In C, a type denotes a set of distinct interchangable values. Every object has a type, indicating the set of possible values it can hold. Every expression has a type, determined by the types of the primitive expressions it is made from, and the operators that combine them. C has several native types and several ways to construct new types.

The native types are identified by combinations of the following keywords:

type-specifier

void

char

short

int

long

float

double

signed

unsigned

_Bool

since C99

_Complex

since C99

_Imaginary

since C99

From these are built the basic types, which include the integer types and the floating-point types:

• _Bool
• char
• double
• double _Complex
• float
• float _Complex
• int
• long
• long double
• long double _Complex
• long long
• short
• signed char
• unsigned
• unsigned char
• unsigned long
• unsigned long long
• unsigned short

[: But this list includes complex types too. Do basic types include complex FP types?]

Other types can built out of structures, unions, enumerations, arrays and pointers, and alternative names for existing types can be defined with typedef.

The aggregate types are array types and structure types, i.e., those that have distinct identifiable components.

The derived types are array types, structure types, union types, pointer types and function types. All these types are defined in terms of other types, possibly recursively.

Types are identified in two ways. In a declaration, the name of an object, function or type alias is embedded in the type:

int arri[10];
int *arrpi[10];
int (*parri)[10];

arri, arrpi and parri are the names of objects being declared, and the type information surrounds them, i.e., arri is an array of 10 ints; arrpi is an array of 10 pointers to ints; parri is a pointer to an array of 10 ints. Of course, it is often simpler than that, with trivially simple embedding:

int x;

In some contexts, only the type can be identified, using the grammar of type-name:

generic-association

type-name : assignment-expression

unary-expression

sizeof ( type-name )

_Alignof ( type-name )

postfix-expression

( type-name ) { initializer-list }

since C99; Structures

( type-name ) { initializer-list , }

since C99; Structures

cast-expression

( type-name ) cast-expression

alignment-specifier

_Alignas ( type-name )

atomic-type-specifier

_Atomic ( type-name )

type-name

specifier-qualifier-list abstract-declaratoropt

specifier-qualifier-list

type-specifier specifier-qualifier-listopt

type-qualifier specifier-qualifier-listopt

type-specifier

void

char

short

int

long

float

double

signed

unsigned

_Bool

since C99

_Complex

since C99

_Imaginary

since C99

atomic-type-specifier

since C11

struct-or-union-specifier

enum-specifier

typedef-name

struct-or-union-specifier

struct-or-union identifieropt { struct-declaration-list }

struct-or-union identifier

typedef-name

identifier

struct-or-union

struct

union

struct-declaration-list

struct-declaration

struct-declaration-list struct-declaration

struct-declaration

specifier-qualifier-list struct-declarator-listopt ;

static_assert-declaration

since C11

struct-declarator-list

struct-declarator

struct-declarator-list struct-declarator

struct-declarator

declarator

declaratoropt : constant-expression

The type-name identifying arri is int[10], arrpi is int *[10], and parri is int (*)[10].