Emacs

Arguably the most powerful text editor in the world.

• Free
• Completely programmable
• Supports automatic FTP of files to/from Tandem/Guardian/NSK systems.
• Supports over 100 languages including many Legacy Tandem languages such as TACL, TAL/pTAL, Tandem Cobol85, Scobol, DDL and Enform.
• Runs on an always growing list of over 50 platforms.

Some useful links:

Official home page for Emacs

Home page for Emacs Tandem Support

Online support newsgroup at gnu.emacs.help