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Layered Operating System

  Layered Operating System Layered Structure is a type of system structure in which the different services of the  operating system  are split into various layers, where each layer has a specific well-defined task to perform . It was created to improve the pre-existing structures like the Monolithic structure ( UNIX ) and the Simple structure ( MS-DOS ). Example –  The Windows NT operating system uses this layered approach as a part of it . Design Analysis : The whole Operating System is separated into several layers ( from 0 to n ) as the diagram shows. Each of the layers must have its own specific function to perform. There are some rules in the implementation of the layers as follows. The outermost layer must be the User Interface layer. The innermost layer must be the Hardware layer. A particular layer can access all the layers present below it but it cannot access the layers present above it. That is layer n-1 can access all the layers from n-2 to 0 but it canno...
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OS its Resource Manager and its Function

  Operating system as resource manager:   ·           A computer system usually has many hardware and software resources such as processor , memory, disk printer, I/O devices etc. ·           The task of resources management becomes essential in multi-user operating system where different user compute for the same resource.   Operating system manages resources in two ways : 1.         Time multiplexing : it defines the sharing of resources on the basis of fixed time slices. For example, the operating system allocate the resources, such as CPUto program A for fixed time slice. 2.         Space timing:  it defines the concurrent sharing of resources among different programs.for example, sharing of hard disk and main memory is space multiplexing.     FUNCTION OF OPERATING SYSTEM     The primar...
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Monolithic Architecture

  Monolithic Architecture Monolith means composed all in one piece. The  Monolithic  application describes a single-tiered  software  application in which different components combined into a single program from a single platform. Components can be: Authorization — responsible for authorizing a user Presentation — responsible for handling HTTP requests and responding with either HTML or JSON/XML (for web services APIs). Business logic — the application’s business logic. Database layer — data access objects responsible for accessing the database. Application integration — integration with other services (e.g. via messaging or REST API). Or integration with any other Data sources. Notification module — responsible for sending email notifications whenever needed. Example for Monolithic Approach Consider an example of Ecommerce application, that authorizes customer, takes an order, check products inventory, authorize payment and ships ordered products. This applicat...
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Suspend a process

  Suspend a process A process is an active program. It can also be said as a program that is under execution. It is more than the program code as it includes the program counter, process stack, registers, program code etc. Compared to this, the program code is only the text section. A process passes through different states as it executes. These states may be different in different operating systems. However, the common process states are explained below with the help of a diagram − New This is the state when the process has just been created. It is the initial state in the process life cycle. Ready In the ready state, the process is waiting to be assigned the processor by the short term scheduler, so it can run. This state is immediately after the new state for the process. Ready Suspended The processes in ready suspended state are in secondary memory. They were initially in the ready state in main memory but lack of memory forced them to be suspended and gets placed in the second...
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Scheduler

  Scheduler   Scheduling Objectives Here, are important objectives of Process scheduling Maximize the number of interactive users within acceptable response times. Achieve a balance between response and utilization. Avoid indefinite postponement and enforce priorities. It also should give reference to the processes holding the key resources  Process Scheduling handles the selection of a process for the processor on the basis of a scheduling algorithm and also the removal of a process from the processor. It is an important part of multiprogramming in operating system. Process scheduling involves short-term scheduling, medium-term scheduling and long-term scheduling. Details about these are given as follows − Long-Term Scheduling Long-term scheduling involves selecting the processes from the storage pool in the secondary memory and loading them into the ready queue in the main memory for execution. This is handled by the long-term scheduler or job scheduler. The long-term s...
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