Pilot is a single-user,
multitasking operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
designed by
Xerox PARC
PARC (Palo Alto Research Center; formerly Xerox PARC) is a research and development company in Palo Alto, California. Founded in 1969 by Jacob E. "Jack" Goldman, chief scientist of Xerox Corporation, the company was originally a division of Xer ...
in early 1977. Pilot was written in the
Mesa
A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain. Mesas characteristically consist of flat-lying soft sedimentary rocks capped by a ...
programming language
A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language.
The description of a programming l ...
, totalling about 24,000
lines of code
Source lines of code (SLOC), also known as lines of code (LOC), is a software metric used to measure the size of a computer program by counting the number of lines in the text of the program's source code. SLOC is typically used to predict the am ...
.
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 (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 very ...
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 lea ...
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.
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 3rd 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 8010 Information System, is the first commercial personal computer to incorporate technologies that have since become standard in personal computers, including a raster graphics, bitmapped display ...
workstation.
See also
*
Timeline of operating systems
This article presents a timeline of events in the history of computer operating systems from 1951 to the current day. For a narrative explaining the overall developments, see the History of operating systems.
1950s
* 1951
** LEO I 'Lyons Elect ...
References
Further reading
*Horsley, T.R., and Lynch, W.C. Pilot: A software engineering case history. In Proc. 4th Int. Conf. Software Engineering, Munich, Germany, Sept. 1979, pp. 94-99.
External links
Pilot: An Operating System for a Personal Computer
{{operating-system-stub
Computer-related introductions in 1981
History of human–computer interaction
Proprietary operating systems
Window-based operating systems
Pilot
An aircraft pilot or aviator is a person who controls the flight of an aircraft by operating its directional flight controls. Some other aircrew members, such as navigators or flight engineers, are also considered aviators, because they a ...
1981 software