Lexical_Elements

 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  VSI  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.

Additional information available:

Character_Set   Special_Symbols Reserved_Words  Identifiers