C Keywords & Identifiers

Updated on January 8, 2026

2 min read

C Keywords

Keywords are reserved words in C that have a fixed meaning.

They cannot be used as variable names, function names, or identifiers.

C has 32 keywords.

S No.	Keyword	Purpose
1	auto	Declares automatic variable
2	break	Exits a loop or switch
3	case	Specifies a branch in switch
4	char	Character data type
5	const	Makes variable constant
6	continue	Skips current loop iteration
7	default	Default case in switch
8	do	Starts do-while loop
9	double	Double precision floating type
10	else	Executes when if condition is false
11	enum	Defines enumeration
12	extern	Declares external variable
13	float	Floating point data type
14	for	Looping statement
15	goto	Transfers control
16	if	Conditional statement
17	int	Integer data type
18	long	Long data type modifier
19	register	Stores variable in CPU register
20	return	Returns value from function
21	short	Short data type modifier
22	signed	Signed data type
23	sizeof	Finds size of data type
24	static	Retains value between calls
25	struct	Defines structure
26	switch	Multi-way decision
27	typedef	Creates type alias
28	union	Defines union
29	unsigned	Unsigned data type
30	void	No return type
31	volatile	Prevents optimization
32	while	Looping statement

int age;      // int is a keyword
return 0;    // return is a keyword

Identifiers are names given by the programmer to variables, functions, arrays, etc.

int total;
float marks;
int _count;

int 1num;     // starts with number
int total-marks; // special character
int int;      // keyword used

Keyword	Identifier
Reserved word	User-defined name
Fixed meaning	Meaning decided by programmer
Cannot be changed	Can be changed
Example: int	Example: age