What is a disk operating system?

Answer 1

Answer

An operating system (OS) is software that controls the internals of a computer. The first large computers did not have operating systems or programming languages. You entered insructions through lights on the main console. The first operating systems were on punched cards, which you read into computer memory. They would then control instructions entered on decks of punched cards (a "computer program"). When you turned off the computer, the memory would NOT be cleared, so the next time you turned on the computer, the operating system would still be there. At this time, computers consisted of a "central processor" (the equivalent of a mother board today) that took up a room, punched cards input and output, and printers. There were no magnetic devices such as tapes or hard or floppy disk. The problem with this was that it required that everything from your operating system to your program be entered in "machine" language - binary codes that told the processor what to do (move something, compare something, add, subtract etc.). The next step was to create an operating system that was "flexible" and easily updated. So the "TOS", or Tape Operating System was created. This consisted of adding a tape drive to the computer complex, and storing the "OS" card deck on tape. About this time, they changed over to "volatile" memory that was cleared when you powered down the computer, so the OS had to be re-loaded every time when you turned it back on.

In this way, if you wanted to change operating systems (go from a financial operating system that handled money to a scientific OS that handled spiral decay of satellites), you just stored that OS on a tape and mounted the tape you wanted, which you then loaded into memory. It was at this point that the "general purpose" computer was born. Up until then, each computer was dedicated to a task such as financial, or scientific or military.

The computer then evolved into "magnetic" systems - tape, disk, cylinders, platters, CRAM (Card Random Access Memory) - there were many different kinds of storage that could be used for input and output. The next logical step was to take the TOS and put it out on disk (or even magnetic cards), so you didn't have to mount a tape to load or change an operating system. This was DOS (Disk Operating System). DOS was originally on mainframe computers.

At the same time mainframe computers were maturing, so was the "hobby" computer. It followed the same path as mainfame, only slower, so it went through a "console lights" phase where you could only do something through the lights and/or switches, into an "operating system" on tape and finally into a DOS (of which there were several flavors). Today, most operating systems are DOS, but they might be stored on media other than disk, such as Thumb Drives, which are really solid state chips and not disk drives. The PC "BIOS", the Basic Input/Output Operating System, is an example of a DOS on a chip that is used to initialize your computer so it can read/write from all the devices that it consists of.