Plan 9 is a computing environment physically distributed across many machines. The distribution itself is transparent to most programs giving both users and administrators wide latitude in configuring the topology of the environment. Two properties make this possible: a per process group name space and uniform access to all resources by representing them as files. 1.

This paper presents the design of ####################### (DVDs). DVDs are the mechanism used by the Netstation Project to provide secure shared access to network-attached peripherals distributed in an untrusted network environment. DVDs improve Input/Output efficiency by allowing user processes to perform I/O operations directly from devices without intermediate transfer through the controlling operating system kernel. The security enforced at the device through the DVD mechanism includes resource boundary checking, user authentication, and restricted operations, e.g., read-only access. To illustrate the application of DVDs, we present the interactions between a network-attached disk and a file system designed to exploit the DVD abstraction. We further discuss third-party transfer as a mechanism intended to provide for efficient data transfer in a typical NAP environment. We show how DVDs facilitate third-party transfer, and provide the security required in a more open network environment.

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le application-specific use of I/O devices. The architecture is applied to several representative classes of device including network interfaces, network connected peripherals, disk drives and framestores. Of these, disks and framestores are of particular interest since they must be shared at a very fine granularity but have traditionally been presented to the application via a window system or file-system with a high-level and coarse-grained interface. A device driver for the framestore is presented which abstracts the device at a low level and is therefore able to provide each client with guaranteed bandwidth to the framebuffer. The design and implementation of a novel client-rendering window system is then presented which uses this driver to enable rendering code to be safely migrated into a shared library within the client. A low-level abstraction of a standard disk drive is also described which efficiently supports a wide variety of file systems, and other applications requiring

It is difficult to build user interfaces that must be distributed over a set of dynamic and heterogeneous I/O devices. This difficulty increases when we want to split, merge, replicate, and relocate the UI across a set of heterogeneous devices, without the application intervention. Furthermore, using generic tools, e.g. to search for UI compoments or to save/restore them, is usually not feasible. We follow a novel approach for building UIs that overcomes these problems: Using distributed file systems that export widgets to applications. In this paper we describe Omero, a UI server built along this line for the Plan B Operating System.

Plan 9 from Bell Labs has recently been converted from ASCII to an ASCIIcompatible variant of Unicode, a 16-bit character set. In this paper we explain the reasons for the change, describe the character set and representation we chose, and present the programming models and software changes that support the new text format. Although we stopped short of full internationalization---for example, system error messages are in Unixese, not Japanese---we believe Plan 9 is the first system to treat the representation of all major languages on a uniform, equal footing throughout all its software. Introduction The world is multilingual but most computer systems are based on English and ASCII. The release of Plan 9 [Pike90], a new distributed operating system from Bell Laboratories, seemed a good occasion to correct this chauvinism. It is easier to make such deep changes when building new systems than by refitting old ones. The ANSI C standard [ANSIC] contains some guidance on the matter of `wid...

Plumbing is a new mechanism for inter-process communication in Plan 9, specifically the passing of messages between interactive programs as part of the user interface. Although plumbing shares some properties with familiar notions such as cut and paste, it offers a more general data exchange mechanism without imposing a particular user interface.