A bare-bones kernel that prints "Hello, World!" on the screen.

1. QEMU:
QEMU is a machine emulator and virtualizer.
Install it using:
1. Linux: $ sudo apt-get install qemu-system
2. Mac OS: brew install qemu

2. NASM:
NASM is an assembler and disassembler for the Intel x86 architecture.
Install it using: $ sudo apt-get install nasm

1. Build kernel executable: ./buildkernel.sh
2. Place the kernel executable in the grub image: ./buildimage.sh
3. Run the kernel: ./run.sh

1. Use NASM to produce an object file of entry.asm.
   * nasm -f elf32 entry.asm -o entry.o
   * elf32 flag is used to produce a 32-bit ELF object file.

2. Use cc to produce an object file of c_start.c. * cc -m32 -c -Wall c_start.c
   * From the man page of gcc:
   -m32
Generate code for a 32-bit or 64-bit environment.
The -m32 option sets "int", "long", and pointer
types to 32 bits, and generates code that runs on
any i386 system.

3. Use ld (the GNU Linker) to link the above object files into a single executable (hydrogen). * ld -m elf_i386 -T link.ld -o hydrogen c_start.o entry.o * elf_i386 flag is used to emulate the elf_i386 linker. * link.ld is a linker template file.

sudo losetup /dev/loop0 references/grub.img  

sudo mkdir /mnt/sos

sudo mount /dev/loop0 /mnt/sos

sudo cp hydrogen /mnt/sos/SOS

sudo sync

sudo umount /dev/loop0

sudo losetup -d /dev/loop0

• -fda option tells qemu to use grub.img as a floppy disk image.