Windows Data Types

A quick reference sheet of Windows data types and their format specifiers.

For BOOL, don’t compare == TRUE, as its an int — compare != FALSE or just use the value directly since any non-zero value is truthy.

Type	Category	Underlying C type	Bits	printf (ANSI)	wprintf (Unicode)	Notes
BYTE	Unsigned int	unsigned char	8	%u or %hhu	%u or %hhu	Often used for raw byte buffers.
CHAR	Integer	char	8	%c	%c	ANSI character. Use %s for strings.
SHORT	Integer	short	16	%hd	%hd	Signed 16-bit integer.
WORD	Unsigned int	unsigned short	16	%hu	%hu	Unsigned 16-bit. Common in struct fields.
INT	Integer	int	32	%d or %i	%d or %i	Standard signed 32-bit integer.
UINT	Unsigned int	unsigned int	32	%u	%u	Unsigned 32-bit. Same width as DWORD.
LONG	Integer	long	32	%ld	%ld	Always 32-bit on Windows, unlike Linux.
ULONG	Unsigned int	unsigned long	32	%lu	%lu	Unsigned 32-bit. Very common in WinAPI.
DWORD	Unsigned int	unsigned long	32	%lu or %08lX	%lu or %08lX	Workhorse unsigned 32-bit. Hex with %lX.
DWORD32	Unsigned int	unsigned int	32	%u	%u	Explicit 32-bit, always UINT underneath.
DWORD64	Unsigned int	unsigned __int64	64	%I64u	%I64u	Use %llu on non-MSVC or with _USE_32BIT_TIME_T unset.
LONGLONG	Integer	__int64	64	%I64d	%I64d	Also valid: PRId64 with <inttypes.h>.
ULONGLONG	Unsigned int	unsigned __int64	64	%I64u	%I64u	Also valid: PRIu64. Used by FILETIME math.
INT_PTR	Pointer / handle	__int64 / int	arch	%Id	%Id	Signed, pointer-sized. 64-bit on x64, 32-bit on x86.
UINT_PTR	Pointer / handle	unsigned __int64 / unsigned int	arch	%Iu	%Iu	Unsigned pointer-sized integer.
LONG_PTR	Pointer / handle	__int64 / long	arch	%Id	%Id	Pointer-sized signed long.
ULONG_PTR	Pointer / handle	unsigned __int64 / unsigned long	arch	%Iu	%Iu	Pointer-sized unsigned long. Param for WndProc.
SIZE_T	Unsigned int	ULONG_PTR	arch	%Iu or %zu	%Iu or %zu	Result of sizeof(). %zu works in C99+ MSVC.
SSIZE_T	Integer	LONG_PTR	arch	%Id	%Id	Signed SIZE_T.
PVOID / LPVOID	Pointer / handle	void *	arch	%p	%p	Generic pointer. %p prints address.
HANDLE	Pointer / handle	void *	arch	%p	%p	Opaque handle. Print address, not value.
HWND	Pointer / handle	HANDLE	arch	%p	%p	Window handle.
HMODULE / HINSTANCE	Pointer / handle	HANDLE	arch	%p	%p	Module handle. Treat as pointer.
FARPROC	Pointer / handle	function pointer	arch	%p	%p	Cast to (void *) before printing.
CHAR / LPSTR / LPCSTR	String	char * / const char *	8	%s	%hs or %S (deprecated)	ANSI string. In wprintf, %hs is safe; %S is legacy.
WCHAR / LPWSTR / LPCWSTR	String	wchar_t * / const wchar_t *	16	%ls or %S (MSVC)	%s or %ls	Wide string. In wprintf: %s. In printf: %ls. L"..." literals.
TCHAR / LPTSTR / LPCTSTR	String	WCHAR or CHAR (UNICODE macro)	arch	%s or %ls	%s or %ls	Use _T() / TEXT() macros. Expands to WCHAR if UNICODE defined.
BSTR	String	WCHAR * (length-prefixed)	16	%ls	%s	COM string. Use SysAllocString / SysFreeString.
BOOL	Bool / status	int	32	%d	%d	TRUE=1, FALSE=0. NOT a C99 bool. Check != FALSE.
BOOLEAN	Bool / status	BYTE (unsigned char)	8	%u	%u	Used in NT native API. 0=false, non-0=true.
HRESULT	Bool / status	LONG (signed)	32	0x%08lX	0x%08lX	Always print as hex. SUCCEEDED() / FAILED() macros.
NTSTATUS	Bool / status	LONG (signed)	32	0x%08lX	0x%08lX	NT status code. NT_SUCCESS() macro.
FLOAT	Float / misc	float	32	%f or %g	%f or %g	Single-precision. Same as standard C float.
DOUBLE	Float / misc	double	64	%lf or %g	%lf or %g	Double-precision. %g trims trailing zeros.
FILETIME	Float / misc	struct { DWORD dwLowDateTime; DWORD dwHighDateTime; }	64	%I64u (combine first)	%I64u (combine first)	100ns intervals since Jan 1 1601. Cast: (ULONGLONG)ft.dwHighDateTime<<32 | ft.dwLowDateTime.
GUID / UUID	Float / misc	struct (16 bytes)	128	StringFromGUID2 or manual sprintf	StringFromGUID2 or swprintf	Print each field individually or use RPC helpers.
COLORREF	Float / misc	DWORD	32	RGB(%u,%u,%u) or 0x%06lX	0x%06lX	Packed RGB: low byte = red. Use GetRValue / GetGValue / GetBValue.