I was inspecting the preprocessed output of my C program and happened to look at the header file wordsize.h

It is located in /usr/include/i386-linux-gnu/bits/wordsize.h

the file contains only one macro

#define __WORDSIZE   32

My question is, is the wordsize then being decided by the compiler that is installed or does it has something to do with the OS that I have installed (32 bit or 64 bit) or does it have something to do with the Hardware configuration of my machine.

I am new to development under Linux.