Readers Respond: 25 More Top Technologies

The article “25 More Top Technologies” refers to CP/M and QDOS as “the spiritual and the actual parents, respectively, of what became MS-DOS” [Sept. 18].

Its sad to see CP/M, the operating system that helped establish the largest part of the PC market before the IBM PC, given the same status as QDOS, a functional equivalent of CP/M that existed only long enough to be bought by a young Microsoft. For decades since, there have been arguments and court cases over the relationship between CP/M and QDOS.

Your one-line gloss does yet another injustice to history and Gary Kildall [the founder of Digital Research]. CP/M was the first product of Digital Research and was developed by Kildall as early as 1973. It became a product when offered as part of IMSAIs earliest floppy disk systems. CP/M-80 and, later, CP/M-86 were sold in enormous quantities through the early 1980s, and CP/M was the standard operating system for Intel- and Zilog-based computers.

Even after the IBM PC standardized on MS-DOS in 1981, Digital Research sold CP/M and other multitasking and multiuser products for many years (before Digital Research itself was sold).

QDOS, on the other hand, was written by a single programmer who readily admits to having had a CP/M manual in hand. He was obliged to do so because Digital Research could not provide an 8086/88-based operating system for Seattle Computers 8086-based product at the time, yet the programmer needed CP/M-80 compatibility because that was the market standard.

Herb Johnson