V (operating system)
Encyclopedia
The V operating system (sometimes written V-System) is a microkernel
operating system
that was developed by faculty and students in the distributed systems group at Stanford University
from 1981 to 1988, led by Professors David Cheriton
and Keith A. Lantz. V was the successor to the Thoth and Verex operating systems that Cheriton had developed in the 1970s.
The key concepts in V are multithreading
and synchronous message passing. The original V terminology uses "process" for what is now commonly called a "thread", and "team" for what is now commonly called a "process
" consisting of multiple threads sharing an address space.
Communication between threads in V uses synchronous message passing, with short, fixed-length messages that can include access rights for the receiver to read or write part of the sender's address space before replying. The same message-passing interface is used both between threads within one process, between threads of different processes within one machine, and between threads on different machines connected by a local Ethernet
. A thread receiving a message is not required to reply to it before receiving other messages; this distinguished the model from Ada
rendezvous.
One common pattern for using the messaging facility is for clients to send messages to a server requesting some form of service. From the client side, this looks much like RPC (remote procedure call
). The convenience of an automatic stub generator was lacking, but on the other hand, the client can pass one parameter by reference, which is not possible with other RPC implementations. From the server side the model differs more from RPC, since by default all client requests are multiplexed onto one server thread. The server is free to explicitly fork threads to handle client requests in parallel, however; if this is done, the server-side model is much like RPC too.
V was never an end in itself for the Stanford group; rather, it was used as a vehicle for many different research projects in distributed operating systems and networking. Much like other operating system efforts of its day (such as Sprite), V was a complete system that was mostly self hosting. Many students ran V as the only operating system on their diskless SUN workstation
s or MicroVAX
workstations. Compiles could be done either on V itself or on VAX
Unix
machines that provided file service in a more stable environment than the ever-changing research system.
V did have some notable impacts. After the initial implementation on a single computer, protocol called the Versatile Message Transaction Protocol (VMTP) was developed to extend the send-receive-reply system call semantics over a local area network
.
The protocol included multicast support developed by Steve Deering
as a graduate student in the group. The Internet Protocol
layer to support this evolved into the IP multicast
standard.
The V system was used for graphical user interface
research. The Virtual Graphics Terminal Service (VGTS) provided a modular windowing system
for both local and remote applications.
The little-known W Window System
got its name because it was first hosted on the V operating system, and the better-known X Window System
in turn got its name because its first version was based partly on W. V also spawned another pure microkernel effort at Apple Computer
known as Vanguard, which added a number of improvements to the basic system. Vanguard later disappeared in a reorganization. The Tektronix VM700 television measurement instrument was developed in a networked V environment in the late 1980s and ran a lightly modified version of the V operating system; this device was still manufactured and sold for many years.
Microkernel
In computer science, a microkernel is the near-minimum amount of software that can provide the mechanisms needed to implement an operating system . These mechanisms include low-level address space management, thread management, and inter-process communication...
operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
that was developed by faculty and students in the distributed systems group at Stanford University
Stanford University
The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...
from 1981 to 1988, led by Professors David Cheriton
David Cheriton
David Ross Cheriton is a Canadian-born computer science professor at Stanford University who has investments in technology companies...
and Keith A. Lantz. V was the successor to the Thoth and Verex operating systems that Cheriton had developed in the 1970s.
The key concepts in V are multithreading
Thread (computer science)
In computer science, a thread of execution is the smallest unit of processing that can be scheduled by an operating system. The implementation of threads and processes differs from one operating system to another, but in most cases, a thread is contained inside a process...
and synchronous message passing. The original V terminology uses "process" for what is now commonly called a "thread", and "team" for what is now commonly called a "process
Process (computing)
In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system , a process may be made up of multiple threads of execution that execute instructions concurrently.A computer program is a...
" consisting of multiple threads sharing an address space.
Communication between threads in V uses synchronous message passing, with short, fixed-length messages that can include access rights for the receiver to read or write part of the sender's address space before replying. The same message-passing interface is used both between threads within one process, between threads of different processes within one machine, and between threads on different machines connected by a local Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
. A thread receiving a message is not required to reply to it before receiving other messages; this distinguished the model from Ada
Ada (programming language)
Ada is a structured, statically typed, imperative, wide-spectrum, and object-oriented high-level computer programming language, extended from Pascal and other languages...
rendezvous.
One common pattern for using the messaging facility is for clients to send messages to a server requesting some form of service. From the client side, this looks much like RPC (remote procedure call
Remote procedure call
In computer science, a remote procedure call is an inter-process communication that allows a computer program to cause a subroutine or procedure to execute in another address space without the programmer explicitly coding the details for this remote interaction...
). The convenience of an automatic stub generator was lacking, but on the other hand, the client can pass one parameter by reference, which is not possible with other RPC implementations. From the server side the model differs more from RPC, since by default all client requests are multiplexed onto one server thread. The server is free to explicitly fork threads to handle client requests in parallel, however; if this is done, the server-side model is much like RPC too.
V was never an end in itself for the Stanford group; rather, it was used as a vehicle for many different research projects in distributed operating systems and networking. Much like other operating system efforts of its day (such as Sprite), V was a complete system that was mostly self hosting. Many students ran V as the only operating system on their diskless SUN workstation
SUN workstation
The original SUN workstation was a modular computer system designed at Stanford University in the early 1980s.-History:The project name was derived from Stanford University Network, the campus network within Stanford....
s or MicroVAX
MicroVAX
The MicroVAX was a family of low-end minicomputers developed and manufactured by Digital Equipment Corporation . The first model, the MicroVAX I, was introduced in 1984...
workstations. Compiles could be done either on V itself or on VAX
VAX
VAX was an instruction set architecture developed by Digital Equipment Corporation in the mid-1970s. A 32-bit complex instruction set computer ISA, it was designed to extend or replace DEC's various Programmed Data Processor ISAs...
Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
machines that provided file service in a more stable environment than the ever-changing research system.
V did have some notable impacts. After the initial implementation on a single computer, protocol called the Versatile Message Transaction Protocol (VMTP) was developed to extend the send-receive-reply system call semantics over a local area network
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
.
The protocol included multicast support developed by Steve Deering
Steve Deering
Stephen Deering is a former Technical Leader at Cisco Systems, where he worked on the development and standardization of architectural enhancements to the Internet Protocol...
as a graduate student in the group. The Internet Protocol
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
layer to support this evolved into the IP multicast
IP Multicast
IP multicast is a method of sending Internet Protocol datagrams to a group of interested receivers in a single transmission. It is often employed for streaming media applications on the Internet and private networks. The method is the IP-specific version of the general concept of multicast...
standard.
The V system was used for graphical user interface
Graphical user interface
In computing, a graphical user interface is a type of user interface that allows users to interact with electronic devices with images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances and...
research. The Virtual Graphics Terminal Service (VGTS) provided a modular windowing system
Windowing system
A windowing system is a component of a graphical user interface , and more specifically of a desktop environment, which supports the implementation of window managers, and provides basic support for graphics hardware, pointing devices such as mice, and keyboards...
for both local and remote applications.
The little-known W Window System
W Window System
The W window system is a windowing system and precursor in name and concept to the modern X window system.W was originally developed at Stanford University by Paul Asente and Brian Reid for the V operating system...
got its name because it was first hosted on the V operating system, and the better-known X Window System
X Window System
The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...
in turn got its name because its first version was based partly on W. V also spawned another pure microkernel effort at Apple Computer
Apple Computer
Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...
known as Vanguard, which added a number of improvements to the basic system. Vanguard later disappeared in a reorganization. The Tektronix VM700 television measurement instrument was developed in a networked V environment in the late 1980s and ran a lightly modified version of the V operating system; this device was still manufactured and sold for many years.
External links
- V system documentation at bitsavers.org