This section summarizes the syntax of the C language, using the syntax of the ANSI C Standard. Syntactic categories are indicated with bold type, and literal words or characters are indicated with monospaced, nonitalicized type. A colon following a syntactic category introduces its definition. Alternative definitions are listed on separate lines, or are prefaced by the words "one of." An optional element is indicated by the subscript _opt. For example, the following line indicates an optional expression enclosed in braces:

{ expressionopt }

The section numbers shown in parentheses refer to the section of the American National Standard for Information Systems-Programming Language C (document number: X3.159-1989) that discusses that part of the language.

A.1.1 Lexical Grammar

A.1.1.1 Tokens

token: (§3.1)

keyword identifier constant string-literal operator punctuator

preprocessing-token: (§3.1)

header-name identifier pp-number character-constant string-literal operator punctuator each nonwhite-space character that cannot be one of the above

A.1.1.2 Keywords

keyword: (§3.1.1) one of

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 _Bool _Complex (ALPHA ONLY)

A.1.1.3 Identifiers

identifier: (§3.1.2)

identifier-nondigit identifier identifier-nondigit identifier digit

identifier-nondigit:

nondigit other implementation-defined characters

nondigit: §3.1.2 one of

a b c d e f g h i j k l m n o p q r s t u v w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z _

digit: (§3.1.2) one of

0 1 2 3 4 5 6 7 8 9

A.1.1.4 Constants

constant: (§3.1.3)

floating-constant integer-constant enumeration-constant character-constant

floating-constant: (§3.1.3.1)

decimal-floating-constant hexadecimal-floating-constant

decimal-floating-constant

fractional-constant exponent-partopt floating-suffixopt digit-sequence exponent-part floating-suffixopt

hexadecimal-floating-constant

hexadecimal-prefix hexadecimal-fractional-constant binary-exponent-part floating-suffixopt hexadecimal-prefix hexadecimal-digit-sequence binary-exponent-part floating-suffixopt

fractional-constant: (§3.1.3.1)

digit-sequenceopt . digit-sequence digit-sequence .

exponent-part: (§3.1.3.1)

e signopt digit-sequence E signopt digit-sequence

sign: (§3.1.3.1) one of

+ -

digit-sequence: (§3.1.3.1)

digit digit-sequence digit

hexadecimal-fractional-constant:

hexadecimal-digit-sequenceopt . hexadecimal-digit-sequence hexadecimal-digit-sequence .

binary-exponent-part:

p signopt digit-sequence P signopt digit-sequence

hexadecimal-digit-sequence:

hexadecimal-digit hexadecimal-digit-sequence hexadecimal-digit

floating-suffix: (§3.1.3.1) one of

f l F L

integer-constant: (§3.1.3.2)

decimal-constant integer-suffixopt octal-constant integer-suffixopt hexadecimal-constant integer-suffixopt

decimal-constant: (§3.1.3.2)

nonzero-digit decimal-constant digit

octal-constant: (§3.1.3.2)

0 octal-constant octal-digit

hexadecimal-constant: (§3.1.3.2)

0x hexadecimal-digit 0X hexadecimal-digit hexadecimal-constant hexadecimal-digit

nonzero-digit: (§3.1.3.2) one of

1 2 3 4 5 6 7 8 9

octal-digit: (§3.1.3.2) one of

0 1 2 3 4 5 6 7

hexadecimal-digit: (§3.1.3.2) one of

0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F

integer-suffix: (§3.1.3.2)

unsigned-suffix long-suffixopt long-suffix unsigned-suffixopt

unsigned-suffix: (§3.1.3.2) one of

u U

long-suffix: (§3.1.3.2) one of

l L

enumeration-constant: (§3.1.3.3)

identifier

character-constant: (§3.1.3.4)

' c-char-sequence' L' c-char-sequence'

c-char-sequence: (§3.1.3.4)

c-char c-char-sequence c-char

c-char: (§3.1.3.4)

any member of the source character set except the single-quote ('), backslash (\), or new-line character escape-sequence

escape-sequence: (§3.1.3.4)

simple-escape-sequence octal-escape-sequence hexadecimal-escape-sequence

simple-escape-sequence: (§3.1.3.4) one of

\' \" \? \\ \a \b \f \n \r \t \v

octal-escape-sequence: (§3.1.3.4)

\ octal-digit \ octal-digit octal-digit \ octal-digit octal-digit octal-digit

hexadecimal-escape-sequence:(§3.1.3.4)

\x hexadecimal-digit hexadecimal-escape-sequence hexadecimal-digit

A.1.1.5 String Literals

string-literal: (§3.1.4)

"s-char-sequenceopt" L"s-char-sequenceopt"

s-char-sequence: (§3.1.4)

s-char s-char-sequence s-char

s-char: (§3.1.4)

any member of the source character set except the double-quote ("), backslash (\), or new-line character escape-sequence

A.1.1.6 Operators

operator: (§3.1.5) one of

[ ] ( ) . -> ++ -- & * + - ~ ! sizeof / % << >> < > <= >= == != ^ | && || ? : = *= /= %= += -= <<= >>= &= ^= |= , # ##

A.1.1.7 Punctuators

punctuator: (§3.1.6) one of

[ ] ( ) { } * , : = ; ... #

A.1.1.8 Header Names

header-name: (§3.1.7)

<h-char-sequence> "q-char-sequence"

h-char-sequence: (§3.1.7)

h-char h-char-sequence h-char

h-char: (§3.1.7)

any member of the source character set except the new-line character and >

q-char-sequence: (§3.1.7)

q-char q-char-sequence q-char

q-char: (§3.1.7)

any member of the source character set except the new-line character and "

A.1.1.9 Preprocessing Numbers

pp-number: (§3.1.8)

digit . digit pp-number digit pp-number nondigit pp-number e sign pp-number E sign pp-number .

A.1.2 Phrase Structure Grammar

A.1.2.1 Expressions

primary-expression: (§3.3.1)

identifier constant string-literal ( expression )

postfix-expression: (§3.3.2)

primary-expression postfix-expression [ expression ] postfix-expression ( argument-expression-listopt ) postfix-expression . identifier postfix-expression -> identifier postfix-expression ++ postfix-expression - -

argument-expression-list: (§3.3.2)

assignment-expression argument-expression-list , assignment-expression

unary-expression: (§3.3.3)

postfix-expression ++ unary-expression - - unary-expression unary-operator cast-expression sizeof unary-expression sizeof ( type-name )

unary-operator: (§3.3.3) one of

& * + - ~ !

cast-expression: (§3.3.4)

unary-expression ( type-name ) cast-expression

multiplicative-expression: (§3.3.5)

cast-expression multiplicative-expression * cast-expression multiplicative-expression / cast-expression multiplicative-expression % cast-expression

additive-expression: (§3.3.6)

multiplicative-expression additive-expression + multiplicative-expression additive-expression - multiplicative-expression

shift-expression: (§3.3.7)

additive-expression shift-expression << additive-expression shift-expression >> additive-expression

relational-expression: (§3.3.8)

shift-expression relational-expression < shift-expression relational-expression > shift-expression relational-expression <= shift-expression relational-expression >= shift-expression

equality-expression: (§3.3.9)

relational-expression equality-expression == relational-expression equality-expression != relational-expression

AND-expression: (§3.3.10)

equality-expression AND-expression & equality-expression

exclusive-OR-expression: (§3.3.11)

AND-expression exclusive-OR-expression ^ AND-expression

inclusive-OR-expression: (§3.3.12)

exclusive-OR-expression inclusive-OR-expression | exclusive-OR-expression

logical-AND-expression: (§3.3.13)

inclusive-OR-expression logical-AND-expression && inclusive-OR-expression

logical-OR-expression: (§3.3.14)

logical-AND-expression logical-OR-expression || logical-AND-expression

conditional-expression: (§3.3.15)

logical-OR-expression logical-OR-expression ? expression : conditional-expression

assignment-expression: (§3.3.16)

conditional-expression unary-expression assignment-operator assignment-expression

assignment-operator: (§3.3.16) one of

= *= /= %= += -= <<= >>= &= ^= |=

expression: (§3.3.17)

assignment-expression expression , assignment-expression

constant-expression: (§3.4)

conditional-expression

A.1.2.2 Declarations

declaration: (§3.5)

declaration-specifiers init-declarator-listopt ;

declaration-specifiers: (§3.5)

storage-class-specifier declaration-specifiersopt type-specifier declaration-specifiersopt type-qualifier declaration-specifiersopt

init-declarator-list: (§3.5)

init-declarator init-declarator-list , init-declarator

init-declarator: (§3.5)

declarator declarator = initializer

storage-class-specifier: (§3.5.1)

typedef extern static auto register

type-specifier: (§3.5.2)

void char short int long float double signed unsigned _Bool _Complex (ALPHA ONLY)

struct-or-union-specifier enum-specifier typedef-name

struct-or-union-specifier: (§3.5.2.1)

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

struct-or-union: (§3.5.2.1)

struct union

struct-declaration-list: (§3.5.2.1)

struct-declaration struct-declaration-list struct-declaration

struct-declaration: (§3.5.2.1)

specifier-qualifier-list struct-declarator-list ;