How do I check OS with a preprocessor directive?

How do I check OS with a preprocessor directive?

c operating-system c-preprocessor conditional-compilation

c

Programmatically get the cache line size?

c++ c caching operating-system systems-programming

c

How are everyday machines programmed? [closed]

c operating-system microcontroller embedded assembly

c

Spinlock versus Semaphore

c++ c linux unix operating-system

c

How can I build a small operating system on an old desktop computer? [closed]

c operating-system bootstrapping osdev assembly

c

dup2 / dup - why would I need to duplicate a file descriptor?

c linux operating-system system-calls

c

Is memory allocation a system call?

c++ c operating-system heap

c

Maximum memory which malloc can allocate

c memory-management operating-system malloc cpu-architecture

c

In C, how is the main() method initially called?

c operating-system

c

Is it true that fork() calls clone() internally?

c linux operating-system system-calls

c

Who decides the sizeof any datatype or structure (depending on 32 bit or 64 bit)?

c++ c linux compiler-construction operating-system

c

stdout thread-safe in C on Linux?

c linux unix operating-system

c

Why are malloc() and printf() said as non-reentrant?

c unix operating-system reentrancy

c

What happens in OS when we dereference a NULL pointer in C?

c pointers null operating-system

c

Are there any macros to determine if my code is being compiled to Windows? [duplicate]

c++ c operating-system c-preprocessor

c