C Keyword & Identifiers


Keywords are reserved words whose meaning is predefined by the programming language specification. They convey some special meaning in programming and we must not use them for other purposes.

Rules for defining a keyword are:

  • Those words whose meaning already defined by the compiler.
  • Cannot be used as Variable Name.
  • There are 32 Keywords in C.
  • C Keywords are also called as Reserved words.

32 Keyword in the C Programming language:

auto double intstruct
break else long switch
case enum register typedef
char extern return union
const float short unsigned
continue for signed void
default goto sizeof volatile
do if static while


Identifiers refers to name given to entities such as variables, functions, structures etc.Identifiers must be unique. They are created to give a unique name to an entity to identify it during the execution of the program.

Rules for naming identifiers

  • Identifiers are case-sensitive.
  • You cannot use keywords as identifiers.
  • The first character must be an alphabet or underscore.
  • Must not contain white spaces.

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