and debugging at the application layer is inherently simpler than programming at the OS layer. The benefit ere is to the os designer and implementors who can now write and debug os code faster and easier tha before. This benefits the user by having an operating system that is more reliable The second advantage stems from the ability to incorporate several different OS environments on top of the same micro-kernel. In this way, the computer acts as though it is running several operating systems. For example if both ms-dos and uniX coexisted on the same micro-kernel, the user could choose to run an ms-dos spreadsheet or word processor and communicate using UNIX network commands. The user has gained increased flexibility. 96.8 Industry Standards As computer technologies come into widespread use, users begin to desire standardization. Standardization allows a user to know that a program written to a standard will work without concern for which vendor supplies the programming environment. Operating systems are no exception to this general rule, and there are several standards, both industry standards and de facto standards, that apply. Porting software from one system to another, often an expensive proposition, becomes a trivial task Perhaps the most notable OS standard is POSIX, standard number 1003 [IEEE, 1990], sponsored by the IEEE Computer Society's Technical Committee on Operating Systems. POSIX is a family of standards based on the UNIX operating system that includes the system call interface, user-level ds, real-time extensions and networking extensions. The POSIX system call interface, 1003. 1, was adopted by the U.S. government verbatim as a Federal Information Processing Standard, FIPS 151. Many vendors conform to POSIX; thus, a program that conforms to this standard can be ported to many system platforms without change An example of a de facto standard is the X/Open Portability Guide(XPG)[X/Open, 1989. X/Open is not a standards-setting body but is a joint initiative by members of the business community to adopt and adapt existing standards into a consistent environment. The X/Open system interface and headers are based on POSIX 1003.1 but also include extensions to posix-defined interfaces as well as additional interfaces The importance of such standards is evidenced by the strong support of such organizations as the Open Software Foundation. OSF's OSF/1 operating system conforms to various POSIX standards. Where not super seded by POSIX, it also conforms to XPG and AT&Ts System V Interface Definition(SVID)[AT&T, 1985 Conforming to these standards is considered critical for the success of oSF/ Some might consider an operating system such as MS-DOS to be a de facto standard. While MS-DOS is in common use, however, it is proprietary software subject to change without notice. Defining a standard implies an open system on which vendors and users agree 96.9 Conclusions I have been hearing for the past 15 years about the demise of the operating system. It has been said over and over that the role of the OS will go away. So far, the only change has been to expand on the role the operating stem plays. One must remember that the operating system is not the user interface it portrays or the applications that run on it. It is, as it always has been, the manager of all resources on a computer system. While the interface to computers has changed and the use to which we apply computer technology has hanged, there will always be the need for an operating system. without question, the OS will change as well We have already seen kernel architectures begin to emerge from the research labs into commercial erating systems Distributed computing will become more widespread and force additional changes to the operating system. Regardless of the changes that come, it will always be the operating system on which all other prog Defining Terms Distributed computing: An environment in which multiple computers are networked together and the resources from more than one computer are available to a user. Those resources are accessed in a manner identical to accessing resources on a local computer system. e 2000 by CRC Press LLC© 2000 by CRC Press LLC and debugging at the application layer is inherently simpler than programming at the OS layer. The benefit here is to the OS designer and implementors who can now write and debug OS code faster and easier than before. This benefits the user by having an operating system that is more reliable. The second advantage stems from the ability to incorporate several different OS environments on top of the same micro-kernel. In this way, the computer acts as though it is running several operating systems. For example, if both MS-DOS and UNIX coexisted on the same micro-kernel, the user could choose to run an MS-DOS spreadsheet or word processor and communicate using UNIX network commands. The user has gained increased flexibility. 96.8 Industry Standards As computer technologies come into widespread use, users begin to desire standardization. Standardization allows a user to know that a program written to a standard will work without concern for which vendor supplies the programming environment. Operating systems are no exception to this general rule, and there are several standards, both industry standards and de facto standards, that apply. Porting software from one system to another, often an expensive proposition, becomes a trivial task. Perhaps the most notable OS standard is POSIX, standard number 1003 [IEEE, 1990], sponsored by the IEEE Computer Society’s Technical Committee on Operating Systems. POSIX is a family of standards based on the UNIX operating system that includes the system call interface, user-level commands, real-time extensions, and networking extensions. The POSIX system call interface, 1003.1, was adopted by the U.S. government verbatim as a Federal Information Processing Standard, FIPS 151. Many vendors conform to POSIX; thus, a program that conforms to this standard can be ported to many system platforms without change. An example of a de facto standard is the X/Open Portability Guide (XPG) [X/Open, 1989]. X/Open is not a standards-setting body but is a joint initiative by members of the business community to adopt and adapt existing standards into a consistent environment. The X/Open system interface and headers are based on POSIX 1003.1 but also include extensions to POSIX-defined interfaces as well as additional interfaces. The importance of such standards is evidenced by the strong support of such organizations as the Open Software Foundation. OSF’s OSF/1 operating system conforms to various POSIX standards. Where not super￾seded by POSIX, it also conforms to XPG and AT&T’s System V Interface Definition (SVID) [AT&T, 1985]. Conforming to these standards is considered critical for the success of OSF/1. Some might consider an operating system such as MS-DOS to be a de facto standard. While MS-DOS is in common use, however, it is proprietary software subject to change without notice. Defining a standard implies an open system on which vendors and users agree. 96.9 Conclusions I have been hearing for the past 15 years about the demise of the operating system. It has been said over and over that the role of the OS will go away. So far, the only change has been to expand on the role the operating system plays. One must remember that the operating system is not the user interface it portrays or the applications that run on it. It is, as it always has been, the manager of all resources on a computer system. While the interface to computers has changed and the use to which we apply computer technology has changed, there will always be the need for an operating system. Without question, the OS will change as well. We have already seen micro-kernel architectures begin to emerge from the research labs into commercial operating systems. Distributed computing will become more widespread and force additional changes to the operating system. Regardless of the changes that come, it will always be the operating system on which all other programs rely. Defining Terms Distributed computing: An environment in which multiple computers are networked together and the resources from more than one computer are available to a user. Those resources are accessed in a manner identical to accessing resources on a local computer system