C Programming Language Keywords

Data Types

• int - Integer data type
• char - Character data type
• float - Single-precision floating-point
• double - Double-precision floating-point
• void - Empty data type/no return value
• _Bool - Boolean data type (C99)
• long - Long integer data type
• short - Short integer data type
• signed - Signed modifier
• unsigned - Unsigned modifier

Storage Classes

• auto - Automatic storage duration
• register - Register storage class
• static - Static storage duration
• extern - External linkage

Control Flow

• if - Conditional statement
• else - Alternative branch in conditional
• switch - Multi-way decision
• case - Label in switch statement
• default - Default label in switch
• break - Exit from loop/switch
• continue - Skip to next iteration
• return - Return from function
• goto - Jump to label

Loops

• for - For loop
• while - While loop
• do - Do-while loop

Type Qualifiers

• const - Constant value
• volatile - Value may change unexpectedly
• restrict - Pointer optimization hint (C99)

Structure and Union

• struct - Structure declaration
• union - Union declaration
• typedef - Create type alias
• enum - Enumeration declaration

Size and Alignment

• sizeof - Size of type/variable
• _Alignas - Specify alignment (C11)
• _Alignof - Query alignment (C11)

Complex Numbers (C99)

• _Complex - Complex number type
• _Imaginary - Imaginary number type

Atomic Operations (C11)

• _Atomic - Atomic type specifier

Thread Local Storage (C11)

• _Thread_local - Thread-local storage

Function Specifiers

• inline - Inline function hint (C99)
• _Noreturn - Function does not return (C11)

Notes:

1. Keywords are case-sensitive
2. Cannot be used as identifiers (variable names, function names, etc.)
3. Some keywords were introduced in later C standards (C99, C11)
4. Different compilers might support additional keywords

Best Practices:

1. Always use keywords according to their intended purpose
2. Be aware of which C standard your compiler supports
3. Some keywords might behave differently across different platforms
4. Avoid using names that are too similar to keywords for better code readability

Complete Keywords Reference Table

Keyword	Category	Description	Standard
auto	Storage Class	Automatic storage duration	C89
break	Control Flow	Exit from loop/switch	C89
case	Control Flow	Label in switch statement	C89
char	Data Type	Character data type	C89
const	Type Qualifier	Constant value	C89
continue	Control Flow	Skip to next iteration	C89
default	Control Flow	Default label in switch	C89
do	Loop	Do-while loop	C89
double	Data Type	Double-precision floating-point	C89
else	Control Flow	Alternative branch in conditional	C89
enum	Structure	Enumeration declaration	C89
extern	Storage Class	External linkage	C89
float	Data Type	Single-precision floating-point	C89
for	Loop	For loop	C89
goto	Control Flow	Jump to label	C89
if	Control Flow	Conditional statement	C89
int	Data Type	Integer data type	C89
long	Data Type	Long integer data type	C89
register	Storage Class	Register storage class	C89
return	Control Flow	Return from function	C89
short	Data Type	Short integer data type	C89
signed	Data Type	Signed modifier	C89
sizeof	Operator	Size of type/variable	C89
static	Storage Class	Static storage duration	C89
struct	Structure	Structure declaration	C89
switch	Control Flow	Multi-way decision	C89
typedef	Structure	Create type alias	C89
union	Structure	Union declaration	C89
unsigned	Data Type	Unsigned modifier	C89
void	Data Type	Empty data type	C89
volatile	Type Qualifier	Value may change unexpectedly	C89
while	Loop	While loop	C89
_Bool	Data Type	Boolean data type	C99
_Complex	Data Type	Complex number type	C99
_Imaginary	Data Type	Imaginary number type	C99
inline	Function	Inline function hint	C99
restrict	Type Qualifier	Pointer optimization hint	C99
_Alignas	Alignment	Specify alignment	C11
_Alignof	Alignment	Query alignment	C11
_Atomic	Type Qualifier	Atomic type specifier	C11
_Noreturn	Function	Function does not return	C11
_Thread_local	Storage Class	Thread-local storage	C11