Introduction to Operating Systems:History 2000 and Beyond

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2000 and Beyond

In the current decade, middleware, which is software that links two separate applications (often over a network), has become vital as applications are published on the World Wide Web and consumers use them via affordable, high-speed Internet connections over cable television lines and digital subscriber lines (DSL). Middleware is common in Web applications, in which a Web server (the application that sends data to the user’s Web browser) must generate content to satisfy a user’s request with the help of a database. The middleware acts as a courier to pass messages between the Web server and the database, simplifying communication between multiple different architectures. Web services encompass a set of related standards that can enable any two computer applications to communicate and exchange data via the Internet. A Web service communicates over a network to supply a specific set of operations that other applications can invoke. The data is passed back and forth using standard protocols such as HTTP, the same protocol used to transfer ordinary Web pages. Web services operate using open, text-based standards that enable components written in different languages and on different platforms to communicate. They are ready-to- use pieces of software on the Internet.

Web services will help drive the shift toward true distributed computing. For example, the online retailer Amazon.com allows developers to build online stores that search Amazon’s product databases and display detailed product information via Amazon.com Web Services (www.amazon.com/gp/aws/landing.html). The Google search engine also can be integrated with other functionality through the Google Web APIs (www.google.com/apis), which connect to Google’s indices of Web sites using Web services. We discuss Web services in more detail in Chapter 18, Distributed Systems and Web Services.

Multiprocessor and network architectures are creating numerous opportunities for research and development of new hardware and software design techniques. Sequential programming languages that specify one computation at a time are now complemented by concurrent programming languages, such as Java, that enable the specification of parallel computations; in Java the units of parallel computing are specified via threads. We discuss threads and the technique of multithreading in Chapter 4, Thread Concepts.

An increasing number of systems exhibit massive parallelism; they have large numbers of processors so that many independent parts of computations can be per- formed in parallel. This is dramatically different in concept from the sequential computing of the past 60 years; there are significant and challenging problems in developing the software appropriate for dealing with such parallelism. We discuss parallel computing architectures in Chapter 15, Multiprocessor Management.

Operating systems are standardizing user and application interfaces so that they are easier to use and support a greater number of programs. Microsoft has already merged the consumer and professional lines of its Windows operating sys- tem into Windows XP. In its next operating system (code-named Longhorn), Microsoft plans to integrate the formats of different types of files. This will, for example, allow users to search their systems for all files (documents, spreadsheets, e-mails, etc.) containing certain keywords. Longhorn will also include an enhanced 3D user interface, improved security and support for recordable digital versatile discs (DVDs).99, 100 Open-source operating systems, such as Linux, will become more widely used and will employ standard application programming interfaces (APIs) such as the Portable Operating System Interface (POSIX) to improve compatibility with other UNIX-based operating systems.

Computing on mobile devices, such as cell phones and PDAs, will become more common as mobile devices are equipped with increasingly powerful processors. Today, these devices are used for such functions as e-mail, Web browsing and digital imaging. Resource-intensive applications, such as full-motion video, will proliferate on these devices. Because mobile device resources are limited by the devices’ small size, distributed computing will play an even larger role, as PDAs and cell phones will request increasing amounts of data and processing power from remote computers.

Self Review

1. What technologies can be used to bridge the gap between different operating systems?

How would these technologies make it possible to execute the same application on multiple platforms?

2. Why is distributed computing useful for computations performed by mobile devices?

Ans: 1) Virtual machines and operating system emulators bridge the gap between different operating systems. Applications can be written once to use the functionality of the virtual machine or emulator. The virtual machines or emulators can be implemented to hide the representation of the underlying platform from the applications.

2) Distributed computing allows a mobile device to delegate jobs to other machines with more resources. The mobile device, having limited resources and battery life, can request data and processing power from larger computers across a network.

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