An operating system (OS) is system software that manages computer hardware and software resources and provides common services for computer programs.
31 Aug 2017
Layered Architecture of Operating System
This is an important architecture of operating system which is meant to overcome the disadvantages of early monolithic systems.
01 Jan 2018
Threads-Summary
Summary A thread is a flow of control within a process. A multithreaded process contains several different flows of control within the same address space. The benefits of multithreading include increased responsiveness to the user, resource sharing within the process, economy, and the ability to t...
24 Dec 2017
Critical Section problems
The critical-section problem is to design a protocol that the processes can use to cooperate. Each process must request permission to enter its critical section. The section of code implementing this request is the entry section. The critical section may be followed by an exit section. The remaining...
31 Aug 2017
Monolithic architecture - operating system
It is the oldest architecture of the operating system. We know that all the core software components of the operating system are collectively known as the kernel.
24 Aug 2017
Operating System Concepts ( Multi tasking, multi programming, multi-user, Multi-threading )
Operating system acts as an interface between the user and the hardware. It is something which relieves the user from bothering about hardware related issues. what is multitasking, Multiprogramming, Multiuser Operating System, Multithreading
27 Dec 2017
Thread Libraries
Thread Libraries A thread library provides the programmer an API for creating and managing threads. There are two primary ways of implementing a thread library. The first approach is to provide a library entirely in user space with no kernel support. All code and data structures for the library ex...
30 Dec 2017
Algorithm Evaluation
Algorithm Evaluation How do we select a CPU scheduling algorithm for a particular system? there are many scheduling algorithms, each with its own parameters. As a result, selecting an algorithm can be difficult. The first problem is defining the criteria to be used in selecting an algorithm. As we...
Computing Environments : Traditional Computing, Client-Server Computing, Peer-to-Peer Computing, Web-Based Computing
25 Dec 2017
Free Space management
Free-Space Management Since disk space is limited, we need to reuse the space from deleted files for new files, if possible. (Write-once optical disks only allow one write to any given sector, and thus such reuse is not physically possible.) To keep track of free disk space, the system maintains a...
28 Dec 2017
Log-Structured File Systems
Log-Structured File Systems Computer scientists often find that algorithms and technologies originally used in one area are equally useful in other areas. Such is the case with the database log-based recovery algorithms described in Section 6.9.2. These logging algorithms have been applied success...
24 Dec 2017
Threads overview
A thread is a basic unit of CPU utilization; it comprises a thread ID, a program counter, a register set, and a stack. It shares with other threads belonging to the same process its code section, data section, and other operating-system resources, such as open files and signals. A traditional (or h...
30 Dec 2017
RC 4000
RC 4000 The RC 4000 system, like the THE system, was notable primarily for its design concepts. It was designed for the Danish 4000 computer by Regnecentralen, particularly by Brinch-Hansen (Brinch-Hansen [1970], BrindvHansen [1973]). The objective was not to design a batch system, or a time-shari...
29 Dec 2017
Linux-Input & output
Input and Output To the user, the I/O system in Linux looks much like that in any UNIX system. That is, to the extent possible, all device drivers appear as normal files. A user can open an access channel to a device in the same way she opens any other file—devices can appear as objects within the...
There are 5 types of operating systems- Batch Operating Systems, Time Sharing Systems, Distributed Operating Systems, Network Operating Systems, Real Time Operating Systems. Operating System Types - Learning operating system concepts in simple and easy steps : A beginner's tutorial containing comple...
29 Dec 2017
Computer Security Classifications
Computer-Security Classifications The U.S. Department of Defense Trusted Computer System Evaluation Criteria specify four security classifications in systems: A, B, C, and D. This specification is widely used to determine the security of a facility and to model security solutions, so we explore it...
30 Dec 2017
Application I/o Interface
Application I/O interface In this section, we discuss structuring techniques and interfaces for the operating system that enable I/O devices to be treated in a standard, uniform way. We explain, for instance, how an application can open a file on a disk without knowing what kind of disk it is and ...
03 Jan 2018
Summary-Main Memory
Summary Memory-management algorithms for multiprogrammed operating systems range from the simple single-user system approach to paged segmentation. The most important determinant of the method used in a particular system is the hardware provided.
25 Dec 2017
Paging
Paging Paging is a memory-management scheme that permits the physical address space of a process to be noncontiguous. Paging avoids the considerable problem of fitting memory chunks of varying sizes onto the backing store; most memory-management schemes used before the introduction of paging suffe...
24 Dec 2017
Multithreading Models
Our discussion so far has treated threads in a generic sense. However, support for threads may be provided either at the user level, for user threads, or by the kernel, for kernel threads. User threads are supported above the kernel and are managed without kernel support, whereas kernel threads are ...
22 Dec 2017
Multiprocessor systems
Multiprocessing is the use of two or more central processing units (CPUs) within a single computer system. The term also refers to the ability of a system to support more than one processor or the ability to allocate tasks between them.
30 Dec 2017
what is compression in mutimdedia?
Compression Because of the size and rate requirements of multimedia systems, multimedia files are often compressed from their original form to a much smaller form. Once a file has been compressed, it takes up less space for storage and can be delivered to a client more quickly. Compression is part...
30 Dec 2017
Structure of Page table
Structure of the Page Table In this section, we explore some of the most common techniques for structuring the page table.
26 Dec 2017
Disk scheduling
Disk Scheduling One of the responsibilities of the operating system is to use the hardware efficiently. For the disk drives, meeting this responsibility entails having fast access time and large disk bandwidth. The access time has two major components. The seek time is the time for the disk arm ...
27 Dec 2017
Synchronization Hardware
Synchronization Hardware We have just described one software-based solution to the critical-section problem. In general, we can state that any solution to the critical-section problem requires a simple tool—a lock. Race conditions are prevented by requiring that critical regions be protected by lo...
01 Jan 2018
Summary of CPU Scheduling
Summary CPU scheduling is the task of selecting a waiting process from the ready queue and allocating the CPU to it. The CPU is allocated to the selected process by the dispatcher. First-come, first-served (FCFS) scheduling is the simplest scheduling algorithm, but it can cause short processes to ...
30 Dec 2017
Transforming I/O Requests to Hardware Operations
Transforming I/O Requests to Hardware Operations Earlier, we described the handshaking between a device driver and a device controller, but we did not explain how the operating system connects an application request to a set of network wires or to a specific disk sector. Let's consider the example ...
30 Dec 2017
System and Network Threats
System and Network Threats Program threats typically use a breakdown in the protection mechanisms of a system to attack programs. In contrast, system and network threats involve the abuse of services and network connections. Sometimes a system and network attack is used to launch a program attack,...
31 Aug 2017
Microkernel Architecture of operating system
The basic ideology in this architecture is to keep the kernel as small as possible. We know that kernel is the core part of the operating system and hence it should be meant for handling the most important services only.
27 Dec 2017
Petersons's Solution
we illustrate a classic software-based solution to the critical-section problem known as Peterson's solution. Because of the way modern computer architectures perform basic machine-language instructions, such as load and store, there are no guarantees that Peterson's solution will work correctly on ...
