Bootloader and real mode programming demo

There is a makefile provided to automatically build binaries, and set them up on a disk image file named disk.hdd. To construct all of this, open up your terminal, cd to the root directory of this repository and run the command "make".

The disk image file can then be used with virtual machine software such as VirtualBox.

Note that this project is not an operating system.

The source code is split over three directories, for three quite different tasks.

Code for the bootsector is contained in bootsector/, which is written entirely in assembly, compatible with the GNU assembler. This is kept very simple; no filesystem is used, the bootsector loads a number of sectors starting immediately after the bootsector on the disk into memory, then starts executing them. The number of sectors to be loaded is implanted into the bootsector at install time by a special purpose program contained in the tools/ directory.

The program that the bootsector loads is contained in the memtest/ directory, and is compiled into a flat binary format, the same as for the bootsector. This format means that the bootsector does not need to understand anything about executable file formats, keeping things simple.

The memtest program will make use of BIOS calls to obtain information about what memory is available on the computer, then print the information on the screen, also with BIOS calls.