Note:

The code snippets and explanations given in this article target the Intel x86 architecture. This means you can try them on Intel 8086 to Core i7, any x86 compatible CPU from AMD or other vendor, or on an emulator like QEMU.

Also, modern technologies including GPT, EFI and GNU Multiboot have been avoided in favour of the traditional BIOS-based booting technology. It seems to be the best starting point, and is still supported by all modern machines.