5.4 Program Documentation
  Documenting a program is the process of mixing text (com-
  ments) and code in a way that helps make the program more
  understandable. Program documentation does not affect the
  way a program executes.

  You can add comments throughout a program; however,
  programs that are neatly structured need fewer comments.
  You can clarify your code by doing the following:

  .
        Using meaningful variable names
  .
        Including sufficient white space
  .
        Indenting your program lines according to the structure
        of your code

  A comment field starts with an exclamation point ( ! ) and
  ends with a carriage return. The following example con-
  tains both comments and program statements. Any text that
  follows an exclamation point is ignored.
  PROGRAM sample
  !+
  ! Require that all variables be declared
  !-
  OPTION TYPE = EXPLICIT
  !+
  ! Set up error handler
  !-
  WHEN ERROR USE Error_routine
  !+
  ! Declarations
  !-
      .
      .
      .
  END PROGRAM

  You can also mix comments and code on the same line. For
  example:
  DECLARE &
        INTEGER &
        Print_page, ! Current page number &
        Print_line, ! Current line number &
        Print_column ! Current column number

  All text between the exclamation point and the carriage re-
  turn is ignored, with one exception: the ampersand is still
  recognized. This is a continuation character that specifies
  that a single statement is being continued on the next line.
  Only spaces and tabs are valid between the ampersand and
  the carriage return.