Tcl

Tcl (pronounced "tickle" or tee cee ell /ˈtiː siː ɛl/) or Tool Command Language is a High-level programming language which can be used for many things. Tcl was made to be easy to use, but able to do many things.^[5] Tcl's language is based on commands which tell the computer what to do or how to save a variable. Tcl is able to do object-oriented, imperative, functional, or procedural styles.

Tcl

Paradigm	multi-paradigm: object-oriented, functional, procedural, event-driven programming, imperative
Designed by	John Ousterhout
Developer	Tcl Core Team
First appeared	1988; 37 years ago (1988)
Stable release	8.6.8 (Dec, 22 2017) / December 22, 2017; 7 years ago (2017-12-22)
Typing discipline	dynamic typing, everything can be treated as a string
License	BSD-style[1]
Filename extensions	.tcl, .tbc[2]
Website	www.tcl.tk
Major implementations
ActiveTcl Androwish
Dialects
Jim
Influenced by
AWK, Lisp
Influenced
PHP,[3] Tea, PowerShell[4]

Tcl is used a lot to in C to create prototypes quickly.^[6] There are interpreters available for many operating systems. This means many different kinds of computers are able to run Tcl code. Tcl is a very small language which means it is good to use as embedded systems.

Tcl is sometimes combined with Tk. When it is, it is called Tcl/Tk. Tcl/Tk is a part of the normal Python installation.

History

Tcl was created by John Ousterhout at University of California, Berkeley.^[7][8] Ousterhout won a ACM Software System Award in 1997 for making Tcl/Tk.^[9]

Safe-Tcl is a form of Tcl that has certain parts turned off so it can't hurt the computer which is running it. Nathaniel Borenstein and Marshall Rose created Safe-Tcl. Safe-Tcl can only work on some files including email messages.

Examples

In Tcl programming, empty whitespace separates words. Commands are ended by going to a new line or a semicolon:

word0 word1 word2 ... wordN

The first word is always a command which comes from Tcl's library:

commandName arg1 arg2 ... argN

For example, the commmand puts makes the computer display something:

puts "Hello, World!"

In that example, "Hello, World!" is called a string. Tcl adds a special character which can't be seen at the end of a line. This character tells the computer to go a new line after the command is complete.

Tcl is able to do math and many other things using variables. In order to use a variable, the programmer must set their value:

set variableA 1
set variableB 2

After a variable is set, it can be used in other parts of the program or set to something different. Variables can be used to perform math:

set x 2
set y 4
set ans [expr $x+$y]
puts "The answer is $ans." # The computer would show: "The answer is 6."

The command expr tells the computer to solve the "expression" or, in this case, an equation.

Easy commands

• set saves numbers, words, or letters, to a variable. It can also be used to change what is in a variable.
• proc tells the computer what a new command will do (procedure).
• if tells the computer to do what is written only if something is true.
• while tells the computer to do what is written as long as something is true.
• foreach tells the computer to something for each item in a list of variables.
• break stops the command from running. This is good to use to get out of a loop.
• continue stops the active command, but allows the loop to continue. If the loop is a while loop, it will start over. It will let foreach and for go to the next step in the program.
• return stops the active command and loop, then goes back to the procedure with a value.

Related pages

• Eggdrop
• TclX
• List of programming languages