How to determinate the build of app (x86 or x64) without using SDK/libs etc

Question

I want to determinate the build of the program. It can be running or not. Also I EXACLTY want to determinate such thing in my code without using any SDK or some-ready stuff from .net fw etc...

How to do it?

Question isn't about the exact language. It may references to the plain/pure C, Lisp, Basic etc...

The thing I want to know is "determination without using help-stuff like sdk etc".

PS Please! Pay attention. I've highlighted "without ready stuff like sdk", using consoles and utilities like 'dmesg', 'dumpbin' etc... Also doesn't make sense in this Q. It's more about reviewing the binary of the file by yourself without any help from another programs.

Answer 1

Linux uses "elf" executables. Checkout the elf spec for details on how to read the file directly.

Windows uses "pe" format executables. See the pe/coff spec for details.