info gdb

No value for GDBN 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 section C and C++ Constants, for a brief explanation of escape sequences.
Enumerated constants consist of an enumerated identifier.
Boolean constants consist of the identifiers TRUE and FALSE.
Pointer constants consist of integral values only.
Set constants are not yet supported.