Gary Kildall was a pioneer of personal computer software. He wrote programming language tools, including assemblers (Intel 4004), interpreters (BASIC), and compilers (PL/M). He created a widely-used disk operating system (CP/M). He and his wife, Dorothy McEwen, started a successful company called Digital Research to develop and market CP/M, which for years was the dominant operating system for personal microcomputers. Thousands of programs were written to run under it, and a million or more people might have used it.