Chapter 4 - DSpace at Waseda University

9
Chapter 2
functions via microprocessors. An early version of embedded systems was very simple. It
was built into an 8bit/16bit controller and it still has been used. As recently embedded system
industries are using in more powerful microprocessors and digital signal processing (DSP)
chips. It is necessary to show embedded OSes in order to control these large systems.
Early embedded systems operated by sequential program without OS, and it was out of
sequential program when occurred interrupts. Therefore, there was no necessity of using OS
and it was wasted system resources. However, recently the embedded system is larger than
before and it is to increase the system complexity by networks and multimedia, etc. Therefore
embedded system is hard to operate sequential program. These changes cause the necessity of
OS in embedded systems and also its system cannot ignore real-time characteristic, therefore,
embedded systems the used real-time OS. The products that adapted the real-time OS are
more increasing now. In the field, many embedded systems use real-time OSes according to
its purposes.
2.2 Linux Kernel
Linux is a member of the large family of Unix-like operating systems. A relative newcomer
experiencing sudden spectacular popularity starting in the late 1990s, Linux joins such well
known commercial Unix operating systems as System V. Linux was initially developed by
Linus Torvalds in 1991 as an operating system for IBM-compatible personal computers
based on the Intel 80386 microprocessor. Linus remains deeply involved with improving
Linux, keeping it up to date with various hardware developments and coordinating the
activity of hundreds of Linux developers around the world. The Linux kernel is located in