How does wine actually work?

Question

It is clear that the environment required for running a Windows application and an Ubuntu application are completely different. But a small package (of approx. around 650 MB) is able to run Windows applications on Ubuntu. So how is this done?

It clearly won't simulate the entire Windows environment, so how far does it go by simulating the Windows environment?. What will wine do if certain setup files requite it to change registry keys (which Ubuntu does not have). Moreover, what does wine actually do while installing a Windows application on Ubuntu ?

It is not a virtual machine, so it must be missing many parts. I don't understand how far can it go, simulating the Windows environment. So briefly, what is it missing?

Answer 1

Wine (originally an acronym for "Wine Is Not an Emulator") is a compatibility layer capable of running Windows applications on several POSIX-compliant operating systems, including Ubuntu. Instead of simulating internal Windows logic like a virtual machine or emulator, Wine translates Windows API calls into POSIX calls on-the-fly, eliminating the performance and memory penalties of other methods and allowing you to cleanly integrate Windows applications into your desktop.^WineHQ

In addition to allowing the user to install and run Windows applications just like you would in Windows, Wine provides these benefits over Windows.

• Wine makes it possible to access Windows applications remotely.
• Wine makes it economical to use thin clients: simply install Wine on a Linux server, and you can access these Windows applications from any X terminal.
• Wine can also be used to make existing Windows applications available on the web by using VNC and its Java/HTML5 client.

What is missing in Wine?

Wine does not support Windows USB drivers. Windows drivers are of zero use in Wine. Wine will only present the devices that are working in the Linux system.

_{Reference: Ubuntu Community Docs: Wine}