Win32Win64

Win32Win64 refers to software development and deployment that targets both 32‑bit and 64‑bit Windows platforms using the Win32 API. It describes an approach in which code is written to be portable across the two major Windows ABIs, with attention to architectural differences that arise between 32‑bit and 64‑bit environments.

Background and data models. Windows operates under different data models for 32‑bit and 64‑bit builds. In 32‑bit Windows, ILP32 applies: int, long, and pointers are 32‑bit. In 64‑bit Windows, LLP64 applies: long remains 32‑bit while long long and pointers are 64‑bit. These differences affect struct layouts, type sizes, and API interfaces that expose sizes or offsets, such as pointers, handles, and file offsets. Developers targeting both platforms must consider type widths, alignment, and portable APIs.

Compatibility and deployment. Windows provides a compatibility path for 32‑bit applications on 64‑bit systems via WOW64, which allows native 32‑bit executables to run on x64 Windows. Native 64‑bit applications run without emulation but must use 64‑bit-aware APIs and handle large address spaces. The Win32 API remains the core surface for both platforms, with attention to 64‑bit offsets, large file support, and functions that differ in signature or behavior between architectures.

Development practices. Cross‑target development commonly uses conditional compilation (for example, _WIN32 and _WIN64) and pointer‑sized types such as INT_PTR and SIZE_T. Build tools like Visual Studio and CMake support multi‑target configurations, enabling simultaneous generation of Win32 and x64 binaries. Porting typically focuses on ensuring stable data layouts, careful API use, and thorough testing on both architectures.

See also: Windows API, WOW64, PE file format, 64‑bit Windows.