Kernel Mode

Introduction To Operating System
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Introduction To Operating System

A present computer comprises one or more processors, some main memory, disks, printers, a keyboard, a mouse, a display, network interfaces, and several other input/output devices. All in all, a complex system. If every application programmer had to understand how all

WHAT IS AN OPERATING SYSTEM?
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WHAT IS AN OPERATING SYSTEM?

It is difficult to understand exactly what an operating system is other than saying it is the software that runs in kernel mode and even that is not always true. Part of the problem is

Processors
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Processors

The "brain" of the computer is the CPU. It brings instructions from memory and carries out them. The fundamental cycle of every CPU is to bring the first instruction from memory, interpret it to decide its type and operands, execute it, and then bring, decode, and carry out

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

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

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)

Hybrid Implementations / Scheduler Activations
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Hybrid Implementations / Scheduler Activations

Different ways have been considered to try to unite the benefits of user-level threads with kernel-level threads. One way is use kernel-level threads and then multiplex user-level threads onto some or all of the kernel threads, as shown in the following figure. When this approach is

Interrupts Revisited
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Interrupts Revisited

We briefly introduced interrupts in "Handheld Computer Operating Systems" but there is more to be said. In a typical personal computer system, the interrupt structure is as illustrated in Figure 1. At the hardware level, interrupts work as follows. When an I/O device has finished

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