Gary Kildall

CP/M and the portable operating system. Kildall wrote the PL/M language for Intel's microprocessors and then CP/M, an operating system whose hardware-specific code sat in a separate layer, the BIOS, so the same software could run on many different microcomputers. Digital Research, which he founded with his wife Dorothy McEwen, sold it widely in the late 1970s before IBM chose Microsoft's DOS for its PC. He died in 1994.