An ASCII text file (with the extension .tcl) that contains importable Tcl code or an executable Tcl script.

Tcl, an abbreviation of the name "Tool Command Language", is a scripting language for controlling and extending software applications. A .tcl file contains a Tcl script, which is composed of Tcl functions and can also include Quartus II Application Programming Interface (API) functions used as commands.

You can run Tcl scripts at a command line, in the Quartus II Tcl Console window, with the Tcl Scripts command on the Tools menu, or as tasks in the Tasks window.