MS DOS
DOS or Disk Operating System was one of the first operating systems written for the IBM compatible personal computers.
Although others existed, DOS was the first one that became heavily available to the general public.
Originally created by International Business Machines (IBM), it was purchased by our good friend Bill Gates of Microsoft for a few thousand dollars.
Unlike the operating systems of today (i.e. Windows XP) with their easy to use, user-friendly feel, DOS is rather primitive.
In order to use Microsoft DOS, you first had to master a series of keyboard commands, simply meaning, you had to type what you wanted it to do. However, once you learned these commands it was relatively easy to use.
Learn More About DOS and Windows Operating Systems