Windows API Reference – Terminology

A generic pointer to an opaque object used by the Windows operating system to reference resources such as files, windows, or processes.

Long pointer to a value passed as a message parameter. In 64‑bit builds it is a 64‑bit integer.

The result of a window procedure call; typically a signed integer used to convey status or data back to the system.

Double word – a 32‑bit unsigned integer. Frequently used for flags, sizes, and identifiers.

A 32‑bit value used to indicate success or failure of COM and Win32 functions. The highest bit denotes failure (1) or success (0).

A service control manager handle used with the Service Control API to manage Windows services.

Process Environment Block – a data structure in user mode that contains information about a process.

Portable Executable – the file format for executables, DLLs, and other binary modules in Windows.

Class Identifier – a GUID that uniquely identifies a COM class object.

Windows API Reference – Terms