Integer Literals

Integer literals may be expressed in a variety of formats. The sections below describe the rules for each format and provide examples.

Decimal (base 10)

Rules

  • Cannot start with 0 (except for 0 itself), that would make it octal.
  • Cannot include a decimal point - that would make it floating point, even if the fractional part is 0.
  • Cannot include commas or spaces.
  • Must use only the digits zero-nine.
  • May be preceded by a minus sign "-".

Examples of Valid Decimal Integers

0 5 127 -1021 65535

Examples of Invalid Decimal Integers

32,767 25.0 1 024 0552 7A

Hexadecimal (base 16)

Rules

  • Must begin with 0x or 0X.
  • May use digits zero-nine and the letters A-F or a-f (not case sensitive).
  • Cannot include a decimal point.
  • Cannot include commas or spaces.
  • May be preceded by a minus sign "-".

Examples of Valid Hexadecimal Integers

0x 0x1 0x0A2B 0x12 0xBEEF

Yes, 0x is legal and represents a value of 0. However, nobody uses 0x alone, except perhaps in The International Obfuscated C Code Contest.

Examples of Invalid Hexadecimal Integers

0x5.3 0EA12 0xEG 53h

Octal (base 8)

While octal is still part of the ANSI/ISO C specification, almost no one uses it anymore.

Rules

  • Must begin with 0.
  • Must use only the digits zero-seven.
  • Cannot include a decimal point.
  • Cannot include commas or spaces.
  • May be preceded by a minus sign "-".

Examples of Valid Octal Integers

01 012 073125

Examples of Invalid Octal Integers

05.3 0o12 080 53o

Binary (base 2)

​

ANSI C does not specify a format for binary integer literals. However, this quasi-standard notation is supported by many compilers for embedded microcontrollers. If your code must be ANSI compliant, do not use this notation.

Rules

  • Must begin with 0b or 0B.
  • Must use only the digits zero-one.
  • Cannot include a decimal point.
  • Cannot include commas or spaces.
  • May be preceded by a minus sign "-".

Examples of Valid Binary Integers

0b 0b1 0b0101001100001111

Examples of Invalid Binary Integers

0b1.0 01100 0b12 10b

  Return to Top

© 2024 Microchip Technology, Inc.
Notice: ARM and Cortex are the registered trademarks of ARM Limited in the EU and other countries.
Information contained on this site regarding device applications and the like is provided only for your convenience and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications. MICROCHIP MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY OR OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE, MERCHANTABILITY OR FITNESS FOR PURPOSE. Microchip disclaims all liability arising from this information and its use. Use of Microchip devices in life support and/or safety applications is entirely at the buyer's risk, and the buyer agrees to defend, indemnify and hold harmless Microchip from any and all damages, claims, suits, or expenses resulting from such use. No licenses are conveyed, implicitly or otherwise, under any Microchip intellectual property rights.