FREE ONLINE NOTES

Main navigation

OPERATING SYSTEM

DEADLOCK | NECESSARY CONDITIONS | DEADLOCK HANDLING

By

What is Deadlock? A dead end may be a state of affairs wherever in two or additional competitory actions are every expecting the opposite to end, and therefore neither ever will. In a package, a dead end may be a state of affairs that happens once a method enters a waiting state as a result of a resource requested by it’s being controlled by another waiting method, that successively is expecting another resource. If a method is unable to vary its state indefinitely as a result of the resources requested by it are getting used by alternative waiting method, then the system is claimed to be in an exceedingly dead end.

Deadlock may be a common drawback in data processing systems, parallel computing, and distributed systems, wherever computer code and hardware locks are wont to handle shared resources and implement method synchronization.

NECESSARY CONDITIONS FOR DEADLOCK

A dead-end state of affairs will arise providing all of the subsequent conditions hold at the same time in an exceeding system:

1.Mutual Exclusion: a minimum of one resource should be one method will use the resource at any given instant of your time.

2.Hold and Wait or Resource Holding: A method is presently holding a minimum of one resource and requesting extra resources that are being controlled by alternative processes.

3.No Preemption: The package should not de-allocate resources once they need to be allocated; they have to be discharged by the holding method voluntarily.

4.Circular Wait: A method should be expecting a resource that is being controlled by another method, that successively is expecting the primary method to unharness the resource. In general, there’s a collection of waiting for processes, P = such P1 is expecting a resource control by P2, P2 is expecting a resource control by PA so on until PN is expecting a resource control by P1.

DEADLOCK HANDLING

Most current operating system cannot stop a dead end from occurring. once a dead end happens, completely different operational systems reply to them in numerous non-standard manners. Major approaches are as follows.

  1. IGNORING DEADLOCK

In this approach, it’s assumed that a dead end can ne’er occur. This can be conjointly known as the Ostrich formula. This approach was first employed by MINIX and UNIX system. This can be used once the time intervals between occurrences of deadlocks are massive and also the information loss incurred when is tolerable. It’s avoided in terribly important systems.

  1. DETECTION

Under dead end detection, deadlocks are allowed to occur. Then the state of the system is examined to notice that a dead end has occurred and after it’s corrected. Associate in Nursing formula is used that tracks resource allocation and method states, it rolls back and restarts one or additional of the processes so as to get rid of the detected dead end. detective work a dead end that has already occurred is well potential since the resources that every method has fast and/or presently requested are familiar with the resource computer hardware of the package

  1. AVOIDANCE

Deadlock is often avoided if sure data concerning processes are out there to the package before allocation of resources, like that resources a method can consume in its lifespan. For each resource request, the system sees if granting the request can mean that the system ‘bill enter an unsafe state, which means a state that would end in the dead end. The system then solely grants requests which will cause safe states. so as for the system to be ready to verify whether or not consequent state are going to be safe or unsafe, it should recognize ahead at any time:

  • resources presently out there.
  • resources presently allotted to every method.
  • resources which will be needed and discharged by these processes within the future.

SCHEDULING | ALGORITHM | SCHEDULING IN OPERATING SYSTEM

By

What is Scheduling? The Allocation of CPU time (Resources) to different jobs to be processed on the computer is called scheduling and the module of an operating system which handle this task is called scheduling.  Scheduler arranges jobs in the sequences base in the priority. In the time-sharing system, all the resources of the computer system are shared among the different user. as CPU is one of the primary computer resources so the sharing of CPU time among different user (Jobs) is term as scheduling. The Scheduler has to make a decision that which process should be given CPU time when and how much.

SCHEDULING IN OPERATING SYSTEM

SCHEDULER ALGORITHM

The following are well know scheduler algorithm.

NON-PREEMPTIVE ALGORITHM
i. FIFO

ii. LIFO.

iii. SJF

PREEMPTIVE ALGORITHM

i.  SJN

ii.  RR

a).     NON-PREEMPTIVE ALGORITHM

In this strategy when a process is assigned to CPU  will not be swapped (stopped or Blocked) before its completion.

a.i.     FIFO. (First in first out)

In this algorithm, all the incoming jobs are placed in Queue and are proceed one by one at first come first out.

a.ii    LIFO (Last in First cut)

In this Strategy incoming jobs are placed in a stack and CPU is assigned to a job which is at the top of the stack. However, it is a scheduler algorithm but it is not actually applied.

a.iii SJF (Shortest Job First)

According to this algorithm, first of all, all active process are stored according to their size and the shortest job is arranged high priority it means that a job requires less memory will be given high priority. When CPU is executing some processes, at the same time a new process arrived. All the remaining processes again arranged according to the size.

b).     PRE-EMPTIVE ALGORITHM

In this strategy when a process is assigned to CPU can be swapped (stopped) before its completion and a new process is assigned to CPU.

b.i SJN (Shortest job next)

In this strategy all the process are arranged according to their size from the smaller to larger and highest’ priority is assigned to the smaller process. Suppose a process is assigned to  Processor a new job arrived If the remaining portion of current jobless then the new. Then current process will be swapped from CPU (block state) and new process assign to processor (running State)

b.ii     RR (Round Robbins algorithm)

In this scheduling method, the process is dispatched FIFO and no priority is assigned to any job, all the active job are given a limited amount of CPU time called a time slice or quantum. If a process doesn’t complete before it CPU time expires, then this process is preemptive and CPU has given to the next waiting process. The preempted process is placed at the back of the ready list.

POPULAR OPERATING SYSTEM | TYPES OF OPERATING SYSTEM

By

What is Popular Operating System? Earlier, many operating systems were device-dependent. A type of software that runs only on a specific type computer is called device-dependent.Lets us discuss different Popular Operating System in detail;

DIFFERENT POPULAR OPERATING SYSTEM

There are generally two categories of operating systems.

1- STAND-ALONE OPERATING SYSTEMS

An operating system that works on desktop or notebook computer is called stand-alone operating system. Some example of a stand-alone operating system is DOS, Windows 95, Windows  NT Workstation, Windows Me and Windows XP Home Edition etc.

DOS

DOS stands for Disk Operating System. It was developed by Microsoft in the early 1980s for personal computers. It is a single user, single-tasking operating system,  Windows 95, 98, Me. In 1995 Microsoft introduced Windows 95 operating system, includes the feature of Graphical User Interface Windows 95 are multitasking, networking, multimedia, and many other capabilities operating a system. Microsoft introduced an enhanced Windows 98 version during 1998, Windows Me (Millennium Edition) in 2000

Windows XP

Windows XP is a product of Microsoft Corporation, It was released in 2001. XP stands for an experience. It is fastest and most reliable operating system. Three versions of Windows XP are Windows XP Home Edition, Windows XP Professional and
Windows XP Server.

MAC

Macintosh operating system is a product of Apple. It was one of the first successful GUI. It was released with Macintosh computer in 1984, The latest version of this operating system is called Mac OS X.

2- NETWORK OPERATING SYSTEM

An Operating System that supports network is called network operating system. It normally works on a server. Some example of network operating system is Windows NT Server, Windows 2000 Server, Netware, Unix, Linux, and Solaris.

NETWARE

Novell’s Netware is network operating systems. It is designed for client/server networks.

WINDOWS NT SERVER

Microsoft introduced its Windows JNT (New Technology) operating system in 1995. It is designed for client/server networks. The server in the network uses Windows NT Server. The client computer uses Windows NT Workstation.

UNIX

UNIX is multitasking. network operating system, It developed in the early 1970s at Bell laboratories, Many versions of this operating system are available, It uses command-driven interface.

LINUX

Linux is free. multitasking and nctv.ork operating system. It was developed in 199L Some version of Linux use command-line interface and other GUI.

SOLARIS

Solaris is on UNIX operating system. It was developed by Sun Microsystems. It is an operating system designed for e-commerce applications.

FUNCTION OF OPERATING SYSTEM | SYSTEM FUNCTIONS

By

What is the basic function of operating system ? There is so many various function of operating system. some of them are discussed below;

SYSTEM FUNCTIONS

An OS performs the following basic functions in the operation of a computer system.

BOOTING

Booting is a process of starting the computer. Operating system the computer to work. It checks the computer and makes it ready to work. / There are two type of booting
•           Cold Boot: When a computer is turned on by on/off button it is called cold boot.
•           Warm Boot: When a computer is restarted, it is called warm boot.

THE USER INTERFACE

As we Know that User interface is used to interact with a computer. It controls how you enter important data and various instructions and how useful information is displayed on the screen.

Three main types of user interfaces

  • Command-driven:- In a command-line user interface the user enter data and instructions by typing a keyword or pressing special keys on a keyboard.
    • Menu-Driven interface: In menu-driven interface, the user enters data and instruction by using menu. It is easier to use.
    • Graphical User Interface: the graphical user interface is a visual environment that is used by the user to communicate with a computer. It uses windows, icon„ menu and other graphical objects to issue commands.The trend towards an easy-to-use graphical user interface (GUI), which uses an icon, bars, button, boxes and images. GUI applies by the pointing devices like the electronic mouse etc.

RESOURCE MANAGEMENT

 

As we know that an operating system uses a range of resource management programs to manage the networking resources and hardware of a computer system, including its CPU, various memory, secondary storage devices, processors and input/output peripherals. For example, management programs keep track of where data and programs are stored.

MEMORY MANAGEMENT

Memory management is a process of optimizing the use of main memory. RAM is used to store data and instructions temporarily during execution. Operating system allocates Memory area to different programs. The allocated memory area is de-allocated when the program finishes.

FILE MANAGEMENT

 An operating system contains file management programs that control the creation, deletion, ånd access of files of data and program. File management also keeping track of the physical location of files on magnetic disks and other secondary storage devices.

TASK MANAGEMENT/JOB SCHEDULING

The task management programs of an operating system manage the completion of the job of end users. They provide every one assignment with a segment of a CPU’s time and butt in the CPU operations to alternate other tasks. Task management may involve multitasking capability where several computing tasks can occur at the same time. We know that latest microcomputer operating system and most minicomputer and mainframe operating systems provide a multitasking capability. With multitasking, an end user can do two or more operation (e. keyboard and printing) or use of the application (e.g. Ms-Word, Excel) concurrently, that is at the same time. A single CPU can run a number of programs at the same time. The numbers of a program that can be run concurrently depend on the amount of memory that is available and the amount of processing each job demands. That is because a microprocessor (or CPU) can become overloaded with too many jobs and provide an unacceptably slow response. Multitasking allows an end user to easily switch from one application to another.

MONITORING PERFORMANCE

It is important function of Operating system also monitors the performance of the computer. A performance monitor is a program that checks and reports information about different systems resources and devices. For example, it monitors the processor, disk, memory, and network.

ACCESSING THE WEB

Operating system provides the facility to connect to the Web. It guides the user to set up a connection between computer and Internet Service Providers. Some operating system provides the facility for Web browser and email program.

ADMINISTERING SECURITY

Another function of Operating system manages the security of computer system as well as data and program stored on it. Security is normally maintained by using User ID and passwords.

DEVICE CONTROLLING


Operating system controls all devices attached to the computer.  The hardware devices are controlled with the help of small software called device drivers.

WHAT IS OPERATING SYSTEM? TYPES OF OPERATING SYSTEM

By

What is Operating System? Operating System is a group of a program that controls all the operation of a computer system and its components. It is an integrated set Of specialized programs that are used to manage the resources and overall operation of a computer, A computer can do nothing without an operating system. It must be installed on every computer. A user interacts with the computer through Operating System. When a computer is turned on, the operating system runs and checks that all parts of the computer are functioning properly. An operating system manages all operation on a computer after loading, some popular operating system is IBM PC-DOS, MS-DOS, UNIX, XENIX, LINUX, WINDOWS-98, WINDOWS-2000, OS/2, and WINDOWS-XP.

TYPES OF OPERATING SYSTEM

An operating system is classified according to the following criteria ‘s.
1. Single User Operating Systems

2-Multi-User Operating Systems

SINGLE USER OPERATING SYSTEM

Single User Operating system allows only one user to use the system. For Micro-computer single-user operating system offer the following function.
1- Initialization of System; in which the OS must have initial loader program to initialize the system properly.

2- File Management;  An operating system contains file management programs that control the creation, deletion, and access to files of data and program.

3-Memory management. In this type of operating system, this memory management is simple, as only one application is executed at one time. If there is another application to be run the previous is removing from the memory.

4- Input-Output management: I/O management in this type of O.S is simpler as compared to Other because the one I/O device is made active at a time.

MULTI-USER OPERATING SYSTEM


Multi-User Operating system allows more than one user at a time to use the system.
The function provides by OS are:

1- Initialization. Initialization is more complex than single-user operating system because it is possible that more than one computer be initialized by a server.

2- File Management.  File Management is more complex in this case because a file maybe accesses or shared by more than one user. If a user is using currently a file and another user also trying to access this file than it is the duty of operating system to lock the file for other uses and also see Security (permissions) on file also share a file to available it Network.

3- Memory management; it available memory of server is divided among different user the rest of memory management is the same as the single OS. It also uses a technique called paging to allow your computer to run more programs than its physical memory by storing memory pages not currently in use on a mass storage device called virtual memory.

4- Input-Output Management. It is also complex because of more than one devices managed by OS.

 5-Resource Management; Resources (Printer, CD Drive, Floppy Drive etc are available to all user on a network) these devices can be share to access from other computers.

6- process Management; In a multi-user operating system, more than one application is executed at a time this capability is called multitasking.

7- processor Management. In a multi-user operating system more than one user connected to the system. Hence the processing speed must be fast to manage all user requests. For this reason, a system must have more the one processor. a multiuser system has the capability to manage all these processors.

8- Communication Management; In a multi-user operating system, one computer is connected with more than one systems. Hence it has the capability to create new user, groups and assign Passwords and permissions.

TIME-SHARED SYSTEM

It usually consists of a “dump” type terminal connected by data lines to a centralized Micro-Computer based system that controls all operations.