“Win32” is the term used when discussing Windows 32 bit operating systems or technology. In the context of programming, it usually refers to the API for programming directly to the Windows low level functions and data structures.
Before Win32 was Win16. Windows 3.11 (the version before Windows 95) was the last version of Windows before Microsoft added 32bit capability to all of their desktop and server operating system. The function calls and data structures in 16 bit were very similar to the ones in 32 bit Windows. As a matter of fact, most of the Win16 APIs are still available in the latest versions of Windows, but only for backward compatibility. No one writes software these days that depends on the 16 bit APIs in Windows. 32 bit Windows has been around since the early 1990’s, starting with Windows NT around 1993.
For nearly 10 years, 64bit versions of Windows have been around, though few people have been using them. When Microsoft first made 64bit versions of Windows available, only the most expensive, top of the line CPU chips were capable of running them, therefore, few developers wrote code specifically for 64 bit.
Today, “Win32” is just the generic term for Windows APIs, even when discussing 64 bit programming.
These days, it’s hard to find a CPU chip that’s not fully 64 bit, but most people still choose to install the 32bit version of Windows XP, Vista, or Windows 7. But, since Vista was released, more and more people are switching to 64 bit versions of Windows. They’d been avoiding it because there were compatibility problems with older software that wasn’t written right and as a result, failed under 64 bit windows. Most modern software runs just fine under 64 bit Windows now.
Since the release of Windows 7, Microsoft has tightened up the Windows Logo requirements so that any software requesting the Windows Logo rights must pass a rigorous 64 bit test. Microsoft is heavily pushing 64 bit Windows. It’s about time too, because 32 bit Windows is incapable of using more than 4GB of RAM. Up to a couple of years ago, that wasn’t an issue because until then, it wasn’t even possible to have that much memory. But, with the continually rapid pace of technological advancement, anyone can get memory for less than $30 per GB. Computers with more than 4GB are not only possible today, but common place. To use the rest of your memory, you MUST have a 64bit operating system.