Introduction
Welcome
Welcome to Operating System development; the great frontier.
Not all "make it" in this field, many don't even pass the "Hello World" of OSDev, but perhaps you will go further and create the next Linux? Or Windows? Or are your goals lower - MenuetOS? Or even CP/M?
Whatever you goals, OSDev'ing is the great pinnacle of programming. But, you're not alone. Infact, this entire website, including the forums and this Wiki, are dedicated to OSDev'ing. This is not only about great programming skills, but is about community and developing friendships. Be those friendships between fellow forum members or IRQs and processes.
What do you need to succeed in OSDeving? You should read this article: Getting Started
Do you want to read a step-by-step tutorial to writing a basic kernel you can build upon? You should read Bran's Kernel Development Tutorial, and the article about Bran's Known Bugs.
Good luck :)
What is an Operating System?
Computer systems in general are a finite resource. Their entire purpose is to execute a set of instructions, something we commonly call a "program." This concept has not changed much over the years. Early main-frame system administrators had the job of taking program execution requests, assigning them a priority, and giving them a time frame to run. These concepts are the basis of any operating system, they just tend to occur thousands of times per second. The operating system can allow execution of multiple programs so quickly that it is virtually unnoticeable to a human user, making it seem as all the programs are running at the same time. Many things have to occur in order to allow multiple programs to execute in such a manner. The priority is safety, because if the system crashes and becomes unusable, not much else matters. Second is security, denying the capability of malicious programs, such as viruses and worms, to wreak havoc on the system is a must. Even more so is security-related software, denying access to such software's memory space is imperative. The last major issue is speed; If software runs slow or takes up valuable system resources, it makes a run-away impact on the rest of the system.
Why develop an OS?
There are quite a few reasons why someone would want to. Reason number one is "Because it's fun." Low level programming is a fun and exciting task, because you have to do everything. This may seem more difficult (it is, don't worry) but by the same reasons more fun. You know how everything works, how it all fits, and the inner-most workings of your program. An OS is no different. Having complete control over the computer is a key reason. "For school, homework, research, etc" are good enough reasons, as long as there isn't really a deadline; See Beginner Mistakes.
Making an OS is fun. It can be frustrating, and difficult, but fun.