For one thing, there weren't many contemporaries. Its biggest advantage was its ubiquity. It came out years before MS-DOS. Some microcomputer manufacturers had

For one thing, there weren't many contemporaries. Its biggest advantage was its ubiquity. It came out years before MS-DOS. Some microcomputer manufacturers had their own DOSs, but CP/M needed relatively little customization to run on any machine that had an 8080 or Z80-compatible processor, and in most cases it ran better and faster than the hardware manufacturer's DOS. Microsoft's first hardware product, the Z80 Softcard for the Apple II, was a bestselling product because it gave the Apple an 80 column display and CP/M 2.2 all in one package.