MS-DOS

MS-DOS was the operating system of the personal-computer boom. Microsoft licensed it to IBM for the 1981 PC after buying a clone called 86-DOS for a few tens of thousands of dollars, then sold it to every PC maker that followed. For most of the 1980s the world’s office and home computers booted to its terse command prompt, where users typed file paths and ran programs by name. Graphical Windows first sat on top of it, but the NT line eventually made it unnecessary. The last standalone version shipped hidden beneath Windows Me in 2000; Windows XP severed the link in 2001.