Put the .el file into a directory in your LoadPath and add the following to your ~/.emacs file:
(autoload 'tacl-mode "tacl-mode" "A major mode for editing TACL files." t nil)
When you are visiting a TACL macro file, use ‘M-x tacl-mode’ to activate the mode.
For best performance you should byte compile .el files but it’s not required. A CompiledFile usually runs faster. There should be no warnings when compiling this file.
See TandemNskSupport for a method of automatically recognizing the language of Tandem files since they don’t have an extension and coders often can’t stick a -*-tacl-*- comment in line 1.
If you are unfamiliar with this site, you can get files from the ElispArea.
By default tacl-mode looks for a file named tacl-syntax.el which is expected to contain help string definitions. You can customize tacl-eldoc-def-files to look for a different file or even a list of files. The one I’ve uploaded contains around 750 doc strings I hope you find useful. Files on the tacl-eldoc-def-files list need only be somewhere on your LoadPath to be found.