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DEFINE ('character' HersheyIdNumber) | ((expression))

 The DEFINE command may be used  to define a text character  assignment,
 or to  define  scalar and/or  vector  variables within  the  expression
 parsing system.

 In  the  first  case,   'character'  represents  the  symbol   numbered
 HersheyIdNumber in the font library.  When that character appears in  a
 string drawn by the  TEXT command, the specified  symbol will be  drawn
 instead  of  the  usual  symbol   attached  to  that  character.    The
 redefinition of the character applies  only to the current font.   This
 may be used to access Hershey characters which are not attached to  any
 characters   in    the   selected    fonts.    The    later    sections
 ALPHABETICAL-CHARACTER-INDEX  and   NUMERICAL-CHARACTER-INDEX   provide
 cross-references of the Hershey special characters.

 When a  parenthesized  expression follows  the  DEFINE command,  it  is
 collected and passed directly to the expression parser for  evaluation.
 Any numerical values  returned for  it are simply  ignored.  Since  the
 expression parser is quite  powerful and supports  a symbol table,  the
 expressions may assign scalar or  vector values to variables which  may
 subsequently  be  used  throughout  SLIDES  wherever  a   parenthesized
 expression is  permitted,  which  is  anywhere  a  numerical  value  is
 expected.