Page 9 - DCAP103_Principle of operating system

Principles of Operating Systems

Notes
1.12 Summary
1.13 Keywords
1.14 Review Questions
1.15 Further Readings

Objectives

After studying this unit, you will be able to:
• Discuss history of operating systems

• Explain Unix-like structures in operating systems
• Understand microsoft windows family of operating systems

• Explain history of personal computers
• Discuss meaning of operating systems
• Explain supervisor and user mode

• Understand meaning of system calls and kernel
• Explain operating system operations and functions
• Understand types of operating system: RTOSs, multiprogramming, multitasking,
distributed systems, etc

Introduction

Modern general-purpose computers, including personal computers and mainframes, have an
operating system to run other programs, such as application software. Examples of operating
systems for personal computers include Microsoft Windows, Mac OS (and Darwin), Unix, and
Linux. The lowest level of any operating system is its kernel. This is the first layer of software
loaded into memory when a system boots or starts up. The kernel provides access to various
common core services to all other system and application programs. These services include,
but are not limited to: disk access, memory management, task scheduling, and access to other
hardware devices.

As the kernel, an operating system is often distributed with tools for programs to display and
manage a graphical user interface (although Windows and the Macintosh have these tools built
into the operating system), as well as utility programs for tasks such as managing files and
configuring the operating system. They are also often distributed with application software that
does not relate directly to the operating system’s core function, but which the operating system
distributor finds advantageous to supply with the operating system.
The delineation between the operating system and application software is not precise, and is
occasionally subject to controversy. From commercial or legal points of view, the delineation
can depend on the contexts of the interests involved. For example, one of the key questions in
the United States v. Microsoft antitrust trial was whether Microsoft’s web browser was part of
its operating system or whether it was a separable piece of application software.

Like the term “operating system” itself, the question of what exactly should form the “kernel” is
subject to some controversy, with debates over whether things like file systems should be included
in the kernel. Various camps advocate microkernels, monolithic kernels, and so on. Operating

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