Keywords (C++)


The latest version of this topic can be found at Keywords (C++).

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 __delegate 2
__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
deprecated 1 dllexport 1 dllimport 1
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
naked 1 namespace new
new noinline 1 noreturn 1
nothrow 1 novtable 1 nullptr
operator private property
property 1 protected public
ref class ref struct register
reinterpret_cast return safecast
sealed selectany 1 short
signed sizeof static
static_assert static_cast struct
switch template this
thread 1 throw true
try typedef typeid
typeid typename union
unsigned using declaration, using directive uuid 1
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.

END Microsoft Specific

See Also

Lexical Conventions
C++ Operators