CP/M-86 UCSD p-System Microsoft Pascal programming language PC DOS IBM operating system BASIC operating systems MS-DOS CP/M Digital Research
Although the PC and XT included a version of the BASIC language in read-only memory, most were purchased with disk drives and run with an operating system; three operating systems were initially announced with the PC. One was CP/M-86 from Digital Research, the second was PC DOS from IBM, and the third was the UCSD p-System (from the University of California at San Diego). PC DOS was the IBM branded version of an operating system from Microsoft, previously best known for supplying BASIC language systems to computer hardware companies. When sold by Microsoft, PC DOS was called MS-DOS. The UCSD p-System OS was built around the Pascal programming language and was not marketed to the same niche as IBM's customers. Neither the p-System nor CP/M-86 was a commercial success.
