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This section discusses operating systems, what they are and the components. The overview needed is the hardware of machine, then the makeup of the kernel, user environment. ... Each hardware component is made accessible by the operating system (Hudson & Ruth, 1999) to user applications. Why is an Operating system needed to communicate between the hardware and applications? ... Thus the Operating System (OS) acts as an abstraction layer between the two. ... (Orfali, Harkey, Edwards, Orfali, & Essential client/server survival guide, 1999) InterTask Protection is similar to Semaphores, keeping tasks from interfering with each other’s resources so as to defend against an entire system shutdown, from tasks, file system, and calls to the Operating system. ... (Orfali, Harkey, Edwards, Orfali, & Essential client/server survival guide, 1999) Dynamically Linked Run-Time Extensions are a mechanism that provides services to grow at run time without recompiling the operating system. Figure 2 shows displays the typical Unix operating systems design.
Figure 2 Typical Unix Structure (Tanenbaum, 1999)
The three layers in Figure 2 are Hardware, Kernel Mode, and User Mode. These layers link the hardware to the user interface, so the computer may appear to be intelligent. ... (Loomis, 2000b) The user mode provides user access to various system resources. ... Device drivers shield the file system from the bare hardware, creating a stream to establish a two-way connection from a user process to a hardware device. ...
At the User Mode level, there are two major points of interest, the shell and user program.
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