V (operating system)
The operating system V (sometimes called V- system ) is an operating system with microkernel, which was developed at Stanford University under the direction of Professor David Cheriton in the 1980s by faculty and students in the Distributed Systems Group. V was the successor of the operating systems and Thoth Verax where Cheriton had previously worked.
Terminology of V
The original V- terminology used "process" for what is now commonly called thread, and "team" for what is now usually called a process that consists of multiple threads that share an address space. This article uses the modern terms.
The key concepts of multithreading and V are synchronous message exchange. In V, the communication between threads works with synchronous message exchange integral with short message length, can include the access rights for the receiver to parts of the address space of the sender before the reply read or write. The same interface for the exchange of messages between threads is both within a process, between threads of different processes on the same machine, as well as between threads in different machines, which are connected via a local Ethernet may be used. A thread that receives a message, it does not have to answer before he has received other messages; herein differs from the model in Ada rendezvous model.
A common pattern for use of the communication link for clients is to send a message with the request for service to a server. From the client side, this almost like a RPC (Remote Procedure Call) appears. The convenience of an automatic stub generator is missing, on the other hand, the client can pass a reference parameter, which is not possible via RPC. From the server side of the model differs more from RPC, because by default, all client requests are bundled on a server thread. The server may, however, explicitly to produce a replica of a thread to process client requests in parallel; If he does so, the server-side model is also almost like RPC.
V was never even an endpoint for Cheriton 's group; Instead, it was used as a vehicle for many different development projects in the area 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 all components necessary for operation included ( self- hosting). Many students operated V as the only operating system on their Sun or VAX diskless workstations. Compile could either V itself or on VAX Unix machines, the services offered in a more stable environment than the constantly changing development system.
Meanwhile, with the larger -Availability Linux and BSD Unix for PCs, it seems that experimental operating systems of this type with self- hosting have become rare, since there is little willingness to do so much work, only to find themselves with infrastructure to supply. V is almost forgotten today, but it has left traces in the sands of time: The little-known system window W takes its name partly because it first ran on the V operating system ( on the VGT graphics package ). And the well-known X Window System itself gets its name because its first version partially based on W. V also led to the desire for a " purer " microkernel on Apple computers, known as Vanguard, which added a number of improvements to the original system. Vanguard disappeared in a reorganization. In the late 1980s, the Tektronix VM700 TV monitor is designed in a V- network environment, and ran with a slightly modified version of the V operating system; this device is still manufactured and sold.