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Operating Systems

Lecture 05:

VMs, OS examples, Processes

Today

• Announcements:

• Operating Systems Overview:

• Virtual Machines
• Windows vs. Unix vs. Linux: study cases
• Processes (Chapter 3)

Virtual

Machine

Concept

Process Virtual Machines

Traditional UNIX Systems

• Were developed at Bell Labs and became operational on a PDP-7 in 1970
• Incorporated many ideas from Multics
• PDP-11was a milestone because it first showed that UNIX would be an OS for all computers
• Next milestone was rewriting UNIX in the programming language C
  • demonstrated the advantages of using a high-level language for system code
• Was described in a technical journal for the first time in 1974
• First widely available version outside Bell Labs was Version 6 in 1976
• Version 7, released in 1978 is the ancestor of most modern UNIX systems
• Most important of the non-AT&T systems was UNIX BSD (Berkeley Software Distribution)

Modern UNIX Kernel

LINUX Overview

• Started out as a UNIX variant for the IBM PC
• Linus Torvalds, a Finnish student of computer science, wrote

the initial version

• Linux was first posted on the Internet in 1991
• Today it is a full-featured UNIX system that runs on several

platforms

• Is free and the source code is available
• Key to success has been the availability of free software

packages

• Highly modular and easily configured

Linux Kernel Components

Microsoft Windows Overview

 MS-DOS 1.0 released in 1981  4000 lines of assembly language source code  ran in 8 Kbytes of memory  used Intel 8086 microprocessor

 Windows 3.0 shipped in 1990  16-bit  GUI interface  implemented as a layer on top of MS-DOS

 Windows 95  32-bit version  led to the development of Windows 98 and Windows Me

 Windows NT (3.1) released in 1993  32-bit OS with the ability to support older DOS and Windows applications as well as provide OS/2 support

 Windows 2000  included services and functions to support distributed processing  Active Directory  plug-and-play and power- management facilities

 Windows XP released in 2001  goal was to replace the versions of Windows based on MS-DOS with an OS based on NT  Windows Vista shipped in 2007  Windows Server released in 2008  Windows 7 shipped in 2009, as well as Window s Server 2008 R  Windows Azure  targets cloud computing

Kernel-Mode Components of

Windows

• Executive
  • contains the core OS services
• Kernel
  • controls execution of the processors
• Hardware Abstraction Layer (HAL)
  • maps between generic hardware commands and responses and those unique to a specific platform
• Device Drivers
  • dynamic libraries that extend the functionality of the Executive
• Windowing and Graphics System
  • implements the GUI functions

User-Mode Processes

• Four basic types are supported by Windows:

Special System • user-mode services needed to manage the system Processes

• the printer spooler, event logger, and user-mode components Service Processes that cooperate with device drivers, and various network services

Environment • provide different OS personalities (environments) Subsystems

• executables (EXEs) and DLLs that provide the functionality users User Applications run to make use of the system

Summary Chapter 2

• Operating system objectives

and functions:

• convenience, efficiency, ability to evolve
• user/computer interface
• resource manager
• Evolution: serial processing,

simple batch systems, multiprogrammed batch systems, time sharing systems

• Concepts:
  • Process
  • Memory management: real address, virtual address
• OS structures: monolithic, microkernel, object-oriented
• Virtual machines: virtualization
• Examples:
  • Microsoft Windows/Windows 7
  • UNIX/Linux systems

Chapter 3: Processes