Real-time system

Real-time system

· In a real time operating system, a job is to be completed within the rigid time constraints otherwise job loses its meaning.

· A real time system function correctly only if it returns the correct result within its time constraints

· Thus, in a real-time system, the correctness of the computation not only depends upon the logical correctness of the computation but also upon the time at which the result is produced.

Real-time system

In a real time system various functions like process scheduling, memory management, I/O management and file management are performed as follows :

1. Process scheduling . the real time system uses priority based pre-emptive scheduling. each process is assigned a certain level of priority and the process with the highest priority is allocated the processor among those which are in the ready state.

2. Memory management. In real time system, the processes remain in primary memory for most of the time in order to provide quick response.

3. I/O device management . time critical device management is main requirement of real time system . it also uses feature like interrupt management and I/O buffering.

4. File management. In real time system, file management does not aim at efficient utilisation of secondary storage rather main objective is to provide fast access.

single user operating system

2. Multi user operating system

3. Batch processing operating system

4. Multi programming operating system

5. Multi tasking operating system

6. Multiprocessing operating system

7. Time sharing operating system

8. Real time system

Real-time operating system are categorised into:

1. Hard real-time systems

2. Soft real-time systems

1. Hard real time systems complete the critical tasks within the definite interval of constraints. If the critical task is not completed within the time constraints then the hard real time system fails.

Thus, a hard real time system has to complete all the processes within definite deeding and a single miss leads to critical failure

2. Soft real time system are less restrictive in a nature and are not affected the lapse of time interval and do not cause any critical failure.

Soft real time system are used in the area of multimedia, virtual reality

Comparison between soft real time and hard real time system

Comments

Exokernel architecture

Exokernel architecture Most of us know what kernels are and how do they work to make programmers’ lives easier. But, how many of us know what exokernels are? I hope you will be able to get a brief introduction on this terminology through this blog. Let’s start with a brief introduction on kernel. What is a kernel? A kernel is the foundational layer of an operating system that functions at a basic level, communicating with hardware and managing resources, such as CPU and the memory. It works as an interface between the user application and the hardware. There are two main types of kernel 1. Micro kernel 2. Monolithic Kernel 1. Monolithic architecture 2. Layerd archtecture . 3. Virtual machine architecture 4. Exokernel architecture 5. Client server architecture 6. Micro kernel architecture Now let’s head into our main focus. What is an Exokern...

Shortest Job First Scheduling (SJF)

Shortest Job First Scheduling (SJF) · SJF ia also known as shortest-job-next(SJN) algorithm and is faster than FCFS. · In SJF, the process with the least estimated execution time is selected from the ready queue for execution. · For this, SJF algorithm associates with each process, the length of its next CPU burst. When the CPU is available, it is assigned to the process that has the smallest next CPU burst. · If tow processes have the same length of next CPU burst ,FCFS scheduling algorithm is used to break the tie. · SJF algorithm can be preemptive or non-preemptive. Non-preeptive SJF · In non-preemptive SJF, scheduling, CPU is always assigned to the ...

Thread

Thread What is Thread? A thread is a flow of execution through the process code, with its own program counter that keeps track of which instruction to execute next, system registers which hold its current working variables, and a stack which contains the execution history. A thread shares with its peer threads few information like code segment, data segment and open files. When one thread alters a code segment memory item, all other threads see that. A thread is also called a lightweight process . Threads provide a way to improve application performance through parallelism. Threads represent a software approach to improving performance of operating system by reducing the overhead thread is equivalent to a classical process. Each thread belongs to exactly one process and no thread can exist outside a process. Each thread represents a separate flow of control. Threads have been successfully used in implementing network servers and web server. They also provide a suitable foundation ...

Multi user Operating System

Multi user operating system · In a multi-user operating system, multiple number of user can access different resources of a computer at a same time. · The access is provided using a network that consists of various personal computer attached to a mainframe computer system. diagram of multi -user operating system · The various personal computer can send and receive information to mainframe computer system. · The example of multi-user OS are UNIX, windows 2000,novell netware. sing...

Priority scheduling

Priority scheduling In priority scheduling , a priority is associated with all processes. Process are executed in sequence according to their priority. The CPU time is allocated to the process with highest priority. If the priority of two or more processes are equal than the process that has been inserted first into the ready queue is selected for execution. In other words, FCFS scheduling is performed when wo or more processes have same priority. The priorities are implemented as affixed range of numbers such as 0to 7 or 0 to 4,095. In other system, a low number indicates a high priority . in that case,a process with priority 0 is executed first. Priorities can be defined in two ways : internal or externall. ...

Easytolearn

Search This Blog