How Does Wine Run Windows Apps on Linux? Inside the Compatibility Layer

In a casual dialogue the author highlights the chicken‑egg problem of Chinese desktop operating systems: without software they are unused, and without users developers have no incentive to create software. Although domestic distributions such as Deepin and UnionTech bundle many local applications, they cannot cover the vast Windows ecosystem, leaving users to rely on slow virtual machines like VirtualBox.

Wine offers a more efficient solution. It is not a virtual machine but a compatibility layer that forwards Windows API calls so that Windows programs can execute directly on Linux.

01 Portable CPU Instructions

Both Windows and Linux binaries are compiled for the same x86 CPU, so the actual machine instructions in the .text section are identical. The article shows a simple C function: int foo(int x) { return x * x; } When compiled on Linux the resulting ELF executable contains the same CPU instructions as the Windows PE executable, differing only in file format and metadata. This portability of the instruction stream is the foundation that Wine exploits.

02 System Calls

Operating systems expose services (file I/O, memory management, process control) through system calls. Windows and Linux implement completely different syscall interfaces, with distinct names, parameters, and semantics. An application must use these syscalls to interact with the OS.

The article illustrates this with a “Hello World” program compiled on Linux (using puts) and on Windows (using printf). Both ultimately rely on their respective C standard libraries, which in turn invoke the underlying syscalls.

To run Windows programs on Linux there are two theoretical approaches:

Re‑implement every Windows system call on Linux, essentially rewriting the OS.

Intercept Windows system calls and forward them to the equivalent Linux calls.

Wine adopts the second approach: when a Windows program issues a syscall, Wine captures it, translates it, and forwards it to the Linux kernel.

Challenges include the sheer number of undocumented Windows syscalls, many of which contain bugs or side‑effects that Wine must faithfully reproduce. Additionally, Windows graphics APIs such as DirectX have no direct Linux counterpart; the open‑source community (Valve and CodeWeavers) created Proton to translate DirectX calls to Vulkan.

03 Summary

Wine builds a bridge over the “wall of Windows” by forwarding API calls and system calls, allowing a large portion of Windows software to run on Linux despite performance and compatibility limitations. The author suggests that domestic Linux‑based operating systems can leverage Wine to enrich their software ecosystems.