KEYWORDS

• The keywords are reserved for specific meanings in C language

• C has nearly 32 keyword

• Keywords, combined with the formal C syntax, forms the C programming language

• The variables should not be named with any of the keywords as the meanings cannot be changed

• All the keywords are lower case letters

• Keywords are also called as reserved words

• All the keywords have pre-defined meanings

auto	double	int	struct
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

• auto

• auto is used to define a variable of storage class automatic. 

• Variables declared within function bodies are automatic by default. 

• They are recreated each time a function is executed. 

• Since, automatic variables are local to a function, automatic variables are also called local variables.

• break and continue

• The break statement is used to jump out of the innermost enclosing loop (while, do, for or switch statements) explicitly and pass control to next statement immediately following the loop. 

• In other hand, continue statement is used to skip certain statements inside the loop.

• switch, case and default 

• The switch statement tests the value of a expression and test with the different "case" values. 

• We can use "default" value, if it doesn't matches any of "case" values. 

• char

• The char keyword is used for indicating the variable is of the type character. 

• const 

• const makes the value of a pointer or a variable unmodifiable. 

• This value cannot be changed in program.

• do and while 

• while and do are used for looping in C. 

• double and float

• double and float are used for indicating floating type variables. 

• Keywords float and double represents single precision and double precision floating point data respectively. 

• if and else 

• if and else are used in decision making in C.

• enum : 

• enum is used to define enumerated type data type. 

• Enumerated data type creates a set of constant of type int. 

• extern

• Keyword extern is used for indicating the variable is external 

• It is declared outside every function and can be accessed by any function. 

• for 

• Keyword for is used for looping in C. 

• goto 

• Keyword goto is used for unconditional jump to a labeled statement inside that function. 

• int 

•  int is used for indicating the variable is of type integer.

• short, long, signed and unsigned : 

• short, long, signed and unsigned are type modifiers that alters the meaning of base data type to yield new type.

• return 

• Keyword return terminates the execution of current function and returns the value to the calling function

• sizeof 

• sizeof is used to find the number of bytes of an object.

• register 

• Variable of storage class register are much faster than normal variables

• static 

• static is used for indicating the variable is of storage class static. 

• The value of the static variables persists until the end of the program. 

• struct 

• struct is used in creating a structure which provide means to group different types of variable under one name for easier handling.

• typedef 

• Keyword typedef is used to explicitly associate a type with an identifier.

• union

• Union is used in creating a union which provide means to group different types of variable under one name for easier handling.

• void 

• void is used to indicate that a function takes no arguments or returns no value.

• volatile 

• volatile is used to create a volatile object. 

• A volatile object can be modified in unspecified way by the hardware.