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Real Time Operating System

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Real Time Operating System REAL TIME OPERATING SYSTEM ABSTRACT A real-time operating system (RTOS) is an • Media playback operating system (OS) intended for real-time • Scientific visualization applications . Such operating systems serve • Games application requests nearly real-time. A real- • Interactive applications time operating system offers programmers more Distributed real-time systems are those which have control over process priorities. Real time means multiple resources with non-negligible latency among immediate response from the computer. Thus them. Examples include the multiple processors in a a system in which a transaction that we access car, or media being streamed and update a file quickly enough to affect original decision making is called a real time The term real-time derives from its use in early operating system. A real time operating system simulation. While current usage implies that a has well defined time constraints. computation that is 'fast enough' is real-time, originally it referred to a simulation that proceeded at a rate that matched that of the real process it was INTRODUCTION simulating. Analog computer especially, were often capable of simulating much faster than real-time, a An operating system (OS) is a software , consisting situation that could be just as dangerous as a slow of programs and data that runs on computers and simulation if it were not also recognized and manages the computer hardware and provides accounted for. common services for efficient execution of various application software.A good operating system (OS) Hard and soft real-time systems provides a solid interface to the hardware and allows A system is said to be ''real-time'' if the total the application to be managed in the most efficient correctness of an operation depends not only upon its manner possible. logical correctness, but also upon the time in which it is performed. The classical conception is that in a Real-time operating systems are software/hardware '''hard real-time''' or '''immediate real-time system''', systems in which timing the completion of an operation after its deadline is constraints must be met for correctness. “Real-time” considered useless - ultimately, this may cause a does not mean “really fast”, but rather “get this done critical failure of the complete system. A '''soft real- by the deadline or else you have failed.” Such hard time system''' on the other hand will tolerate such real-time systems are ubquitous and vital in a range lateness, and may respond with decreased service of places from everyday life to quality (e.g., omitting frames while displaying a estoteria: video). • The ignition, fuel injection, and timing of most car engines is handled by a real-time system. Hard real-time systems are used when it is imperative • The antilock brake system in most cars is a real-time that an event is reacted to within a strict deadline. system. Such strong guarantees are required of systems for . which not reacting in a certain interval of time would • The software of the Mars Rovers is architected cause great loss in some manner, especially damaging around VxWorks, a commercial real-time operating the surroundings physically or threatening human system.Most hard real-time systems are embedded lives (although the strict definition is simply that systems, meaning the software is missing the deadline constitutes failure of the system). codesigned with the hardware, under often severe cost For example, a [automobile|car] [engine] control constraints, to accomplish a specific task. The user system is a hard real-time system because a delayed doesn't see the system as a general purpose computer. signal may cause engine failure or damage. Other examples of hard real-time embedded systems include Soft real-time systems are penalized by how much medical systems such as heart[artificial pacemaker| they miss the desired deadlines and by the variance of pacemaker] and industrial process controllers. Hard their latency. Such systems show up in many familiar real-time systems are typically found interacting at a places in general purpose computers, or should: low level with physical hardware, in [[embedded system]]s. Early video game systems such as the Windows operating system. Components installed on [[Atari 2600]] and [[Cinematronics]] vector graphics Windows include a Windows kernel driver and a had hard real-time requirements because of the nature number of Windows services. The driver manages of the graphics and timing hardware. memory for the kernel and real-time applications to run in, and manages the communications Soft real-time systems are typically used where there interface between the two systems. is some issue of concurrent access and the need to keep a number of connected systems up to date with changing situations; for example software that A Windows service loads the real-time kernel into the maintains and updates the flight plans for commercial allocated memory and then causes a context switch [[airline]]rs. The flight plans must be kept reasonably from Windows to the INtime kernel. A low-priority current but can operate to a latency of seconds. thread is created whose function is to switch the machine context back to the Windows system. Because this thread will be preempted by all other real-time threads, as far as the real-time kernel is RECENT WORK IN FIELD concerned, the Windows system is the real-time system's idle task. The 31st IEEE Real-Time Systems Symposium (RTSS) in San Diego, California, will follow the When in the INtime context, any real-time interrupts format of recent RTSSs, with multiple tracks. RTSS is are handled directly, and all other interrupts are the premier conference in the area of real-time masked at the interrupt controller. When the context computing, presenting innovations in the field with returns to Windows, these interrupts are unmasked to respect to theory and practice. allow normal processing by Windows. When a real- time interrupt occurs in the Windows context, the RTSS provides a forum for the presentation of high- Windows IDT is patched so as to cause a context quality, original research covering all aspects of real- switch to the INtime context so the interrupts may be time systems design, analysis, implementation, handled. evaluation, and experiences. RTSS’10 continues the trend of making RTSS an expansive and inclusive The system timer is usually shared between Windows symposium, looking to embrace new and emerging and INtime. The hardware timer is reprogrammed to areas of real-time systems research. interrupt at a higher rate than Windows requires, and the Windows handler is only invoked as required. RTSS’10 welcomes the submission of mature papers Typically, the INtime kernel takes timer interrupts at a in several areas of real-time computing, including but much higher rate (a period as low as 100µs is not limited to scheduling; databases; observability; possible) to allow for finer granularity timing services. composability; security for real-time systems; tools Optimization of the timer handling avoids and reduction to practice; control and adaptive RT unnecessary context switches between Windows and systems theory; testing and debugging; modeling; INtime. formal methods; communications (wireless, wireline, and sensor networks); power, thermal, and energy Certain hardware abstraction layer (HAL) entry points management; embedded systems; sensor and are intercepted and monitored in order to prevent the implantable devices; robustness; fault tolerance and Windows kernel from performing unwanted actions robustness; intelligent behavior; time-sensitive such as masking a real-time interrupt, or changing the robotics; emergency/disaster management; embedded hardware system timer frequency. The HAL file is not real-time systems and infrastructures; QoS support; modified or replaced by the software. real-time systems middleware, and cyber-physical systems. SCOPE FOR THE RESEARCH WORK RELATED DATA INtime is implemented as a real-time operating system which shares the hardware platform with the The INtime kernel provides operating system services links are supported through Serial Line Internet for the real-time virtual machine. It provides the real- Protocol (SLIP). time services expected of such a kernel, consisting of a priority-based preemptive scheduler with priority- USB support is provided as a development kit for based interrupt handling. Thread priorities range from developing USB client software. Standard drivers are 0 (highest priority) to 255 (lowest priority) and provided for Universal Host Controller (UHCI), Open threads below a configurable priority threshold can Host Controller (OHCI), and Enhanced Host time-slice with threads of equal priority. The kernel Controller (EHCI) interfaces. scheduler has been optimized for maximum interrupt performance. Other drivers are provided for a range of standard and industrial interface. The resulting platform exhibits good performance, and above all its behavior is predictable. Win32 API Win32 API lacks some useful features for real-time programming, INtime provides a Win32 API for ease of transporting code from Windows applications. This implementation is a rich subset of the Windows CE Win32 implementation, including a useful subset of Win32 objects, WaitForMultipleObjects, and with extensions to manage interrupts and Peripheral Component Interconnect (PCI) bus configuration Windows APIs PRESENTATION WORK APIs are provided for Windows applications to allow them to share objects created on the real-time kernel. queue
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