What's Left

What you do next to your kernel is completely up to you. The next thing you should think of writing is a memory manager. A memory manager will allow you to grab chunks of memory so that you can dynamically allocate and free memory as you need it. Using a memory manager, you can use more complicated data structures such as linked lists and binary trees to allow for more efficient storage and manipulation of data. It's also a way of preventing applications from writing to kernel pages, which is a feature of protection.

It's possible to write a VGA driver, also. Using a VGA driver, you can set up different graphics modes in your kernel, allowing higher resolutions and graphical display options such as buttons and images. If you want to go further, you could eventually look into VESA video modes for high color and higher resolutions.

You could eventually write a device interface which would allow you to load or unload kernel 'modules' as you need them. Add support for filesystems and disk drives so that you can access files off disks and open applications.

It's very possible that you add multitasking support and design scheduling algorithms to give certain tasks higher priority and longer time to run according to what the application is designed to run at. The multitasking system closely relies on your memory manager to give each task a separate space in memory.

Example kernel online source tree

start.asm
gdt.c
idt.c
irq.c
isrs.c
kb.c
main.c
scrn.c
timer.c
include/system.h
link.ld
build.bat
dev_kernel_grub.img

Get the whole tutorial and example kernel here (110KBytes).

I hope that this tutorial has given you a more thorough understanding of some of the various low-level items involved in creating a kernel: a driver for your processor and memory.