May 2013 Archive


System Calls for Directory Management
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System Calls for Directory Management

Now we will consider some system calls that relate more to directories or the file system as a whole, rather than just to one particular file as in the previous section. The first two calls, mkdir and rmdir, create and remove

Miscellaneous System Calls
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Miscellaneous System Calls

Various other system calls exist as well. We will consider just four of them here. The chdir call changes the current working directory. After the call

The Windows Win32 API
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The Windows Win32 API

We have, so far, focused mostly on UNIX. Now it is time to briefly describe Windows. Windows and UNIX differ in a primary way in their respective programming models. A UNIX program contains code that does

OPERATING SYSTEM STRUCTURE
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OPERATING SYSTEM STRUCTURE

As we have examined what operating systems look like on the outside (i.e.,the programmer's interface), it is time to take a look inside. In the next sections, we will study six different

Layered Systems
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Layered Systems

A generalization of the approach of figure in previous article i.e. "OPERATING SYSTEM STRUCTURE" is to organize the operating system as a hierarchy of layers, each one constructed upon the one below it. The first system constructed in this way was the THE

Microkernels
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Microkernels

By means of the layered technique, the designers have an option where to draw the kernel-user boundary. Usually, all the layers went in the kernel, but that is not necessary. In reality, a strong case can be made for putting as little as possible in kernel mode because

Client-Server Model / Virtual Machines
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Client-Server Model / Virtual Machines

A small variation of the microkernel idea is to differentiate two classes of processes, the servers, each of which gives some service, and the clients, which use these services. This model is known as the client-server model. Sometimes the lowest layer is a microkernel, but

VM/370
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VM/370

This system, initially called CP/CMS and later renamed VM/370 (Seawright and MacKinnon, 1979), was based on an astute observation: a timesharing system provides (1)

Virtual Machines Rediscovered
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Virtual Machines Rediscovered

Though IBM has had a virtual machine product available for four decades, and a few other companies, including Sun Microsystems and Hewlett-Packard, have recently added virtual

The Java Virtual Machine  /  Exokernels
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The Java Virtual Machine / Exokernels

One more area where virtual machines are used, but in a somewhat different way, is for running Java programs. When Sun Microsystems invented the Java programming language, it also invented a virtual machine (i.e., a computer architecture)

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