An API developed by Microsoft in 1992 for their Windows operating system. A decent (but not excellent) API to code in, it handles stuff like creating windows, drawing polygons, application-to-application interface, and anything else required to make an operating system *cough* perform.

Win32 allows programmers to code Windows applications in a flexible environment.

Win32 supports the following:

32-bit applications
A 32-bit processor works faster with a 32-bit data word/operand. A 32-bit number can represent 4,294,967,295 values, where a 16-bit number is limited to 65,535. In order to take advantage of 32-bit capabilities, a program must be written for a 32-bit environment.

Multithreading
Win32 allows applications to have more than one thread (or task) executed. Multithreading allows an application to be more responsive to the user. Multithreading takes advantage of multiprocessing automatically. Threads are scheduled preemptively.

Large address spaces
Win32 allows up to 2 Gigabytes of contiguous unsegmented address space. This allows programs to grow without using complex mechanisms like segmenting and overlays. Larger address space allows programs to work with larger data sets.

Memory protection between applications
Each application is protected from other applications because each app has its own data space. Also, an app cannot make unauthorized modifications to other executables ot the OS. This helps make Windows NT a safer OS than Win9x, for example.

Advanced application services
Examples are OpenGL, DirectX, ActiveX, OLE and individual input queues.