What software is required to have a functional computer?

I'm trying to build my own computer, but I don't know what software is Absolutely Needed for my computer to be functional. I Know an OS but what other ones are there?What software is required to have a functional computer?
OS

%26lt;Windows XP/2000%26gt;

%26lt;Windows Vista%26gt;

%26lt;Windows 7%26gt;

%26lt;Macintosh%26gt;

%26lt;Linux%26gt;



Firefox should be required, since it's really the only safe browser.



Security is a major thing with computers. ZoneAlarm Firewall, Synmatic Antivirus, Spybot Search%26amp;Destroy.What software is required to have a functional computer?
First to correct your terminology... you are NOT going to BUILD a computer unless you make the transistors yourself. What you are going to do is ASSEMBLE a computer by collecting parts and software other people have made. You need SYSTEMS of components. First and foremost the Central Processing Unit (CPU). To that you add memory. And finally, you load a program into memory and push the button that says RUN the program. The simplest logic circuit is the AND gate. It has two inputs. The output goes high if and only if the inputs are BOTH high. An OR gate is equally simple. The output goes high if and only if ONE input is high. These circuits and many more are all assembled in the CPU which is what makes it work to process instructions. So, buy a case and power supply. Buy a motherboard. Buy memory and CPU that fits the motherboard. Buy disk drives. Buy an Operating System that will run on the system you assemble. Research. Do the homework. Find out what is out there and available and will work together. What you ask here is too complex for me to name names. There are simply too many makes and models, literally. I have an early computer I built from a kit in 1976. It cost me $200, half of it was for the CPU chip alone. It has a CPU, 256 bytes of memory and toggle switches for input and 7 segment hexadecimal LED display digits for output. It has 16 bytes of read only memory which contains a MONITOR program which lets the CPU know how to accept input from the switches, display an output and store a program in memory. That 16 bytes of ROM programming (software) is the minimum which makes this computer "functional" as you put it. A slide rule (do you even KNOW what THAT is?) is a fully functional analog computer for multiplication and division. Do you understand now why it is your question makes little sense and actually has no definitive answer? Buy a book, take a class or visit your local library. Maybe there is a "Computers for Dummies" book out there that will teach you enough to know what you really want to know the answer to...What software is required to have a functional computer?
You need a boot loader, and a kernel along with it's dependencies, and a software package manager that supports CLI. That's the bare minimum needed to have a functional computer in terms of software.



As to what's necessary for ease of use you need a GUI environment like Gnome, Fluxbox, Xfce, KDE, Windows (it's more than just an OS), ICEwm etc., which of course means you'll need (if it's not Windows) X window manager and it's dependencies.
there is planty of OS that are functional for computers like windows xp - 7 or linux kernel leopard

but i don't think that there is something else than the OS for a computer