What language did Bill Gates and Paul Allen create?

In 1981, Bill Gates and Paul Allen purchased the rights to a basic computing language called QDOS (Quick and Dirty Operating System), and built it up into the first version of MS-DOS(Microsoft Disk Operating System).

MS-DOS shipped with the very first IBM PCs, back in the early 1980s; by 1985, Gates and Allen were ready to introduce the first Microsoft GUI (graphical user interface), Windows 1.0, which also used MS-DOS as its underlying operating system.