Pilot is a single-user, multitasking

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

Xerox PARC Future Concepts division (formerly Palo Alto Research Center, PARC and Xerox PARC) is a research and development company in Palo Alto, California. It was founded in 1969 by Jacob E. "Jack" Goldman, chief scientist of Xerox Corporation, as a div ...

in early 1977. Pilot was written in the

Mesa A mesa is an isolated, flat-topped elevation, ridge, or hill, bounded from all sides by steep escarpments and standing distinctly above a surrounding plain. Mesas consist of flat-lying soft sedimentary rocks, such as shales, capped by a ...

programming language A programming language is a system of notation for writing computer programs. Programming languages are described in terms of their Syntax (programming languages), syntax (form) and semantics (computer science), semantics (meaning), usually def ...

, totalling about 24,000 lines of code.

Overview

Pilot was designed as a single user system in a highly networked environment of other Pilot systems, with interfaces designed for

inter-process communication In computer science, interprocess communication (IPC) is the sharing of data between running Process (computing), processes in a computer system. Mechanisms for IPC may be provided by an operating system. Applications which use IPC are often cat ...

(IPC) across the network via the Pilot stream interface. Pilot combined

virtual memory In computing, virtual memory, or virtual storage, is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a ver ...

and file storage into one subsystem, and used the manager/

kernel Kernel may refer to: Computing * Kernel (operating system), the central component of most operating systems * Kernel (image processing), a matrix used for image convolution * Compute kernel, in GPGPU programming * Kernel method, in machine learnin ...

architecture for managing the system and its resources. Its designers considered a non-preemptive multitasking model, but later chose a preemptive (run until blocked) system based on

monitors Monitor or monitor may refer to: Places * Monitor, Alberta * Monitor, Indiana, town in the United States * Monitor, Kentucky * Monitor, Oregon, unincorporated community in the United States * Monitor, Washington * Monitor, Logan County, West ...

. Pilot included a debugger, Co-Pilot, that could debug a frozen snapshot of the operating system, written to disk. A typical Pilot workstation ran 3 operating systems at once on 3 different disk volumes : Co-Co-Pilot (a backup debugger in case the main operating system crashed), Co-Pilot (the main operating system, running under co-pilot and used to compile and bind programs) and an inferior copy of Pilot running in a third disk volume, that could be booted to run test programs (that might crash the main development environment). The debugger was written to read and write variables for a program stored on a separate disk volume. This architecture was unique because it allowed the developer to single-step even operating system code with semaphore locks, stored on an inferior disk volume. However, as the memory and source code of the D-series Xerox processors grew, the time to checkpoint and restore the operating system (known as a "world swap") grew very high. It could take 60-120 seconds to run just one line of code in the inferior operating system environment. Eventually, a co-resident debugger was developed to take the place of Co-Pilot. Pilot was used as the operating system for the

Xerox Star The Xerox Star workstation, officially named Xerox Star 8010 Information System, is the first commercial personal computer to incorporate technologies that have since become standard in personal computers, including a bitmapped display, a window- ...

workstation.

Overview

See also

References

Further reading