System Calls

The Shell
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The Shell

The operating system is the code that carries out the system calls. Editors, compilers, assemblers, linkers, and command interpreters certainly are not part of the operating system, even though they

SYSTEM CALLS
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SYSTEM CALLS

Operating systems have two major jobs: providing abstractions to user programs and managing the computer's resources. Mostly, the interaction between user programs and the

System Calls for Process Management
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System Calls for Process Management

The first group of calls in figure (a). deals with process management. Fork is a good place to start the discussion. Fork is the only way to create a new process in POSIX. It produces an exact duplicate of the

System Calls for File Management
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System Calls for File Management

Many system calls relate to the file system. In this section we will look at calls that operate on individual files; in the next one we will study those that involve directories or the file system as a whole.

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

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

Process Creation
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Process Creation

Operating systems require some way to make processes. In very simple systems, or in systems designed for running only a single application (e.g., the controller in a microwave oven), it may be possible to have all the processes that will ever be needed be present when

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