MS-DOS was created by a company called Seattle Computer Systems and later purchased by Microsoft. It was patterned after CP/M to provide compatibility with the existing installed base of business applications such as WordStar and dBase.
MS-DOS grew to include more features from other operating systems. MS-DOS 2.0 introduced features from Unix such as subdirectories, command input/output redirection, and pipes.
MS-DOS was not designed to be a multi-user or multitasking operating system, but many attempts were made to retrofit these capabilities. Many programs were developed using the terminate and stay resident (TSR) function and other mostly-undocumented functions to provide pop-up applications. Add-on environments like DesqView attempted to provide multitasking, and achieved a fair degree of success when later combined with the memory-management hardware of the Intel 80386 CPU processor.
After the release of the Apple Macintosh in 1984, people became interested in a graphical user interface. Many programs created their own graphical interface, such as Microsoft Word for DOS and the Norton Shell. However, that required duplication of effort and did not provide much consistency, so complete GUI environments were created. Digital Research created the GEM environment with minimal popularity, but it was soon eclipsed by Microsoft's own Windows.