Tcl - a true interpretive, command based language
Tcl is a very different language to the others that I give courses on - it's a truly interpretive language who's structure is based on commands rather than operators and operands. Thank sounds a bit technical - so what does it really mean?
A Truly Interpretive language
is interpreted each step along the way. You'll often be told that Perl, Python or Lua is interpreted but that's not really the case - they are "compile and run" languages where the source code is checked once, and an intermediate "Byte code" produced - a slower start to running a program with all that extra work to do ahead of time, but once it's running much faster as the lexical analyzer doesn't have to go "p-r-i-n-t ... oh that's a print" every time around a loop.
And a Command Based Language
is one where every instruction starts
with a command word - it means that code such as
h = 12
isn't valid because that would be looking for a command called "h" with two parameters - an = sign and the string "1-2". This makes the source a little longer and clunkier, but the interpreter far smaller, and much easier for traditional engineers who only do a bit of programming to understand.
So really Tcl is very much closer to Shell Programming
than the other so-called scripting languages. Not a problem to us - we cover Shell Programming in Bash
briefly on our Linux basics
course (and much more on private courses), and Korn Shell Programming
on private courses
Footnotes - see here
for details of Lua's compiler, and here
to read more about how Python does it. Perl's byte code is discussed here
, and Java's is widely used - it's the "class file" - and you'll find mentions all over our site - see here
for example. (written 2009-10-20)
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articlesT201 - Tcl/Tk - What is Tcl? 
Still teaching Tcl in 2016? - (2016-01-06) 
Changes in advertising cut lines / Buscot / Tcl course - (2007-07-16) 
Installing Tcl and Expect on Solaris 10 - a checklist - (2007-05-02) 
Testing you Perl / PHP / MySQL / Tcl knowledge - (2006-04-19) 
Central London Courses - Perl, PHP, Python, Tcl, MySQL - (2005-07-18) 
Tcl embeds - (2004-11-28)
Some other Articles
Tcl - catching an error before your program crashesTcl - passing arrays and strings in and back out of procsMelksham Town - asleep or awake?Beauty in picturesTcl - a true interpretive, command based languagePython - how it saves on compile timeLuac - getting lua to start fast by precompilingMothers Day or Mothering Sunday?New Web Site for Melksham Chamber of CommerceCant connect to local MySQL server through socket /tmp/mysql.sock
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