It's a homebrew OS.
Displays "Hello, World".
macOS
brew install nasm
brew install make
brew install qemunasm: This is Assembler. It replaces assembly code, which is a machine-understandable instruction program, with binary code, which is machine-understandable instructions, so that the computer can execute them.
make: This is a tool to automate compilation.
qemu: Pronounced "queue emu." The OS that you create yourself is run through this emulator. It is a so-called virtual machine.
By typing the make command as shown below, the qemu emulator will start and the assembly file will be compiled and executed by nasm.
make qemu