An identifier is a name given to a program element such as a variable, function, or array. This name may be used to refer to the program element without knowing its specific location in memory.

Identifiers in C must be strings of characters from the valid C character set, which includes all the letters of the English alphabet (both upper and lower case), the numbers 0-9, and the underscore. The first character of an identifier must NOT be a number and under no circumstances may an identifier contain a space.


All identifiers are case sensitive, so you can have two identical identifiers except for the case of the first character and they will be considered two completely different identifiers.

Also, according to the ANSI C standard, only the first 31 characters of an identifier are significant. So, if you had two 32 character identifiers differing only in the last character, some compilers would not recognize them as being different. With that said, most modern compilers far exceed the limit of 31 characters, allowing very long identifiers with many more significant characters.

20th Annual
Microchip MASTERs Conference 2016
Register now - Deadline: July 29

JW Marriott Desert Ridge Resort-Phoenix, AZ

© 2016 Microchip Technology, Inc.
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contained on this site regarding device applications and the like is provided only for your convenience and may be superseded by updates.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.