Where many user level threads are mapped to as single kernel thread. In such model the thread is managed by thread library in the user space which makes such model efficient. However the entire threads can be blocked if a thread makes a blocking system call. Also; with multiprocessors system; threads can access the kernel with only a single thread at a time and as such; multiple threads are unable to take advantage on multiprocessor and run in parallel on multiprocessors. With such model, developer will be able to create as many threads as required; however the true concurrency is not implemented since the kernel can schedule only one thread at a time.
Deadlocks generally take place between threads in shared memory concurrent programming as a consequence of cyclic lock acquisition. When threads wait for a resource of each other to complete task, they go to state of deadlock. There are a number of techniques proposed to avoid deadlocks mainly programming language approaches that aim for static deadlock avoidance by employing type systems to avoid deadlocks . Another method to prevent deadlock is dynamically avoid deadlocks directed by information about the order of explicit lock and unlock operations collected statically by program analysis .
Task Scheduling plays a key role in the Cloud Computing system. Scheduling of the task cannot be done on basis of single criteria. It is regulations and rules that can term as an agreement between users and providers of cloud. This agreement is nothing else simply the quality of service that the user or client requires. Providing good quality of the services to the users or clients according to the agreement it is a decisive task for the providers at the same time there is large number of tasks running at the side of provider’s. The task scheduling problem can be viewed or seen as the finding or searching an optimal mapping of set of subtasks of different tasks over the available set of the resources (e.g. processors/computer machines) hence can be achieved or attained the desired goals for tasks. Scheduling is a method or procedure by which threads, processes and data flows are given access to system resources. Scheduling is the fundamental operatingsystem function, almost all computer resources are scheduled before use. The idea of multiprogramming is relatively simple, if a job is waiting for an I/O request, then the CPU switches from that job to another job, so that it always busy in multiprogramming.
Distributed means data is stored and processed on multiple locations. Distributed OperatingSystem is a model where distributed applications are running on multiple computers linked by communications. A distributed operatingsystem is an extension of the network operatingsystem that supports higher levels of communication and integration of the machines on the network .It is a software over a collection of independent, networked, communicating, and physically separate computational nodes.  Each individual node holds a specific software subset of the global aggregate operatingsystem. Each subset is a composite of two distinct service provisioners.  The first is a ubiquitous minimal kernel, or microkernel, that directly controls that node’s hardware. Second is a higher-level collection of system management components that coordinate the node's individual and collaborative activities. These components abstract microkernel functions and support user applications.
Android operatingsystem is one of the most widely used mobile OperatingSystem these days and also enhancing its use in different areas of life. Android mobile operatingsystem is based on the Linux kernel and is developed by Google and primarily designed for smartphones and tablets . Android was created by the Open Handset Alliance, led by Google. The early feedback on developing applications for the Android platform was mixed . Issues cited include bugs, lack of documentation, inadequate Quality Assurance infrastructure, and no public issue-tracking system . A preview release of the Android SDK was released on November 12, 2007, at that time MergeLab mobile startup founder Adam MacBeth stated, "Functionality is not there, is poorly documented or just doesn't work... It's clearly not ready for prime time ." Despite this, Android-targeted applications began to appear the week after the platform was announced. The first publicly available application was the Snake game . The Android Dev Phone is a SIM-unlocked and hardware-unlocked device that is designed for advanced developers. While developers can use regular consumer devices purchased at retail to test and use their applications, some developers may choose not to use a retail device, preferring an unlocked or no-contract device.
Electric operation table is a kind of basic medical device, which plays an important role in orthopedics, orthopedics and surgery. However, the majority of operating tables distributed in more than 400,000 medical institutions nationwide are still in the situation of no monitoring, no self-diagnosis, relying on professional staff to travel for maintenance and other conditions.There are limitations such as low safety in use, high maintenance cost, and difficulty in product r&d and upgrading. At the same time, electric operating table is a relatively complex electromechanical and hydraulic coupling system, which requires high professional requirements for maintainer and is difficult to maintain. So there is usually a large lag in maintenance. Once a part of the operating table malfunctions and fails to work properly, it will not only cause great economic losses, but even influence the normal operation and endanger the lives of patients. Therefore, there is an urgent need for a system to manage and maintain the electric operating tables, which can get the real-time status of tables to monitor, tracking and diagnose the operating tables. It not only can save expenses for medical institutions, but also provide more professional, safe and effective maintenance conveniently.
8.1 Foundational services Over the years PC applications have come to expect some essential services that the OS provides (e.g., a file system). Are there similar services for the home environment? Such services should not only be broadly useful but also almost universally implementable. For instance, consider occupancy information—which rooms are currently occupied by people. It can benefit many applications (e.g., lighting control, thermostat control, and security), but depending on the devices in the home, it may be difficult to infer reliably (e.g., motion sensors can be triggered by pets; cameras are more reliable). Making occupancy an essential service requires each home to possess the necessary devices, thus increasing the cost of a basic HomeOSinstallation. (This is akin to PC or smartphone OSes specifying minimum hardware requirements.) Thus, careful consideration is needed to determine which services a system like HomeOSshould provide in all homes.
The implementation of the distributed system is very complex, as a number of issues have to be considered to achieve its final objective. The complexities should not worry the user of the distributed system from using it i.e., the complexities should be hidden from the user who uses the distributed system. This property of the distributed system is called its transparency. There are different kinds of transparencies that the distributed system has to incorporate. The following are the different transparencies encountered in the distributed systems:
Abstract: In this research paper first of all we gave a brief introduction of the operatingsystem, furthers its types is also explained with an example and its component also. In this paper we show that what kind of problem arise, when we protect our operatingsystem, how we can overcome from these problem. In this paper, we show what new requirements arise when introducing security and protection to the operatingsystem into the area of real time operatingsystem as well as distributed and many more operatingsystem.
Although many interesting research distributed operating systems have been built since the 1970s, and some systems have been in use for many years, they have not displaced traditional operating systems designed primarily to support single machines; however, some of the components originally built for distributed operating systems have become commonplace in today's systems, notably services to access files stored on remote machines. The failure of distributed operating systems to capture a large share of the marketplace may be primarily due to our lack of understanding on how to build them, or perhaps their lack of popularity stems from users not really needing many distributed services not already provided. Distributed operating systems are also an important field for study because they have helped drive general research in distributed systems.
3. One of the concerns for a secure operatingsystem is the so-called covert channels, which are the means to circumvent the security barrier enforced by the system in prevention of passing information from one security domain to a less secure domain. For example, one possible covert channel is a “timing channel”, where a Trojan horse program alternately loops and waits, in cycles of, say one minute per bit, and a program outside the perimeter that constantly tests the loading of the system may sense the information the Trojan horse intended to send. There is no general way to prevent all covert channels. It is more practical to introduce enough noise or reduce the bandwidth of such channels in the system so that they won’t be useful to an intruder.
Study of Micro C/OS-II or Vx Works or Any other popular RTOS – RTOS System Level Functions – Task Service Functions – Time Delay Functions – Memory Allocation Related Functions – Semaphore Related Functions – Mailbox Related Functions – Queue Related Functions – Case Studies of Programming with RTOS – Understanding Case Definition – Multiple Tasks and their functions – Creating a list of tasks – Functions and IPCs – Exemplary Coding Steps.
The main goal of our project is to create and implement automated quadcopter which operates on android device or smartphone. In this research, to solve above problem the full automated system of Quadcopter is design and construct and to develop an android application which will work as a joystick for a quad copter and also give live streaming of camera mounted on quad copter.