Download [VERIFIED] Operating System Concepts

The tenth edition of Operating System Concepts has been revised to keep it fresh and up-to-date with contemporary examples of how operating systems function, as well as enhanced interactive elements to improve learning and the student's experience with the material. It combines instruction on concepts with real-world applications so that students can understand the practical usage of the content. End-of-chapter problems, exercises, review questions, and programming exercises help to further reinforce important concepts. New interactive self-assessment problems are provided throughout the text to help students monitor their level of understanding and progress. A Linux virtual machine (including C and Java source code and development tools) allows students to complete programming exercises that help them engage further with the material.

An Operating System(OS) is software that manages and handles the hardware and software resources of a computer system. It provides interaction between users of computers and computer hardware. An operating system is responsible for managing and controlling all the activities and sharing of computer resources. An operating system is a low-level Software that includes all the basic functions like processor management, memory management, Error detection, etc.

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Among all subjects, Operating Systems is the trickiest one, because creating even a toy operating system is a rather non-trivial task. However, at the same time an application developer (who may not have formally learned CS) must at least be aware of and hopefully should have implemented some key concepts to appreciate how an OS works, and to be a better developer.

Every OS designer must understand the concepts behind Multics. One of the most brilliant ideas is the notion of of a vast virtual memory partioned into directly readable and writable segments with full protections, and multiprocessor support to boot; with 64 bit pointers, we have enough bits to address everything on the planet directly. These ideas are from the 1960s yet timeless IMHO.

Applications such as web browsers and email tools areperforming an increasingly important role inmodern desktop computersystems. To fulfill this role, they should be incorporated as part of theoperating system. By doing so, they can provide better performanceand better integration with the rest of the system. In addition, theseimportant applications can have the same look-and-feel as the operatingsystem software.

Every self-taught programmer and computer scientist alike should know the OSI model and know it well. It helps to identify where a problem could lie and who to contact if there are problems. The scope is defined here and many issues could be filtered out here. This is because there is just too much in an operating system to simply learn it all. As a web developer I usually work in the application level when an issue ever goes out of this scope I know when i need help. Also many people simply do not care about certain components they want to create thing as quickly as possible. The OSI model is a place where someone can find their computer hot spot. _model

Fundamental operating systems concepts: processes and threads, CPU scheduling, interprocess communication and synchronization, deadlock, memory management, input/output devices, file systems, distributed systems, protection and security. Hands-on labs exploring and implementing the above listed topics. Offered fall and winter semesters. Prerequisites: CIS 241; and CIS 351 or (EGR 326 and EGR major standing).

The later trend in operating system design was to keep thecore of the operating system small and move as much as possibleinto separate programs that have the proper security privileges todo what just they need. The kernel will invoke separate processesto deal with things such as parsing a file system, interfacing withthe network, or even making a process scheduling decision. Thisapproach is called a microkernel.

If a processor is running in kernel mode, it can switch itself to user modeby setting the status register that defines its operating mode. Once it is runningin user mode, however, it cannot simply set itself to run in kernel mode sincethat would be a privilege violation. The transition from user to kernel modetakes place via traps, interrupts, and exceptions. Unfortunately, thereis not a clear consensus on the defintion of these terms. Some literature refersto traps as user-initiated instructions while other texts refer to them asunexpected violations.We will use trap as a generic term and identify three categories:

The interrupt vector table is set up by the boot loader and can later be modifiedby the operating system when it starts up. When a user program executes a trap (e.g., INTinstruction on older Intel processors; other processors and all current Intel/AMDprocessors have some form of a syscall instruction),control is transferred to the appropriate trap vectorand the processor then runs in kernel mode.

Because the interrupt table is set up by a trusted entity (the operating system) andcannot be altered by the user, the operaing system is confident that program controlgoes to only well-defined points in the operating system.

Upon entry to the trap,operating system code is run and, when theoperating system is ready to transfer control back to the user, it executes areturn from exception instruction (IRET on Intel processors). That switchesthe processor back to user mode operation and transfers control to the address on thetop of the stack.

A program often needs to read a file, write to some device, or maybeeven run another program. All these are require operating systemintervention. The interface between the operating system and userprograms is the set of system calls (open, close, read,fork, execve, etc). Making a system call uses the trapmechanism to switch to a well-defined point in the kernel, running in kernel mode.

To execute a system call usually involves storing the parameterson a specially created stack, storing the number of the system call(each function has a corresponding number), and then issuing a software interruptinstruction to switch control to the operating system operating in kernel mode.

To give the operating system a chance to to run periodically, weprogram a periodic timer interrupt when the kernel starts.On Linux/Intel systems, we set the 8254Programmable Interval Timer to generate an interrupt (IRQ 0) approximately every 10 milliseconds,although this interval can be modified based on the environment. Alternatively,the High Precision Event Timer (HPET) or the ACPI Power Management Timer (ACPI PMT)can be used to accomplish the same thing.

Device registers also tell you when data is ready (e.g., a packet has been received)or if the device is ready for more data (e.g., a packet has been transmitted). We couldhave our operating system sit in a busy loop and check these registers. Unfortunately, we willchew up tons of processor cycles just waiting for the device and not be able to use the time to do anythingelse. Instead, whenever we get a periodic clock interrupt (e.g., every 10 milliseconds), we can have theoperating system go and check those device registers. That avoids the busy loop.

In operating systems, a file is traditionally a collection ofdata with a name associated with it along with other information(length, create time, access time, owner, users who can modify thefile, etc.). In many systems, a file may also refer to adevice or even a process. Files are often organized in a hierarchicalstructure into sets of directories (sometimes referred to as folders, mostlyby users of windowing interfaces that adopt a desktop metaphor) and files. A directory is a nameof an entity that contains zero or more files or directories. Afile system is generally a collection of directories and their filesand subdirectories that occupies an entire disk or a defined sectionof a disk. It is a region of storage upon which the logical structureof file attributes and contents is laid.

All system calls under the various versions of UNIX (and indeed onjust about every other operating system) are enveloped in libraryfunctions. To the user they appear no different from any othersystem library functions. On most UNIX systems (various flavors of Linux,OS X, FreeBSD, OpenBSD, NetBSD), the functionsthat invoke the system calls are in the library called libc, whichalso includes non-system call functions (such as printf and strtok).System calls are documented in section 2 of the programming manualand can be found on-line with the man command. For information onusing the man command, run man man, which will show the manual pagefor the man command.

An operating system (OS) is the program that, after being initially loaded into the computer by a boot program, manages all of the other application programs in a computer. The application programs make use of the operating system by making requests for services through a defined application program interface (API). In addition, users can interact directly with the operating system through a user interface, such as a command-line interface (CLI) or a graphical UI (GUI).

An operating system brings powerful benefits to computer software and software development. Without an operating system, every application would need to include its own UI, as well as the comprehensive code needed to handle all low-level functionality of the underlying computer, such as disk storage, network interfaces and so on. Considering the vast array of underlying hardware available, this would vastly bloat the size of every application and make software development impractical.

As long as each application accesses the same resources and services in the same way, that system software -- the operating system -- can service almost any number of applications. This vastly reduces the amount of time and coding required to develop and debug an application, while ensuring that users can control, configure and manage the system hardware through a common and well-understood interface. e24fc04721