15.4.9.3 Constants
GDB allows you to express the constants of Modula-2 in the following
ways:
-  Integer constants are simply a sequence of digits.  When used in an
expression, a constant is interpreted to be type-compatible with the
rest of the expression.  Hexadecimal integers are specified by a
trailing ‘H’, and octal integers by a trailing ‘B’.
-  Floating point constants appear as a sequence of digits, followed by a
decimal point and another sequence of digits.  An optional exponent can
then be specified, in the form ‘E[+|-]nnn’, where
‘[+|-]nnn’ is the desired exponent.  All of the
digits of the floating point constant must be valid decimal (base 10)
digits.
-  Character constants consist of a single character enclosed by a pair of
like quotes, either single (') or double (").  They may
also be expressed by their ordinal value (their ASCII value, usually)
followed by a ‘C’.
-  String constants consist of a sequence of characters enclosed by a
pair of like quotes, either single (') or double (").
Escape sequences in the style of C are also allowed.  See C and C++ Constants, for a brief explanation of escape
sequences.
-  Enumerated constants consist of an enumerated identifier.
-  Boolean constants consist of the identifiers TRUEandFALSE.
-  Pointer constants consist of integral values only.
-  Set constants are not yet supported.