All C Language Keywords Explained with Examples

Keyword	C Standard	Easy Description	Example / Usage
auto	C90	Default local variable inside a function	auto int x = 10;
break	C90	Immediately stops loop or switch	if(i==5) break;
case	C90	A matching option in switch	case 1: printf("One");
char	C90	Stores a single character	char ch = 'A';
const	C90	Value cannot be changed	const int x = 10;
continue	C90	Skips current loop step	if(i==3) continue;
default	C90	Runs if no case matches	default: printf("Invalid");
do	C90	Loop runs at least once	do{ i++; }while(i<5);
double	C90	Stores large decimal values	double d = 5.25;
else	C90	Runs when `if` is false	else printf("No");
enum	C90	Creates named integer constants	enum Day {MON,TUE};
extern	C90	Uses global variable from another file	extern int x;
float	C90	Stores decimal numbers	float f = 3.14;
for	C90	Loop with initialization and counter	for(i=0;i<5;i++)
goto	C90	Jumps to a labeled statement	goto label;
if	C90	Executes when condition is true	if(x>0)
int	C90	Stores whole numbers	int a = 10;
long	C90	Stores larger integers	long int x;
register	C90	Suggests faster memory access	register int i;
return	C90	Sends value back from function	return 0;
short	C90	Stores smaller integers	short int s;
signed	C90	Allows positive and negative values	signed int x;
sizeof	C90	Finds size of variable/type	sizeof(int)
static	C90	Retains value between function calls	static int count;
struct	C90	Groups different data types	struct Student {int id;};
switch	C90	Multiple condition selection	switch(choice)
typedef	C90	Creates new name for data type	typedef int INT;
union	C90	Shares memory for all members	union Data {int i;};
unsigned	C90	Stores only positive values	unsigned int x;
void	C90	No value or return type	void show()
volatile	C90	Value can change anytime	volatile int flag;
while	C90	Loop runs while condition is true	while(i<5)
inline	C99	Suggests faster function execution	inline int add()
_Bool	C99	Stores true or false	_Bool flag = 1;
_Complex	C99	Stores complex numbers	_Complex float z;
_Imaginary	C99	Stores imaginary numbers	_Imaginary float y;
restrict	C99	Improves pointer performance	int *restrict p;
_Alignas	C11	Sets memory alignment	_Alignas(16) int x;
_Alignof	C11	Gets alignment size	_Alignof(int)
_Atomic	C11	Ensures safe shared access	_Atomic int count;
_Generic	C11	Selects code by data type	_Generic(x,int:1)
_Noreturn	C11	Function never returns	_Noreturn void exit()
_Static_assert	C11	Compile-time condition check	_Static_assert(1,"OK");
_Thread_local	C11	Separate variable for each thread	_Thread_local int x;

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