VMS Help PASCAL, Lexical Elements  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  A Pascal program  is  composed  entirely  of  lexical  elements.
  These  elements  are  individual  symbols,  such  as  arithmetic
  operators, or they may be words that have  special  meanings  in
  Pascal.   The  basic unit of any lexical element is a character,
  which must be a member of the ASCII character set.

  The  words  used  in  a  Pascal  program  are  combinations   of
  alphabetic and numeric characters and occasionally a dollar sign
  ($), an underscore (_), or a percent sign (%).  Some  words  are
  reserved for the names of executable statements, operations, and
  predefined data structures.  Other words in a Pascal program are
  identifiers.   Predeclared  identifiers  represent  routines and
  data types provided by Compaq  Pascal.   Other  identifiers  are
  created  by  the  use  to  name  programs,  symbolic  constants,
  variables, and any necessary  program  elements  that  have  not
  already been named.

1 - Character Set

  Compaq Pascal uses  the  extended  American  Standard  Code  for
  Information  Interchange (ASCII) character set.  The is extended
  ASCII character set contains 256 characters, which  include  the
  following:

   o  Uppercase letters  A  through  Z  and  lowercase  letters  a
      through z

   o  Integers 0 through 9

   o  Special characters, such as the ampersand (&), question mark
      (?), and equal sign (=)

   o  Nonprinting characters, such as the space, tab,  line  feed,
      carriage  return, and form feed (use of these characters may
      improve the legibility of your programs)

   o  Extended, unspecified characters with numeric codes from 128
      to 255

  The  Compaq  Pascal  compiler  does  not   distinguish   between
  uppercase  and  lowercase letters except when they appear inside
  apostrophes.

  For a complete listing of  the  ASCII  character  set,  see  the
  "Compaq Pascal Language Reference Manual."

2 - Special Symbols

  Special  symbols  represent  delimiters,  operators,  and  other
  syntactic  elements.  Some symbols are composed of more that one
  character; you cannot place a space between  the  characters  of
  these  special symbols.  Examples of special symbols include the
  apostrophe ('), the assignment operator (:=) and the  not  equal
  sign (<>).

3 - Reserved Words

  Reserved words are words that are  reserved  for  the  names  of
  statements,  data  types,  directives,  identifiers, specifiers,
  statements,  and   operators.    You   cannot   redefine   these
  identifiers.   Examples of reserved words include AND, END, NOT,
  IF, and WHILE.

  Redefinable reserved  words  are  used  to  name  operators  and
  identifiers.  You can redeclare these words, but, if you do, the
  language feature becomes unavailable within the block  in  which
  you  redeclare  the  word.   The  redefinable reserved words are
  AND_THEN, BREAK,  CONTINUE,  MODULE,  OR_ELSE,  OTHERWISE,  REM,
  RETURN, VALUE, and VARYING.

4 - Identifiers

  An identifier is a combination of letters, digits, dollar  signs
  ($),   and   underscores  (_)  that  conform  to  the  following
  restrictions:

   o  An identifier cannot start with a digit.

   o  An identifier cannot contain any space or special symbols.

   o  The first 31 characters must denote a unique name within the
      block  in  which  the identifier is declared.  An identifier
      longer than 31 characters generates a warning  message;  the
      compiler   ignores   characters   beyond   the  thirty-first
      character.  An  identifier  cannot  start  or  end  with  an
      underscore, nor can two adjacent

 4.1 - Predeclared Identifiers

  Predeclared identifiers name data types, symbolic constants  and
  file  variables,  procedures, and functions.  You can redefine a
  predeclared identifier, but, if you do, the original declaration
  becomes unavailable within the block in which you redeclared the
  word.  Examples of predeclared identifiers include ADDRESS, COS,
  ERR, INTEGER, SQR and TRUE.

 4.2 - User Defined Identifiers

  User identifiers denote the names of programs, modules, symbolic
  constants,  variables,  procedures, functions, program sections,
  and  user-defined  types.   They  represent   significant   data
  structures,  or  values  and actions that are not represented by
  reserved words, predeclared identifiers, or special symbols.