Re: documents, files, types, and access methods

Brent Welch (
Fri, 6 Dec 1991 09:46:19 PST

Message-Id: <>
Date:   Fri, 6 Dec 1991 09:46:19 PST
From: Brent Welch <>
Subject: Re: documents, files, types, and access methods
In-Reply-To: <>

The model that TCL has it that each tool has an embedded TCL
interpreter, and tools can issue commands to each other in the TCL
language.  TCL is designed to be simple for simple things, and it is
fully programmable.  TCL provides basic language features, and the
application that embeds an interpreter can define new commands, either
as C procedures or as TCL command procedures (scripts).  For example,
the Tk X toolkit defines a number of TCL commands to create widgets, so
it is possible to write window programs with a script.  Since each
window (ideally) has a TCL interpreter behind it, you can control your
tools by sending around TCL commands.  This is a more powerful
alternative to using mail header formats for messages. You can send
whole programs, not just commands.  The way I use this currently is to
couple a control panel with a shell window.  The control panel is put
together as a TCL/Tk script that uses the Tk toolkit to display buttons,
etc.  Clicking on buttons in the control panel can cause messages to be
sent to the terminal emulator (tx).  One very useful command passes a
string along to the shell running in the terminal emulator.  In this way
I can create buttons that run commonly used programs.  Other commands
control the terminal emulator itself, such as its size and placement on
the screen, the message in its status line, etc.  The whole model of a
bunch of tools that have a common language and can fire off commands to
each other is very powerful.

        Brent Welch