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Comparison between real time and time sharing operating system

Protection and security

• Protection refers to a mechanism for controlling the access of program s processes, or users to the resources defined by computer system.

• The concept of protection came with the advent of multiprogramming where several processes compete for the use of CPU.

• the purpose was to confine each users program to its assigned areaof memory so that the programs cannot interface and harm each other.

• Protection in main memory is particularly important because of address translation. The purpose of protection is to allow concurrently running process to share the common physical address space.

• Protection also ensure that only process that have gained proper authorization from the operating system can operate on memory segment , the CPU, files and other resources.

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Multilevel Feedback queue scheduling (MFQ)

Multilevel Feedback queue scheduling (MFQ) · Multilevel feedback queue scheduling is an enhancement of multi-levelqueue scheduling. In this scheme, processes can move between the different queue · The various processes are separates in different queue on the basis of their CPU Burst Char characteristics · If a process consumes a lot of CPU time , it is placed into a lower priority queue. Thus I/O bound and interactive process are placed in the higher priority queue and CPU bound pricesses are in lower priority · If a processes waits too long in a lower priority queue it is moved higher priority queue. Such an aging prevents starvation. · The top priority queue is given smallest CPU time Quantum · ...

ENTERPROCESS COMMUNICATION AND SYNCHRONIZATION

ENTERPROCESS COMMUNICATION AND SYNCHRONIZATION · In multi programming environment multiple process co-exit . a single program may be broken into number of processes. · The process are classified into two categories : independent processes and cooperating processes. · An independent process is a standalone process that does not share any data with any other process. It cannot affect or be affected by the other processes executing in the system. In other words, the modification made to an independent process does not affect the functioning of other process. · A cooperating processes is a process that shares data with other processes in a system it can affect or be affectedly the other processes executing in the system · ...

Round Robin

Round Robin · Round robin Scheduling is similar to FCFS but preemption is addede to switch between processes. · In RR scheduling, processes are dispatched in FIFO but given a small amount of CPU time. This small amount of CPU time this small amount of time is known as time quantum or time slice. A time quantum is generally from 10 to 100 milliseconds · If a process does not complete before its time slice expires, the CPU is time slice and is given to the next waiting process in ready queue. · The preempted process in then places at the tail of the ready queue. · If a process is completed before its time slice expires, the process itself release the CPU. The scheduler then proceeds to the next process in ready queue. ...

Multi Level Queue Scheduling (MLQ)

Multi Level Queue Scheduling (MLQ) · Multilevel queue scheduling classifies the processes according to their types for example, a multilevel queue scheduling algorithm makes a common. · In this scheduling ready queue is divided into various queue that are called sub queues. A subqueue is a distinct operational queue · The process are permanently assigned to subqueues, generally based on some property of the process such as memory size,priority or process type · Each subqueue has its process sucheduling algorithm. For example interactive process at the foreground may use round robin scheduling while batch jobs at the background may use the FCFS method · For example, consider a system with four different queues 1. ...

Direct Communicationand Indirect communication

Direct Communication · Direct communication establishes a link between two processes. A communication link is a unidirectional path along which information flows. · two processes use single communication link to share information. · In this metod, there cannot be more that one link between two processes direct communication · Send and receive function used in direct communication are given below : · Send(process name , message ,(receive(process name , message) Send(A, message...