IBM PC-DOS (The IBM Personal Computer DOS, also known as IBM DOS) was an operating system for x86-based IBM personal computers manufactured and sold by IBM. The very first version of PC-DOS was released in August 1981 along with the IBM 5150 PC. Up to 1993, PC-DOS was developed jointly by Microsoft and IBM. However, after the split between IBM and Microsoft, they each maintained their own variant of DOS separately. IBM PC-DOS 7.0 revision 1 (marketed as PC-DOS 2000) was the last full version of DOS released by IBM, although some specialized tools make use of various builds of release 7.1 compiled between 2000 and 2003.