chapter 13 operating systems: an overview
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Chapter 13 Operating Systems: An Overview. The Architecture of Computer Hardware and Systems Software: An Information Technology Approach 3rd Edition, Irv Englander John Wiley and Sons 2003. Bare Bones Computer System. Does not load instructions into main memory - PowerPoint PPT PresentationTRANSCRIPT
Chapter 13Operating Systems: An Overview
The Architecture of Computer Hardware and Systems Software:
An Information Technology Approach
3rd Edition, Irv Englander
John Wiley and Sons 2003
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Bare Bones Computer System
Does not load instructions into main memory
No user interface except for I/O routines provided with executing program
Is idle when waiting for user input No facility to store, retrieve, or
manipulate files No ability to control peripheral devices Can run only one program at a time
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Integrated Computer Environment
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Operating System – Basic Services
Programs that accept commands and requests from a user and a user’s program
Manages, loads, and executes programs
Manages hardware resources of the computer
Act as an interface between the user and the system
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Operating System – Additional Services
Provides interfaces for the user and the user’s programs
File support services I/O support services Means of starting the computer
Bootstrapping or booting the computer Initial Program Load (IPL)
Handles all interrupt processing Network services Provides tools and services for concurrent processing
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Additional Services Required by Concurrent Processing Allocates resources such as memory,
CPU time, and I/O devices to programs Protects users and programs from each
other and provides for inter-program communication
Provides feedback to the system administrators to permit performance optimization of the computer system
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OS Parts Memory Resident
Always loaded in memory Commonly called the kernel Contains essential services required by other parts of the operating
system and applications. Typically responsible for managing memory management, processes
and tasks, and secondary storage Memory Non-resident
Applications Infrequently used programs, software tools, and commands
Bootstrap program Diskless workstations or thin clients
Programs, including the OS, are located on another computer on the network
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Simplified Diagram of Operating System Services
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OS Degree of Activity
Interactive Also known as conversational systems
Batch processing User submits programs or jobs for
processing Little to no user interaction
Event driven Interrupts or service requests
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Hardware and the OS A hardware platform may support a variety of
operating systems An operating system may work on a variety of
platforms A standard operating system that works on different
hardware Provides program and file portability Enables user efficiency through recognizable interface Is implemented through a systems programming language
like C or C++ as opposed to assembly language
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Single Job Processing
Only one program is loaded into memory and executed
Example: MS-DOS Memory resident components
Command interface shell I/O routines, including BIOS File management system
User program in control
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OS Regains Control
When program is finished control is transferred back to the command interpreter
If the user’s program requests I/O The user wishes to stop the program
execution via a keyboard interrupt System malfunctions
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Single Job Processing
Disadvantages Lack of security
Programs can overwrite the resident OS Programs can write directly to I/O devices
System provides minimum memory management and no scheduling
CPU is often idle awaiting the completion of I/O operations
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Concurrent Operations
Multitasking (multiprogramming) vs. multiprocessing which implies multiple CPUs
Concurrent processing vs. simultaneous processing
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Achieving Multitasking
While one program is waiting for I/O to take place, another program is using the CPU to execute instructions.
Time-slicing. The CPU may be switched rapidly back and forth between different programs
Dispatching is the process of selecting which program to run at any given instant
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Sharing the CPU during I/O Breaks
I/O represents a large percentage of a typical program’s execution
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Time-sharing the CPU
Time slicing
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Services and Facilities Command processor File management system I/O control system Process control management and interprocess
communication Memory management Scheduling system Secondary storage management System protection management Network management, communication support, and
communication interfaces System Administration
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User Interface and Command Execution Services Types of user interfaces
CLI - Command Line Interface GUI - Graphical User Interface Menu environment
Shell User interface and command processor that interacts with
the kernel UNIX: C, Bourne and Korn shells
Command Languages IBM Mainframes – JCL MS Windows – BAT files, Windows Scripting Host UNIX – shell scripts
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File Management File - logical unit of storage Basic file management system provides
Directory structures for each I/O device Tools to copy and move files Information about each file in the system and the tools to
access that information Security mechanisms to protects files and control access
Additional file management features Backup, emergency retrieval and recovery File compression Transparent network file access auditing
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I/O Services andProcess Control Management I/O services
Startup configuration Device drives that implement interrupts and provide
other techniques for handling I/O Plug and play: hot swapping, hot plugging
Process control management A process is an executing program A thread is an individually executable part of a
process Interprocess messaging services
Example: a pipe in UNIX or DOS that is a temporary software connection between two programs or commands
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Memory Management
Keeps track of memory Identifies programs loaded into memory Amount of space each program uses Available remaining space Prevents programs from reading and writing
memory outside of their allocated space Maintains queues of waiting programs Allocates memory to programs that are next
to be loaded Deallocates a program’s memory space upon
program completion
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Scheduling High-level scheduling
Placed in queue based on level of priority and eventually executed
Dispatching Actual selection of processes that will be executed at any given
time Preemptive – uses clock interrupts Non-preemptive – program voluntarily gives up control
Context switching Transfer control to the process that is being dispatched Nonpreemptive: program voluntarily gives up control Preemptive: uses clock interrupt for multitasking
Processing requirements CPU vs. I/O bound
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Secondary Storage and Security
Secondary storage management Optimizes completion of I/O tasks for efficient disk
usage Combination of hardware and software
Security and protection services Protect OS from users Protect users from other users Prevent unauthorized entry to system Prevent unauthorized system use by authorized
users
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Network and Communication Services
TCP-IP protocol suite Locate and connect to other computers Access files, I/O devices, and programs from
remote systems Support distributed processing
Network Applications Email, remote login, Web services, streaming
multimedia, voice over IP telephony, VPN Interface between communication software
and OS I/O control system that provides network access
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System Administration Support
System configuration and setting group configuration policies
Adding and deleting users
Modifying user privileges
System security Files systems
management
Network administration Backups Software installations
and upgrades OS installations
(system generation), patches, and upgrades
System tuning and optimization
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Monolithic Kernel
Drawback: stability and integrity
Examples: UNIX Windows NT
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Hierarchical
Requests passthrough intermediatelayers
Examples Multics Data General
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Microkernel
Minimum essential functionality Client-server system on same system
Clients request services from microkernel which passes message onto appropriate server
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Mach OS Kernel
Microkernel implementation Includes
Message passing Interrupt processing Virtual memory management Scheduling Basic set of I/O drivers
Macintosh OS X, IBM AIX on RS/6000
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Types of Operating Systems
Single user, single tasking Single user, multitasking Multi-user, multitasking Distributed systems
Processing power distributed among computers in a cluster or network
Network servers Real-time systems Embedded systems
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Bootstrapping
Execution begins with bootstrap loader (mini-loader, IPL) stored in ROM
Looks for OS program in a fixed location Loads OS into RAM Transfers control to starting location of
OS Loader program in OS used to load and
execute user programs
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Bootstrapping
Cold vs.warm boot(does not retest the system)