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1. The importance of computer in the information society and the role of operating systems
Recent rapid development of the information technology, especially computer and communication technologies, makes it possible to access the variety of worldwide data and, as a result, brings value to people. In the field of the information technology, software technology is essential as well as hardware technology. Application software and contents are familiar and useful to users. In addition to stand-alone computers,
there are many kinds of intelligent electronic products around us. The number and variety of processor-embedded systems is greater than that of stand-alone computers.
Information moves around the world, and it is desirable that it be accessible by people everywhere. It is desirable to have hardware and software for information technology used by all people who want them. In the information society, "being free/open," that is, being freely accessible and freely usable is an especially important
feature. "Being free/open" is also important in the development of computer software, especially system software, in order to gather and use the wisdom of many people.
In computer software systems, operating systems are usually used to make it easier to develop application software and contents. Operating
systems are the set of common and basic functions. Recently, even in small-scale embedded systems, which usually have severely limited memory capacity, it has become popular to use operating systems to improve the performance, reduce the cost and improve the reliability
of applications software.
For example, Windows, Mac OS and UNIX are operating systems, whereas word processors or spreadsheets are application software. Operating systems provide fundamental and common functions. Editors and compilers are examples of system software included as operating systems utilities to help application software development. Using operating systems, the application software developer can raise development efficiency and unify the software operation style. Thus, operating systems are the common and basic software systems, which are the key components
in the software in the infrastructure of the information society, computers and intelligent electronic products.
Operating system performance is dependent on the ability and personality of the programmer and operating systems differ in their speed and stability. Operating systems have been increasing in size and developing in functionality, along with improvements in hardware and other software. As a result, defects and low performance modules are more likely to
become incorporated in operating systems. Countermeasures to avoid these problems become very important and the operating system specifications must be optimized according to the hardware ability and the application field.
The tendency toward the increase in software size and development cost has contributed to the domination of proprietary software. The software production companies have prohibited users from changing programs or accessing their source code. However, any large-scale software cannot avoid the software troubles and bugs, which sometimes
seriously hurt computer performance. This kind of influence is most severe for operating systems or basic software. This has increased the demand for freedom to access and change the source code.
In the case of the small embedded systems such as for home electronic products or cellular phones, conventional operating systems are too large and are less useful because they lack real-time performance, which realizes high-speed and time-estimative operations for input signals from outside. Vendors distribute some kinds of specific operating systems for that purpose. But, problems arise as a result of differences between the specifications of these operating systems. Programmers are easily confused, application software is not as reusable, and, consequently, the software productivity is low. In the case of multi-processor systems with various kinds of processors, another problem arises because each operating system is only optimized to the specific type of processors, and unifying the operating systems results in a decrease of total performance.
This achievement, the origination and the advancement of open development models for system software in usual computers or in embedded systems, has resolved these problems. These three projects based on this concept are explained as follows. Figure 1 and Table 1 comparatively show the target field and the characteristics of the three projects. Figure 2 shows the concise development history of each.
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