Grubless is an attempt at recreating a basic, 32-bit general purpose OS from scratch using nothing more than x86 assembly(nasm) and C.
sudo apt-get install nasmsudo apt-get install qemu-system-x86sudo apt install mtoolssudo apt install dosfstoolsClone the repository onto your local machine using git:
git clone https://github.com/Serpent03/grubless.gitTo run the operating system, use make all to build the operating system image. If you do not want to build again, then use make run to run the already built binary.
There are two "phases" of the operating system booting up: the initial boot, and then loading the kernel. Accordingly, the files for operations in both the bootup and kernel phases can be found inside source/boot and source/kernel respectively.
The reason that boot and kernel are different phases has to do with the fact that during bootup, an instruction size of only 16-bit is available to us.
All function addresses, BIOS routines, and operands are constrained to this size. This effectively means that we are constrained to about 2^16(or 65536), or more commonly: 64KB of RAM.
That's not a lot - especially for writing an OS. To make up for this deficiency, we have to switch to a 32-bit instruction size, which allows us 2^32 various different memory locations: a whopping 4GB of RAM(doesn't seem like much nowadays does it?)
Unfortunately, this switch to 32-bit means that functions, routines, etc. of 16-bit instruction size are all inaccessible, so we have to write a lot of stuff from scratch - all of which goes inside the src/kernel folder.
For more details, check out the wiki!