V (operating system)

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V
developer David Cheriton et al.
License (s) unknown
Kernel Microkernel
Architecture (s) Sun , MicroVAX, et al
compatibility experimentally, parts taken over into other systems
Others Development stopped

V (sometimes called V-System ) is an operating system with microkernel , which in the 1980s by faculty and students in the Distributed Systems Group of Stanford University , led by Professor David Cheriton was developed. V was the successor to the Thoth and Verax operating systems that Cheriton had previously worked on.

Terminology of V

The original V terminology used “process” for what is now commonly called a thread , and “team” for what is now commonly called a process consisting of several threads that share an address space . This article uses modern terms.

properties

The key concepts of V are multithreading and synchronous message exchange . In V, the communication between threads works with synchronous message exchange with short messages of fixed length, which can contain access rights for the recipient in order to be able to read or write parts of the address space of the sender before responding. The same message exchange interface is used between threads within a process, between threads in different processes on one machine, and between threads on different machines that are connected via local Ethernet . A thread that receives a message does not have to reply to it before it has received other messages; this is where the model differs from the rendezvous model in Ada .

A common pattern for clients to use messaging is to send a message to a server requesting a service. From the client side, this appears almost like an RPC ( Remote Procedure Call ). The convenience of an automatic stub generator is missing, on the other hand the client can transfer reference parameters, which is not possible via RPC. From the server side, the model differs more from RPC, since by default all client requests are bundled on one server thread. However, the server can expressly create a copy of a thread in order to process client requests in parallel; If it does, the server-side model is also almost like RPC.

use

V was never itself an end point for Cheriton's group; Instead, it was used as a vehicle for many different development projects in the field of distributed operating systems and network technology . Similar to the efforts of other operating systems of its time ( Sprite etc.), V was a complete system that essentially comprised all the components necessary for operation ( self-hosting ). Many students ran V as the only operating system on their Sun or VAX diskless workstations . You could compile either on V itself or on VAX Unix machines, which offered file services in a more stable environment than the constantly changing development system.

aftermath

Meanwhile, with the greater availability of Linux and BSD Unix for PCs, it seems that experimental operating systems of this type with self-hosting have become rare, as there is little willingness to do so much work just to keep infrastructure up to date supply. V is almost forgotten today, but it has left its mark on the sands of time: The little-known window system W got its name partly because it first ran on the V operating system (on the VGTS graphics package ). And the well-known X Window System itself got its name because its first version was partly based on W. V also led to the quest for a "cleaner" microkernel on Apple computers, known as Vanguard , which added a number of improvements to the original system. Vanguard disappeared as part of a reorganization. In the late 1980s, the Tektronix VM700 TV test tool was developed in a V-network environment and ran a slightly modified version of the V operating system; this device is still being manufactured and sold.

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