About: Tell us about working on the floppy disk.
Richard Mateosian The disks were 8 inches in diameter and had a capacity of 200K. Since they were so large, we divided them into four partitions, each of which we regarded as a separate hardware device -- analogous to a cassette drive (our other main peripheral storage device). We used floppy disks and cassettes mostly as paper tape replacements, but we also appreciated and exploited the random access nature of disks.
Our operating system had a set of logical devices (source input, listing output, error output, binary output, etc.) and a mechanism for establishing a correspondence between these and the hardware devices. Our applications programs were versions of HP assemblers, compilers, and so forth, modified (by us, with HP's blessing) to use our logical devices for their I/O functions.
The rest of the operating system was basically a command monitor. The commands had mainly to do with file manipulation. There were some conditional commands (like IF DISK) for use in batch files. The entire operating system and all of the application programs were in HP 2100 series assembly language.
The underlying system software, which we wrote from scratch, was interrupt driven, so we could support simultaneous I/O operations, such as keying in commands while the printer was running or typing ahead of the 10 character per second teletype. The structure of the software evolved from Gary Hornbuckle's 1968 paper "Multiprocessing Monitor for Small Machines" and from PDP8-based systems, I worked on at Berkeley Scientific Laboratories (BSL) in the late 1960s. The work at BSL was largely inspired by the late Rudolph Langer, who improved significantly on Hornbuckle's model.
