The Takeda Award 2001

4. Linux project

Summary
     In 1991, Linus Torvalds made the first version of his original Linux and released it on the Internet(14). Linux was the UNIX compatible computer operating system kernel. After that, many volunteers from around the world joined the Linux project to improve and debug Linux. Revised versions of Linux were also released with no charge to anyone who wanted to use it.
     The characteristic feature of Linux development is the introduction and promotion of a new development style(15) where many volunteers freely and directly join in improving and debugging the program whenever they want. Torvalds decides which contribution to accept and to be included in the next revision of Linux. This style did not produce competing versions of Linux and kept the uniformity of the operating systems kernel(16),(17). He released new versions frequently to distribute the results of debugging and other improvements. This frequent release of new versions made it possible to manage effectively the willing efforts of volunteers.
     This open-style computer software development resulted in voluntary, enthusiastic, and speedy improvements, and led to a high performance and high reliability operating system kernel.

Linux development progress
     In September 1991, Torvalds released the first version of Linux0.01. After that,Version 1.00 was released in 1994, which was the completion of the kernel. Version 2.0, released in 1996, made Linux a practical operating system(18).
     Torvalds plays the central role in Linux development. The worldwide volunteers develop by themselves a part of source code that they need and Torvalds decides which source code revisions to adopt with the help of a filtering process conducted by his supporting staff. Because of this development process, where any volunteers develop the programs they need, high quality programs can be obtained in a short time.
     The Linux specification was based on the UNIX standard specification POSIX. That means that Linux is a UNIX clone. But the source code of Linux is original and the Linux source code is freely open for anyone.

	The revision record of Linux is as follows(19),( 20).
	1991:	Torvalds started to develop Linux. Release of Version 0.01.
	1994:	Release of Version 1.00.
	1996:	Release of Version 2.0 for general use and Version 2.1.0 for development use.
	1999:	Release of Version 2.2.0 for general use and Version 2.3.0 for development use.
	1999:	Release of Version 2.2.0 for general use and Version 2.3.0 for development use.
	2001:	Release of Version 2.4.0 for general use.

     From Version 0.01 to 1.00, 119 revisions were released in 2 years and 5 months. From Version 1.00 to 2.0, 234 revisions were released in 2 years and 3 months. From 2.0 to 2.1.0, 21 revisions were released in 4 months. From 2.1.0 to 2.2.0, 142 revisions were released in 2 years and 4 months. From 2.2.0 to 2.3.0, 9 revisions were released in 4 months. From 2.3.0 to 2.4.0, 74 revisions were released in 1 year and 8 months. In the mostly frequent revision period in the years from 1994 to 1996, more than 10 revisions were release per month.

Feature of Linux distribution
     The user-friendly package, which contains installation software, network support software and utility programs as well as Linux itself, is prepared in CDROM or on a Web site. There are various types of distribution. Some distributions are provided at no charge by volunteers. Other distributions are commercially sold by companies. This distribution system promotes Linux while keeping the unity of Linux to guarantee compatibility.
     In the case of UNIX, the source code was made available through a for-fee license from AT&T. BSD code, developed in University of California in Berkeley, can also be obtained with a license. Using these source codes, each vendor prepared each commercial package after appropriate revision.
     In the UNIX standardization process, the specification like POSIX was promoted instead of the unification of the source code itself. The source code of the operating system kernel was dependent on each vendor. As a result, the source code was different in each vendor and the specification was different in its details. The UNIX operating systems cannot be guaranteed to be compatible with each other.
     When some trouble occurs during the running of an application program, the cause of the trouble cannot be analyzed because the vendors did not make the source code available. It is often impossible to determine the reason without the vendor's cooperation whether the trouble is in the application program or in the operating systems itself.
     Compared with the above-mentioned UNIX case, in the Linux case, each distribution contains the open source code, and compatibility with the unified Linux kernel is guaranteed. Technical support can be provided easily because of the open source code. The Linux license is provided at no charge. This no-charge license becomes a great advantage, especially when many machines are used or a large number of embedded systems are produced.

Worldwide usage of Linux and GNU software
     Linux was at first an operating system for stand-alone desktop computers, and afterwards was improved to support multiprocessor systems. Linux is widely spreading to be installed in various kinds of systems; super computers, large-scale systems, Internet terminals, cellular phones, and other embedded systems. The programmer who feels that a modification is necessary modifies the Linux source code. Other people can then use the resulting open source code.
     The Linux share is 25% (1.3 million) of the worldwide server operating system deliveries in 1999 and 7.8% of the Japanese server operating systems deliveries in 2000. This means Linux is the dominant server operating system. Because of their no-charge for operating systems itself, the market share based on value of sales is not meaningful. In any case, Linux has produced a very large market.
     GNU software and Linux have begun to be widely used in server and conventional computer systems, because of their excellent functionality and reliability and because of the low systems development cost. Recently, main computer makers have decided to develop the ability to install Linux in all kinds of their machines. In May 2001, IBM, Fujitsu, Hitachi and NEC agreed to develop an operating system for essential business systems such as bank teller systems, using Linux as a base. Besides the merits of Linux -- low cost, system stability, high network ability and system compatibility -- cooperation by these four companies makes it possible to reduce the development cost and to shorten the development period.