Figure 12 Schematic of a virtual machine 111 Operating System Environments 2004

Figure 12 schematic of a virtual machine 111

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Figure 1.2 Schematic of a virtual machine. 1.11 Operating System Environments
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2004 Deitel & Associates, Inc. All rights reserved. 1.12 Operating System Components and Goals Computer systems have evolved Early systems contained no operating system, Later gained multiprogramming and timesharing machines Personal computers and finally truly distributed systems Filled new roles as demand changed and grew
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2004 Deitel & Associates, Inc. All rights reserved. 1.12.1 Core Operating System Components User interaction with operating system Often, through special application called a shell – Kernel Software that contains core components of operating system Typical operating system components include: Processor scheduler Memory manager I/O manager Interprocess communication (IPC) manager File system manager
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2004 Deitel & Associates, Inc. All rights reserved. 1.12.1 Core Operating System Components Multiprogrammed environments now common Kernel manages the execution of processes Program components which execute independently but use single memory space to share data are called threads. To access I/O device, process must issue system call Handled by device driver Software component that interacts directly with hardware Often contains device-specific commands
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2004 Deitel & Associates, Inc. All rights reserved. 1.12.2 Operating System Goals Users expect certain properties of operating systems – Efficiency – Robustness – Scalability – Extensibility – Portability – Security – Protection – Interactivity – Usability
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2004 Deitel & Associates, Inc. All rights reserved. 1.13 Operating System Architectures Today’s operating systems tend to be complex Provide many services Support variety of hardware and software Operating system architectures help manage this complexity Organize operating system components Specify privilege with which each component executes
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2004 Deitel & Associates, Inc. All rights reserved. 1.13.1 Monolithic Architecture Monolithic operating system Every component contained in kernel Any component can directly communicate with any other Tend to be highly efficient Disadvantage is difficulty determining source of subtle errors
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2004 Deitel & Associates, Inc. All rights reserved. Figure 1.3 Monolithic operating system kernel architecture. 1.13.1 Monolithic Architecture
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2004 Deitel & Associates, Inc. All rights reserved. 1.13.2 Layered Architecture Layered approach to operating systems Tries to improve on monolithic kernel designs Groups components that perform similar functions into layers Each layer communicates only with layers immediately above and below it Processes’ requests might pass through many layers before completion System throughput can be less than monolithic kernels Additional methods must be invoked to pass data and control
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2004 Deitel & Associates, Inc. All rights reserved.
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