LSE allows you to use  its  knowledge  of  programming  languages  to
  develop software.  LSE also allows you to design your own languages.

  In addition to programming languages, you can  define  languages  for
  other  things,  such  as  memos  or letters.  Once you have defined a
  language, you can save it in an environment file and  recall  it  for
  subsequent editing and update sessions.

  To create a new language, you first  create  a  source  file  (.LSE),
  within  LSE,  into  which  you  put  the LSE commands that define the
  elements of your language.  Once the source file  is  completed,  use
  the DO command to process the definitions.  You may then use the SAVE
  ENVIRONMENT command to  save  the  definitions  in  binary  form  for
  subsequent  use  by  LSE.   For  example,  to create a file for a new
  language, you do the following:

          1. Create a source file in an empty buffer, with a .LSE
             extension.

          2. Put all language, token, and placeholder definitions
             in the source file.

          3. Execute the commands in the source file by executing
             a DO command (to load the definitions for the current
             editing session).

          4. Execute a SAVE ENVIRONMENT command to save your new
             language definitions in a binary file (.ENV), for
             subsequent use.

  Thus, to create a binary image file (.ENV) for your language, you use
  the following sequence of commands:

             LSE> DO
             LSE> SAVE ENVIRONMENT filename
             LSE> EXIT