I started my 64-bit experience by installing the 64-bit Windows Vista Ultimate OS. Let me tell you, the installation process, look and feel and everything of the OS is just like its 32-bit variant. No difference at all! So, don't expect to look at the desktop and figure out if it's a 64-bit or a 32-bit! The only way to figure that out is to check your system properties, which gives you the following screen... See at the bottom where it mentions, that this is a 64-bit Operating System
Fine, so I was done, installing the OS now; what was new? The very first question I had was, Do I strictly need 64-bit applications for installing & running them on a 64-bit OS? The answer is 'NO'! You can very much run your 32-bit apps. However, the device drivers need to be 64-bit compulsorily. All hardware devices need 64-bit drivers to work on a 64-bit version of Windows. So if you are running some old legacy devices (quite unlikely) first make sure that 64-bit OS specific drivers for the same are available! I got a nice error screen while I tried to install 32-bit display drivers for my GeForce 7600GS Video Card.
So, how does Windows allow you to install 32-bit apps on a 64-bit OS? The answer to this is WOW64! Now I know, Vista was majorly using this keyword 'WOW' in the Vista marketing campaigns and product promotions, but there is a lot of difference in both these WOW's :-D! The WOW that I am talking about stands for 'Windows 32-bit on Windows 64-bit (WOW64 or WOW)', a subsystem of the OS.
What's the big deal? I mean, I have a 64-bit OS, I'll install an application & expect it to run. What's with these numbers? What's with the difference in 64-bit & 32-bit? The issues are related to the 64-bit processors and Windows itself.
The processors run in two modes: 32-bit and 64-bit. In the 64-bit mode, the memory pointers are larger than in the 32-bit mode. While this gives the 64-bit applications access to more memory, the execution contexts and data are incompatible with 32-bit applications. As a result, 64-bit and 32-bit code cannot be mixed within a single process. For example, if a 64-bit process loads a 32-bit Dynamic Link Library (DLL), or vice versa, an error results, saying that the DLL format is incorrect. Consequently, 32-bit applications cannot use the 64-bit system DLLs. WOW64 solves these and other problems.
That's all that I know about WOW... and also one more thing... Wondered how the segregation of 32-bit and 64-bit applications is done by Windows OS while installing a new program/ application? Well Well Well, Vista makes a new folder, 'Program Files (x86)' & also just 'Program Files'. As the name suggests, 1 is for storing your 32-bit apps while the other one is for you 64-bit apps!
That's all I know about the 64-bit OS. If you have any questions or even extra information to share, please drop in a comment. I'll try to answer the questions, if I can & would be more than happy to learn more, from the extra info that you might have for me :-)
