C Numeric Constants

C numeric constants can be any of the following:

• Decimal integer constants (base 10) consist of one or more digits, 0 through 9, where 0 cannot be used as the first digit.

• Binary constants (base 2) begin with a 0b or 0B prefix, followed by one or more binary digits (0, 1).

• Octal constants (base 8) consist of one or more digits 0 through 7, where the first digit is 0.

• Hexadecimal constants (base 16) begin with a 0x or 0X prefix, followed by a hexadecimal number represented by a combination of digits 0 through 9, and characters A through F.

• Floating-point constants consist of:

        — an optional sign             - or +

        — an integer part              a combination of digits 0 through 9

        — a period                         .

        — a fractional part            a sequence of digits 0 through 9

        — an optional exponent    e or E, followed by an optionally signed sequence of one or more digits

For example, the following floating-point constant contains both the optional and required parts: +1.15e-12.

The following floating-point constant contains only the required parts: 1.0

The following formal grammar summarizes the rules for the C numeric constants:

C-constant:

  C-integer-constant
  floating-point-constant
  character-constant

C-integer-constant:

  [1-9][0-9]*
  0[bB][01]*
  0[0-7]*
  0[xX][0-9a-fA-F]*

floating-point-constant:
  integer-part.[ fractional-part ] [ exponent-part ]

integer-part:
  [0-9]*

fractional-part:
  [0-9]*

exponent-part:
  [eE][+-][0-9]*
  [eE][0-9]*