A class resembles the C++ class. That is it consists of a collection of data and methods (C++ Member Functions). Code using an itcl class may have multiple instances of a class (there may be several different people with several bank accounts each - a person and a bank account would be 2 sensible classes to define). package require Itcl itcl::class helloworld { public variable owner "No-one" method greet {} { puts "Hello World from $owner" } } helloworld h1 helloworld h2 h1 greet h1 configure -owner Me h2 configure -owner You h1 greet h2 greet Creates 2 helloworld objects (h1 & h2). By default they respond with the name "No-One" when the method greet is called. You can set public variables of the class using the configure command as above; variables are private by default (but can also be of type 'protected'). Private variables often employ code like this: package require Itcl itcl::class helloworld { private variable owner "No-one" method setowner {nuowner} { set owner $nuowner} method getowner { } { return $owner } method greet {} { puts "Hello World from $owner" } } helloworld h1 helloworld h2 h1 setowner Me h2 setowner You h1 greet h2 greet The class can also have a constructor & destructor method, and can refer to itself by the $this variable. package require Itcl itcl::class helloworld { public variable owner "No-one" constructor {} {puts "helloworld object $this has been created"} destructor { puts "$this is deleted - you should delete any dynamically allocated items here"} method greet {} { puts "Hello World from $owner" } } helloworld h1 h1 greet itcl::delete object h1 h1 greet ;# will return an error "invalid command name "h1"" since h1 has been deleted. Well that is a basic guide to classes. More to follow! [Derived itcl::class][GWM]