Conditional Compilation Directives 

                              Conditional Symbols 

     The use of conditional compilation directives will enable you to
     compile different segments of your source code based on Conditional
     Symbols.  There are four standard symbols in Turbo Pascal; they are:

          VER55  Defined by the Turbo Pascal based on the version
                 number of the compiler in use.  Origniating with
                 version 4.0 and defined as VER40 and so forth.

          MSDOS  Inidicates the operating system.  Other versions of
                 Turbo Pascal for another O/S will have a symbolic
                 name for that operating system.

          CPU86  Indicates the CPU belongs to the 80x86 family.  Other
                 versions of Turbo Pascal for another CPU family will
                 have a symbolic name for that CPU family.

          CPU87  Defined at compile time only if an 80x87 is found.

     Conditional symbols follow the same rules as identifiers.  Their name
     must start with a letter and can be of any length, but only the first
     63 characters are significant.

     Conditional symbols act similar to boolean varaiables.  They are
     either defined (True) or undefined (False).

                            Conditional Directives 

     The conditional directives control compilation of segments of your
     source code.  This enables you to produce different code using the
     same program source.  The conditional directives are:

  {$DEFINE name}      Defines a conditional symbol with the given name
  {$UNDEF name}       Undefines a conditional symbol with the given name
  {$IFDEF name}       Compile following source if symbol is defined
  {$IFNDEF name}      Compile following source if symbol is not defined
  {$IFOPT switch}     Compile following source if switch is is in the
                      specified state
  {$ELSE}             Switches between compiling/ignoring source contained
                      within the {$IFxxx} and the next {$ENDIF} directives
  {$ENDIF}            Terminates the conditional compile started by the
                      last {$IFxxx} directive