C++ Keywords

Article
09/28/2012

Keywords are predefined reserved identifiers that have special meanings. They cannot be used as identifiers in your program. The following keywords are reserved for Microsoft C++. Names with leading underscores are Microsoft extensions.

__abstract 2	__alignof Operator	__asm
__assume	__based	__box 2
__cdecl	__declspec	__delegate2
__event	__except	__fastcall
__finally	__forceinline	__gc 2
__hook 3	__identifier	__if_exists
__if_not_exists	__inline	__int16
__int32	__int64	__int8
__interface	__leave	__m128
__m128d	__m128i	__m64
__multiple_inheritance	__nogc 2	__noop
__pin 2	__property 2	__raise
__sealed 2	__single_inheritance	__stdcall
__super	__thiscall	__try/__except, __try/__finally
__try_cast 2	__unaligned	__unhook 3
__uuidof	__value 2	__virtual_inheritance
__w64	__wchar_t, wchar_t	abstract
array	auto	bool
break	case	catch
char	class	const
const_cast	continue	decltype
default	delegate	delete
deprecated1	dllexport1	dllimport1
do	double	dynamic_cast
else	enum	enum class
enum struct	event	explicit
extern	false	finally
float	for	for each, in
friend	friend_as	gcnew
generic	goto	if
initonly	inline	int
interface class	interface struct	interior_ptr
literal	long	mutable
naked1	namespace	new
new	noinline1	noreturn1
nothrow1	novtable1	nullptr
operator	private	property
property1	protected	public
ref class	ref struct	register
reinterpret_cast	return	safecast
sealed	selectany1	short
signed	sizeof	static
static_assert	static_cast	struct
switch	template	this
thread1	throw	true
try	typedef	typeid
typeid	typename	union
unsigned	using declaration, using directive	uuid1
value class	value struct	virtual
void	volatile	while

1 Extended attributes for the __declspec keyword.

2 Applicable to Managed Extensions for C++ only. This syntax is now deprecated.

3 Intrinsic function used in event handling.

See Component Extensions for Runtime Platforms for more information.

Microsoft Specific

In Microsoft C++, identifiers with two leading underscores are reserved for compiler implementations. Therefore, the Microsoft convention is to precede Microsoft-specific keywords with double underscores. These words cannot be used as identifier names.

Microsoft extensions are enabled by default. To ensure that your programs are fully portable, you can disable Microsoft extensions by specifying the ANSI-compatible /Za command-line option (compile for ANSI compatibility) during compilation. When you do this, Microsoft-specific keywords are disabled.

When Microsoft extensions are enabled, you can use the Microsoft-specific keywords in your programs. For ANSI compliance, these keywords are prefaced by a double underscore. For backward compatibility, single-underscore versions of all the double-underscored keywords except __except, __finally, __leave, and __try are supported. In addition, __cdecl is available with no leading underscore.

The __asm keyword replaces C++ asm syntax. asm is reserved for compatibility with other C++ implementations, but not implemented. Use __asm.

The __based keyword has limited uses for 32-bit and 64-bit target compilations.

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C++ Keywords

Microsoft Specific

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