Language file created for Forth programming language, which is supported by several different text editors that enable features such as syntax highlighting; contains Forth programming code similar to how .C files contain C or C++ source code; same format as the .FORTH file.
Forth language's format is based on data stack and RPN (Revers Polish Notation). A simple example of its format:
12 10 * 40 + .
This format equals to 12 multiplied by 10 plus 40, with "." printing the result of the mathematical equation to the user terminal.
NOTE: To create a 4TH file simply rename the extension of your plain text file that contains the Forth source code.