Introduction to Operating Systems:History The 1990s

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The 1990s

Hardware performance continued to improve exponentially in the 1990s.69 By the end of the decade,a typical personal computer could execute several hundred mil- lion instructions per second (MIPS) and store over a gigabyte of information on a hard disk; some supercomputers could execute over a trillion operations per second.70 Inexpensive processing power and storage enabled users to execute large, complex programs on personal computers and enabled small- to mid-size companies to use these economical machines for the extensive database and processing jobs that were once delegated to mainframe systems. Falling technology costs also led to an increase in the number of home computers, which were used both for work and for entertainment.

In the 1990s, the creation of the World Wide Web led to an explosion in the popularity of distributed computing. Originally, operating systems performed isolated resource management inside a single computer. With the creation of the World Wide Web and increasingly fast Internet connections, distributed computing became commonplace among personal computers. Users could request data stored at remote locations or request that programs run on distant processors. Large organizations could use distributed multiprocessors (i.e., networks of computers containing more than one processor) to scale resources and increase efficiency.71 Distributed applications, however, were still limited by the fact that communication over a network occurred at relatively slow speeds compared to the internal processing speeds of individual computers. Distributed computing is discussed in detail in Chapter 17, Introduction to Distributed Systems, and Chapter 18, Distributed Sys- tems and Web Services.

As demand for Internet connections grew, operating system support for net- working tasks became standard. Users at home and in organizations increased productivity by accessing the resources on networks of computers. However, increased connectivity led to a proliferation of computer security threats. Operating system designers developed techniques to protect computers from these malicious attacks. Ever more sophisticated security threats continued to challenge the computer industry’s ability to counter such attacks.

Microsoft Corporation became dominant in the 1990s. In 1981, Microsoft released the first version of its DOS operating system for the IBM personal computer. In the mid-1980s, Microsoft developed the Windows operating system, a graphical user interface built on top of the DOS operating system. Microsoft released Windows 3.0 in 1990; this new version featured a user-friendly interface and rich functionality. The Windows operating system became incredibly popular after the 1993 release of Windows 3.1, whose successors, Windows 95 and Windows 98, virtually cornered the desktop operating system market by the late 90s. These operating systems, which borrowed from many concepts (such as icons, menus and windows) popularized by early Macintosh operating systems, enabled users to navigate multiple concurrent applications with ease. Microsoft also entered the corporate operating system market with the 1993 release of Windows NT, which quickly became the operating system of choice for corporate workstations.72 Windows XP, which is based on the Windows NT operating system, is discussed in Chapter 21, Case Study: Windows XP.

Object Technology

Object technology became popular in many areas of computing, as the number of applications written in object-oriented programming languages, such as C++ or Java, increased steadily. Object concepts also facilitated new approaches to computing. Each software object encapsulates a set of attributes and a set of actions. This allows applications to be built with components that can be reused in many applications, reducing software development time. In object-oriented operating systems (OOOS), objects represent components of the operating system and system resources.73 Object-oriented concepts such as inheritance and interfaces were exploited to create modular operating systems that were easier to maintain and extend than operating systems built with previous techniques. Modularity facilitates operating system support to new and different architectures. The demand for object integration across multiple platforms and languages led to support for objects in programming languages such as Sun’s Java and Microsoft’s .NET languages (e.g., Visual Basic .NET, Visual C++ .NET and C#).

Open-Source Movement

Another development in the computing community (particularly in the area of operating systems) during the 1990s was the movement toward open-source software. Most software is created by writing source code in a high-level programming language. However, most commercial software is sold as object code (also called machine code or binaries)—the compiled source code that computers can under- stand. The source code is not included, enabling vendors to hide proprietary information and programming techniques. However, free and open-source software became increasingly common in the 1990s. Open-source software is distributed with the source code, allowing individuals to examine and modify the software before compiling and executing it. For example, the Linux operating system and the Apache Web server, both of which are free and open source, were downloaded and installed by millions of users during the 1990s, and the number of downloads is increasing rapidly in the new millennium.74 Linux, created by Linus Torvalds (see the Biographical Note, Linus Torvalds), is discussed in Chapter 20, Case Study: Linux.

In the 1980s, Richard Stallman, a software developer at MIT, launched a project to recreate and extend most of the tools for AT&T’s UNIX operating sys- tem and to make the code available at no charge. Stallman (see the Biographical Note, Richard Stallman) founded the Free Software Foundation and created the GNU project—which is a recursive name that stands for “GNU’s Not UNIX”— because he disagreed with the concept of selling the permission to use software.75 He believed that granting users the freedom to modify and distribute software would lead to better software, driven by user needs instead of personal or corporate profit. When Linus Torvalds created the original version of the Linux operating sys- tem, he employed many of the tools published by GNU for free under the General Public License (GPL). The GPL, published online at www.gnu.org/licenses/ gpl.html, specifies that anyone can freely modify and redistribute software under its license, provided that the modifications are clearly indicated and any derivative of the software is also distributed under the GPL.76 Although most GPL-licensed software is available free of charge, the GPL requires only that its software be free in the sense that users can freely modify and redistribute it. Therefore, vendors can charge a fee for providing GPL-licensed software and its source code, but cannot

Biographical Note

Linus Torvalds

Linus Torvalds was born in 1969 in Helsinki, Finland. As a child he taught himself how to program by playing with a Commodore VIC-20. In 1988 he entered the University of Helsinki to study computer science. While there, he wrote a UNIX clone based on Professor Andrew Tanenbaum’s Minix to run on his new PC.77, 78 In 1991 he completed the first version of the basic Linux kernel, which ran on the Intel 80386 processor.79 He distributed Linux under the GNU

Public License (GPL)80 as open- source code and gladly accepted additions, corrections and free programs from other programmers.81,82 By 1994 Linux had accrued enough applications to be a complete, usable operating system, and version 1.0 was released.83 Programmers and professors using UNIX on large systems liked Linux because it brought the features and power of UNIX to inexpensive desktop systems for free.84, 85

Torvalds is currently a fellow of the Open Source Development Labs (OSDL), which funds his full- time work on the kernel. He con- tinues to lead the open-source Linux project, managing changes and releasing new versions of the kernel.86, 87 Linux has become one of the largest and best-known open-source developments in com- puting history and has become particularly successful in the server market. Linux is discussed in Chapter 20, Case Study: Linux.

prevent end users from modifying and redistributing them. In the late 90s, the Open Source Initiative (OSI) was founded to protect open-source software and promote the benefits of open-source programming (see www.opensource.org).

Open-source software facilitates enhancements to software products by per- mitting anyone in the developer community to test, debug and enhance applications. This increases the chance that subtle bugs, which could otherwise be security risks or logic errors, are caught and fixed. Also, individuals and corporations can modify the source to create custom software that meets the needs of a particular environment. Many open-source software vendors remain profitable by charging individuals and organizations for technical support and customizing software.88 Though most systems in the 1990s still ran proprietary operating systems, such as IBM mainframe operating systems, UNIX systems, Apple’s Macintosh and

Biographical Note

Richard Stallman

Richard Stallman was the original developer of the GNU project, started in the 1980s to create free software. Stallman graduated from Harvard in 1974 with a degree in Physics.89 While at Harvard, he worked at the MIT Artificial Intelligence Lab. After graduating, he continued at the lab, where he and his colleagues worked with shared software.90 The idea was that someone receiving someone else’s executable program would also receive its source code. This was advantageous because a programmer could add more functionality to someone else’s program.91 Stall- man’s specific job was to modify and improve the ITS operating system the lab used. However, as the 1980s arrived, there was little shared software.92 The lab’s new operating system was not shared. Stallman became frustrated with operating systems, drivers, and the like, that he could no longer modify.93 In 1984 he left the MIT Artificial Intelligence Lab to work on a new shared operating sys- tem, which he called GNU (GNU’s Not UNIX).94 As interest in Stallman’s GNU project grew, he created the Free Software Foundation (FSF) in 1985 to promote free software and continue to develop the GNU operating system.95 Stallman and his associates at FSF created a number of GNU programs, including GNU Emacs (a text editor), GCC (a C compiler) and GDB (a debugger), to name a few.96 In 1992 Stallman used the Linux kernel to complete his system. The system, known as GNU/Linux, is a fully functional operating system and includes a variety of pro- grams.97 Stallman has received numerous awards and recognition for his work, including the Grace Hopper Award, MacArthur Foundation Fellowship, the Electric Frontier Foundation Pioneer Award, the Yuri Rubinksi Award, the Takeda Award, election to the National Academy of Engineering and two honorary doctorates from the Institute of Technology in Sweden and the University of Glasgow. Stallman continues to promote the free software cause and speaks about free software all over the world.98

Microsoft’s Windows, open-source operating systems, such as Linux, FreeBSD and OpenBSD, became viable competition. In the future, they will undoubtedly con- tinue to gain ground on proprietary solutions as a result of product improvement, industry standardization, interoperability, product customization and cost savings.

In the 1990s, operating systems became increasingly user friendly. The GUI features that Apple built into its Macintosh operating system in the 1980s became more sophisticated in the 1990s. “Plug-and-play” capabilities were built into operating systems, enabling users to add and remove hardware components dynamically without manually reconfiguring the operating system. Operating systems also maintained user profiles—serving authentication needs and enabling per-user customization of the operating system interface.

Self Review

1. How did object-oriented technology affect operating systems?

2. What are some of the benefits of open-source development?

Ans: 1) Operating systems designers could reuse objects when developing new components. Increased modularity due to object-oriented technology facilitated operating system support for new and different architectures. .

2) Open-source software can be viewed and modified by anyone in the software development community. Because these people constantly test, debug and use the software, there is a greater chance that bugs will be found and fixed. Also, open-source software enables users and organizations to modify a program to meet their particular needs.

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