programming interface for building up complex command procedures.  By
using Tcl, applications need not re-implement these features.  Third,
extensions to Tcl, such as the Tk toolkit, provide mechanisms for
communicating between applications by sending Tcl commands back and
forth.  The common Tcl language framework makes it easier for
applications to communicate with one another.

	Tk (current release 3.6) - an extension to Tcl which provides
the programmer with an interface to the X11 windowing system.  The
author's home ftp site for the Tk source is ftp.cs.berkeley.edu.
Note that many users will encounter Tk via the ``wish'' command.  Wish
is a simple windowing shell which permits the user to write Tcl
applications in a prototyping environment.

	Extended Tcl (tclX) (Version 7.3a) - This is an extended set of
commands for Tcl developed by Karl Lehenbauer and Mark Diekhans.  The
authors' home ftp site for Extended Tcl is ftp.neosoft.com.  Extended
Tcl is oriented towards system programming tasks, with many additional
interfaces to the Unix operating system along with other useful
utilities.