Operating System 2 Overview

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Operating System 2 Overview
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• OPERATING SYSTEM OBJECTIVES AND FUNCTIONS

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• An OS is a program that controls the execution of
  application programs and acts as an interface
  between applications and the computer hardware.
  Objectives
• Convenience
• Efficiency
• Ability to evolve

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• Briefly, the OS typically provides services in
  the following areas
• Program development
• Program execution
• Access to I/O devices
• Controlled access to files
• System access
• Error detection and response
• Accounting

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• THE EVOLUTION OF OPERATING SYSTEMS

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• Serial Processing
• Simple Batch Systems
• Multiprogrammed Batch Systems
• Time-Sharing Systems

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• Serial Processing
• With the earliest computers, from the late 1940s
  to the mid-1950s, the programmer interacted
• directly with the computer hardware there was no
  OS.These computers were run
• from a console consisting of display lights,
  toggle switches, some form of input device,
• and a printer. Programs in machine code were
  loaded via the input device (e.g., a card
• reader). If an error halted the program, the
  error condition was indicated by the lights. If
• the program proceeded to a normal completion, the
  output appeared on the printer.

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• Simple Batch Systems

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• Multiprogrammed batch system

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• Time sharing
• single user was inefficient, a large group of
  users together were not.
• the "state" of each user and their programs would
  have to be kept in the machine, and then switched
  between quickly. Ex
• NEW to name and begin writing a program
• OLD to retrieve a previously named program
• LIST to display the current program
• SAVE to save the current program
• RUN to execute the current program

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Five major theoretical advances

• 1. Processes
• A program in execution
• An instance of a program running on a computer
• The entity that can be assigned to and executed
  on a processor
• A unit of activity characterized by a single
  sequential thread of execution, a current state,
  and an associated set of system resources
• Three major lines of computer system development
  created problems in timing and synchronization
  that contributed to the development of the
  concept of the processmultiprogramming batch
  operation, time sharing, and real-time
  transaction systems
• problems Improper synchronization, Failed
  mutual exclusion, Nondeterminate program
  operation, Deadlocks

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Five major theoretical advances

• 2. Memory management
• Process isolation
• Automatic allocation and management
• Support of modular programming
• Support of modular programming
• Long-term storage

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Cont..

• 3. Information protection and security
• Availability
• Confidentiality
• Data integrity
• Authenticity
• 4. Scheduling and resource management\
• Fairness
• Differential responsiveness
• Efficiency
• 5. System structure

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Different approaches on os

• Microkernel architecture
• Multithreading
• Symmetric multiprocessing
• Distributed operating systems
• Object-oriented design

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MICROSOFT WINDOWS OVERVIEW
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TRADITIONAL UNIX SYSTEMS
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• Modern Unix Linux

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• As UNIX evolved, the number of different
  implementations proliferated, each providing
  some useful features. There was a need to
  produce a new implementation that unified many
  of the important innovations, added other modern
  OS design fetures, and produced a more modular
  architecture.

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System calls The system call is the means by
which a process requests a specific kernel
service. There are several hundred system calls,
which can be roughly grouped into six categories
filesystem, process, scheduling, interprocess
communication, socket (networking), and
miscellaneous.Table 2.7 defines a few examples in
each category.
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System calls The system call is the means by
which a process requests a specific kernel
service. There are several hundred system calls,
which can be roughly grouped into six categories
filesystem, process, scheduling, interprocess
communication, socket (networking), and
miscellaneous.Table 2.7 defines a few examples in
each category.
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