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.

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

Advantages of multi user operating system

· It helps in the sharing of data and information among different users.

· It also helps in the sharing of hardware resources such as printer and modems.

Disadvantages of multi-user

· It requires expensive hardware to setup a mainframe computer.

· When multiple users log on or work on same system it reduces the overall performance of system.

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Defination of OS(operating system) and its concepts

What do you mean by operating system? Definition : An operating system is a program that act as an interface between the user of a computer and the Computer hardware. Operating system is a first program that gets loaded into the memory through a process called booting. Concepts of operating system : · The purpose of operating system is to provide an environment in which a user can execute program in a convenient and efficient manner. · Operating system is an integrated set of program that manages the various hardware resources such as processor, memory, I/O Devices , communication devices and overall operation of a computer system. · Operating systems also acts as a platform on which various applications programs such as word processor and excel are executed. · The most common operating system are the window family of operating system (windows 98, window

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. System processes 2. Interactive processes 3. End-user processes 4. Interactive processes · In this example, each queue has absolute priority absolute over low priority queues

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 )- send a message to process A Receive(A, message )-receive a message from process B Indirect communication · In indirect communication , no direct communication link exists between two processes. · In this , messages are sent to and received from mailbox. · A mailbox is a specialized repository where message can be placed by processes and from

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. Cooperative multitaskin g 2. Preemptive multitasking · Co operative multitasking in cooperative multitasking , program can aquire the cpu for the required amount of time a program canshare CPU with any other program that is executing simultaneously, if it does not currently require the CPU. · Preemptive multitasking . In preemptive multitasking the operating system allocat

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 · Cooperating processes can communicate in a shred memory environment . · The various reasons for using cooperating processes are: 1. Information sharing : when several users want to acce

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