Basic Data Types

The Windows API utilizes standard C/C++ data types, often with platform-specific definitions for size and signedness to ensure consistency across different architectures.

Type	Description	Common Usage
INT	Signed integer. Typically 32 bits.	Counts, sizes, general-purpose integers.
UINT	Unsigned integer. Typically 32 bits.	Flags, counts, resource identifiers.
LONG	Signed 32-bit integer.	Similar to INT, often used in older APIs.
ULONG	Unsigned 32-bit integer.	Similar to UINT.
SHORT	Signed 16-bit integer.	Smaller values, specific hardware registers.
USHORT	Unsigned 16-bit integer.	Flags, resource identifiers.
CHAR	Signed or unsigned 8-bit integer (platform-dependent).	Individual characters, small byte values.
BYTE	Unsigned 8-bit integer.	Raw byte data, buffer elements.
BOOL	Boolean value. TRUE (non-zero) or FALSE (zero).	Return values indicating success/failure, status flags.
FLOAT	Single-precision floating-point number.	Calculations requiring decimal precision.
DOUBLE	Double-precision floating-point number.	Higher precision calculations.

Pointer and Handle Types

Pointers and handles are fundamental for referencing memory and system objects.

Type	Description	Common Usage
LPVOID	Generic pointer to any type of data. Equivalent to void*.	Passing generic data buffers, memory addresses.
PVOID	Same as LPVOID.
HANDLE	A generic handle to an object managed by the operating system.	File handles, process handles, thread handles, window handles.
HMODULE	Handle to a module (DLL or executable).	Loading and managing modules.
HWND	Handle to a window.	Interacting with UI elements.

String Types

Windows supports both ANSI (ASCII) and Unicode (UTF-16) character sets. It's highly recommended to use Unicode for new development.

Type	Description	Character Set	Common Usage
LPSTR	Pointer to a null-terminated ANSI string.	ANSI	Legacy string operations.
LPCTSTR	Pointer to a null-terminated string (char* or wchar_t* depending on build settings).	TCHAR (ANSI or Unicode)	Code that can compile for either character set.
LPCWSTR	Pointer to a null-terminated Unicode (UTF-16) string.	Unicode	Modern string operations, internationalization.
LPWSTR	Pointer to a modifiable null-terminated Unicode (UTF-16) string.	Unicode	Modifying Unicode strings.

Structure and Union Types

Structures (struct) and unions (union) are used to group related data items together. Many Windows API functions operate on specific structure types.

Examples include:

• POINT: Represents a 2D point (X, Y coordinates).
• RECT: Represents a rectangle defined by two points (top-left, bottom-right).
• MSG: Contains message information for window messages.
• SYSTEMTIME: Represents date and time information.

Refer to specific API documentation for the definitions of these structures.