A simple operating system for x86-64 UEFI machines written in C and assembly. Made as an experiment to see if I could actually develop something so low-level as an OS.

For now, DexprOS is able to:

• setup graphics using UEFI Graphics Output Protocol,
• exit UEFI boot services,
• set up its own 4-level or 5-level page map,
• load a working General Descriptor Table and Interrupt Descriptor Table,
• setup PIC (Programmable Interrupt Controller) and PS/2 controller,
• handle keyboard input and convert it to unicode characters,
• process a few commands in a simple shell: echo, clear, help, shutdown, reboot.

As DexprOS is just an experiment and my focus goes mainly to other projects, new features may be introduced slowly over time.
Here are my upcoming plans:

• memory allocation,
• syscalls,
• userspace code execution,
• parsing some ACPI structures.

The supported compilers are:

• Clang. When compiling with Clang, a toolchain file isn't required. A proper target is set automatically when configuring the project.
• MinGW cross-compiler. Within the cmake/cross-compile-toolchains directory, there is a CMake Toolchain file to easily cross-compile the code on Linux if you have MinGW installed.

You can use CMake directly or execute either build-clang.bash or build-mingw.bash script if you're running Linux.

To run on real hardware, create a bootable FAT32 partition on a USB drive. Then copy the BOOTX64.EFI file from your build directory to /EFI/BOOT/BOOTX64.EFI on your USB.

You can also use the generate-img.bash script to generate a disk image that you can run under QEMU.

• GNU EFI (bundled with the project itself in third-party/gnu-efi-code),

• Either Clang or MinGW cross-compiler,
• CMake build system.