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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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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. ...

Time Sharing System and its Requirements

Time sharing system · Time sharing refers to the allocation of computer resources in a time dependent fashion to several program simultaneously · A time sharing system has many user terminals that are connected to same computer simultaneously. Using these terminal, different users can work on a system at the same time · Thus, it uses multi programming with a special CPU scheduling among all the last one, and then again beginning from the first one · In time sharing system, the CPU time is divided among all the users on schedule basis. · It release the CPU under any of the following three conditions: 1. When the allotted time slice expires. 2. ...

Distributed system

Distributed system · A distributed system is a collection of processor located in geographical dispersal physical location. · In this system, the workhold is distributed or divided between two or more computers that are linked together by communication network . that is the different processors communicate using communication links, such as telephone lines and buses3 · The various processors do not share memory, clock ,or peripheral devices instead each processors has its local memory. · The purpose of distributed system is to provide an efficient and convenient environment for sharing of resources. · Some example of distributed operating system are amoeba, angle, chorus, much, alpha kernel. · ...

Multitasking System

Multitasking system · Technically , multitasking is same as multi programming · In a multitasking operating system, s single user can execute multiple programs at the same time · We can also say, multitasking is the system capability to work on more than one job or process at the same time. · It means that whenever a job needs to perform I/O operation, the cpu can be used for execting some other job diagram of multi tasking · There are two type of multitasking : 1. ...

Real-time system

R eal-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. R eal-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 ...