Difference between Keyword and Identifier in C (original) (raw)

Last Updated : 10 Jun, 2026

Keywords and Identifiers are the basic building blocks of a C program. Keywords are reserved words with predefined meanings, while identifiers are user-defined names used to identify program elements.

Keywords define the syntax and structure of the C language and cannot be used as names.
Identifiers are user-defined names given to variables, functions, arrays, structures, and other program elements.

Keyword

A keyword is a reserved word in C that has a special meaning predefined by the compiler. Keywords are part of the language syntax and cannot be used as identifiers.

Keywords have predefined meanings in the C language.
They cannot be used as variable, function, or class names.

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

Identifier

An identifier is a user-defined name used to identify variables, functions, arrays, structures, and other program elements. Identifiers help programmers give meaningful names to entities in a program.

Identifiers are created by programmers.
They must follow C naming rules and conventions.

**Example:

studentName
calculateSum
age
totalMarks
employee_id

Keyword Vs Identifier

Feature	Keyword	Identifier
Definition	A reserved word with a predefined meaning in C.	A user-defined name used to identify program elements.
Purpose	Defines the syntax and structure of the language.	Names variables, functions, arrays, structures, etc.
Defined By	C Language	Programmer
Can Be Modified	No	Yes
Usage as Variable Name	Not Allowed	Allowed
Meaning	Fixed and predefined.	Depends on the programmer's choice.
Number Available	Limited and predefined.	Unlimited (within naming rules).
Examples	int, if, while, return	age, salary, display(), studentName