Monday, 7 March 2016

External structure of an operating system

Kernel and utilities

The operating system includes a number of routines (subroutines). the most important are the core or kernel. It is loaded into memory live at system initialization and contains many procedures needed to ensure system operation. Other routines, less critical, are called utilities.
The kernel of an operating system consists of four main parts: the manager tasks (or processes), the memory manager, and file manager IO Device Manager. It also has two auxiliary parts: charger operating system and shell.


Characteristics of an Operating System

Multitasking Systems

Most modern operating systems allow running multiple tasks both: a computer can, while executing a user program, read the data from a disk or display results on a terminal or printer. We talk about multi-taskingoperating system or multi-programmed in this case.


The three main functions of an operating system

An operating system basically performs three independent tasks: it allows load after each other programs, it emulates a virtual machine and manages resources. Specify each task.


What is OS/2?

OS/2 stands for operating system/2, an operating system that was developed by Microsoft C01poration and IBM,and now being improved and marketed exclusively by IBM. OS/2 runs on 286-, 386-, and 486-based IBM PCs andcompatibles. OS/2 has many of the same commands as DOS, can read DOS disks, but it is more sophisticated than DOS. In particular, OS/2 is a multi-tasking, multi-threaded operating system. Multi-tasking means it can run more than one application at a time; multi-threaded means that a single program can perform multiple separate tasks at the same time.


What is MS-DOS?

MS-DOS (pronounced "em ess doss") stands for Microsoft disk operating system, the most widely-used operating system for IBM PC and compatible computers (an operating system is the master control software program that runs the computer itself). This means that MS-DOS is the most widely used computer operating system, period, since there are something like 80 to 100 million PCs in the world, and most of them use MS-DOS. There are at least two other versions of DOS that are compatible with MS-DOS (meaning they work the same way and run the same programs). So please see the definition for DOS for the whole story.


What is File System?

Computers are asked to store massive amounts of information on storage media such as floppy disks and hard disks. Long ago, the computer just saved all the files on the disk, and if you weren't careful, you could end up with a list of files so long you could strain your wrist just trying to scroll through them all! It was kind of like putting all the papers into your filing cabinet without folders.


What is cooperative multitasking?

Cooperative multitasking A MULTITASKING scheme under which each concurrently running program must at intervals voluntarily relinquish control of the CPU to the next program. Such programs must be specially written to suspend themselves in some non critical section and so, conversely, programs that are not so written cannot be multitasked. This contrasts with PRE-EMPTIVE MULTITASKING in which the OPERATING SYSTEM itself periodically suspends each task, so that any program may be multitasked. Apple's MACOS is a cooperative multitasking system, whereas UNIX and WINDOWS are preemptive.



If you have a PC you probably have a file named CONFIG.SYS on the disk you use to start, or boot, the computerA file that is automatically read at start up by the MS-DOS operating system used to load the DEVICE DRIVERS required by the various peripherals connected to the computer, and to set the correct configuration parameters for them. This file contains a variety of instructions used to customize the way your system works. Each time you start or restart the machine, the CONFIG.SYS file is read by the operating system (DOS or OS/2), which configures itself according to the instructions in the file. In DOS the typical CONFIG.SYS file starts with commands that tell the operating system how many files can be in use at anyone time, and how many buffers to create, like this:


What is command line interface?

In operating systems like DOS and Unix, and in many text-based or character mode programs, you control what's happening by typing commands on a command line. The command line is simply the line on the screen where you type your commands. The only way to control an operating system or a program that uses a command line interface like this is by typing commands-you don't get menus, dialog boxes, or buttons.


What is command interpreter or command processor?

command interpreter, or command processor, is that crucial part of the operating system software that interprets, or processes, the commands you give, and then carries them out for you. In DOS, the command processor is usually COMMAND. COM, although DOS lets you substitute another command processor if you want. This sounds pretty technical and scary, but it really isn't difficult.


What is cipher text?

Cipher textis information that has been changed into secret code for security reasons. A scheme for encoding messages to prevent them being read by unauthorized persons. It may have been enciphered,encrypted,or encoded, but it all means the same thing: it doesn't look like English so no one can use the information unless they have thepasswordto decode it.


What is BSD UNIX?

BSD UNIX (Berkeley System Distribution) A family of versions of the UNIX operating system developed at the University of California at Berkeley in the early 1980s. BSD Unix version 4.0 was released in 1980 for DEC's VAX and PDP-ll computers. BSD Unix introduced many technical enhancements that have now been universally adopted, such as paged VIRTUAL MEMORY and built-in TCP/IP networking. It formed the basis for several commercial UNIX versions, including Sun's (prior to Solaris 2) and Hewlett Packard's ULTRIX.


What is batch processing?

Batch processing: The grouping together of several processing jobs to be executed one after another by acomputer, without any user interaction. This is achieved by placing a list of the commands to start the required jobs into a BATCH FILE that can be executed as if it were a single program: hence batch processing is most often used in operating systems that have a COMMAND LINE user interface. Indeed, batch processing was the normal mode of working in the early days of mainframe computers, but modern personal computer applications typically require frequent user interaction, making them unsuitable for batch execution.


What is Parallel Processing Systems?

Parallel Processing Systems are designed to speed up the execution of programs by dividing the program into multiple fragments and processing these fragments simultaneously. Such systems are multiprocessor systems also known as tightly coupled systems. Parallel systems deal with the simultaneous use of multiple computer resources that can include a single computer with multiple processors, a number of computers connected by a network to form a parallel processing cluster or a combination of both.


Definition Multiprocessor Operating System

Multiprocessor Operating System refers to the use of two or more central processing units (CPU) within a single computer system. These multiple CPUs are in a close communication sharing the computer bus, memoryand other peripheral devices. These systems are referred as tightly coupled systems.


Definition of Real Time Operating Systems

Real time Operating Systems are very fast and quick respondent systems. These systems are used in an environment where a large number of events (generally external) must be accepted and processed in a short time. Real time processing requires quick transaction and characterized by supplying immediate response. For example, a measurement from a petroleum refinery indicating that temperature is getting too high and might demand for immediate attention to avoid an explosion.


Definition of Network Operating System

Network Operating System is an operating system that includes special functions for connecting computersand devices into a local-area network (LAN) or Inter-network. Some popular network operating systems are Novell Netware, Windows NT/2000, Linux, Sun Solaris, UNIX, and IBM OS/2.


Definition of Distributed Operating System

Distributed Operating System is a model where distributed applications are running on multiple computers linked by communications. A distributed operating system is an extension of the network operating system that supports higher levels of communication and integration of the machines on the network.


Definition of Multitasking Operating System

Multitasking is a logical extension of multiprogramming system that supports multiple programs to run concurrently. In multitasking more than one task are executed at the same time. In this technique the multiple tasks, also known as processes, share common processing resources such as a CPU. In the case of a computer with single CPU, only one job can be processed at a time. Multitasking solves the problem by scheduling and deciding which task should be the running task and when a waiting task should get turn. This attempt is done with the help of interrupt (a signal) which is attended by CPU by keeping the current activity aside, saves its present status in buffer and returns to another important job whatever task it was doing earlier. The act of re-assigning a CPU from one task to another one is known as context switch.


Time Sharing Operating System

time sharing system allows many users to share the computer resources simultaneously. In other words, time sharing refers to the allocation of computer resources in time slots to several programs simultaneously. For example a mainframe computer that has many users logged on to it. Each user uses the resources of the mainframe -i.e. memoryCPU etc. The users feel that they are exclusive user of the CPU, even though this is not possible with one CPU i.e. shared among different users.


Definition of Multiprogramming Operating System

To overcome the problem of underutilization of CPU and main memory, the multiprogramming was introduced. The multiprogramming is interleaved execution of multiple jobs by the same computer.


What is Batch Processing Operating System?

To avoid the problems of early systems the batch processing systems were introduced. The problem of early systems was more setup time. So the problem of more set up time was reduced by processing the jobs in batches, known as batch processing system. In this approach similar jobs were submitted to the CPU for processing and were run together.


Type of Operating System Services

Following are the services provided by an operating system for the convenience of users:

  1. Program Execution
The purpose of computer system is to allow the users to execute programs in an efficient manner. The operating system provides an environment where the user can conveniently run these programs. The user does not have to worry about the memory allocation or de-allocation or any other thing because these things are taken care of by the operating system.


Type of Computer System Components

computer system can be divided into five components; the hardware, the operating system, the utilities, the application programs and the end users. Following diagram shows the actual position of an operating system among these components.


What is Spooling

Spooling - simultaneous peripheral operations on-line, spooling refers to as a process that putting jobs in a buffer or say spool, or temporary storage area, a special area in memory or on a disk where a device can access them when it is ready. Spooling is useful because devices access data at different rates.


Difference between Application Software and System Software

Operating System is the System Software that makes the Computer work. We can say that an Operating System (OS) is Software that acts as an interface between you and the hardware. It not only contains drivers used to speak the hardware's language, but also offers you a very specific graphical user interface (GUI) to control the computer.


What is the Real Time System ? Difference between Hard and Soft Real-Time Systems.

Real Time System : There is also a Operating System which is known as Real Time Processing System. In this Response Time is already fixed. Means time to Display the Results after Possessing has fixed by the Processor or CPU.


What is Marshalling

Marshalling is the process of gathering data and transforming it into a standard format before it is transmitted over a network so that the data can transcend network boundaries.

Explain Memory Partitioning, Paging, Segmentation.

Memory partitioning is the way to distribute the Kernel and User Space Area in Memory.

Paging is actually a minimum memory, which can be swap in and swap out from Memory. In modern Server operating systems, we can use Multiple Page Size Support. That actually helps to tune OS performance, depending on type of applications.


What is Demand Paging

The Demand Paging is also same with the Simple Paging. But the Main Difference is that in the Demand Paging Swapping is used. Means all the Pages will be in and out from the Memory when they are required. When we specify a Process for the Execution then the Processes is stored firstly on the Secondary Memory which is also known as the Hard Disk.

What is Virtual Memory

Virtual Memory:   As we know that a Computer is designed for Performing the Multiple Tasks at a Time and for this Some Memory is also used by the Computer for executing the instructions those are given by the user. But when there is a Situation when the Memory (RAM) which is required by the user is high from the Available Memory. So at that situation we will use the Concept of Virtual Memory.


Explain Memory Partition or non Contiguous Allocation

As we know that operating system is that which executes the system and the operating system is the software which is responsible for running all the user programs so that generally memory is divided in to the two parts, first part is used by the operating system and the second part is used by the user programs and there may be some situations that the memory size of the operating system may be higher from the user memory and also vice versa.


What Variable Partitioned or Dynamic Memory Allocation

As we know that there are many problems arise in the continues memory allocation so that we uses the concept of the dynamic memory allocation. In the dynamic memory allocation memory is divided into the various partitions at the run time.


What is Swapping

For improving the performance of the system we use the concept of swapping. In the swapping the processes those are on waiting state and those are on suspend or temporary suspend will be stored from out side the memory locations so that the speed of process will be high.


What is Memory management

As we know that memory is that which stores the programs and these programs are used by the CPU for processing.  And there are two types of memories first is the logical memory and second is the physical memory. the memory which is temporary such as ram is also known as the temporary memory and the memory which is permanent such as hard disk is also known as the physical memory of system.


Explain Process Control block (PCB)

Process Control block is used for storing the collection of information about the Processes and this is also called as the Data Structure which Stores the information about the process. The information of the Process is used by the CPU at the Run time. The various information which is Stored into the PCB as followings:


Explain Arrangement of Files or Concept of directory Structure

Files are used for storing the Information of the user. Generally for arranging all the Files directories or Folders are used. A Folder or Directory is also called as the Container of the Files in which many Sub directors and Files are Stored. So that Files System Specifies the Arrangement of the Files in the System. There are following Directory Structures Available for organizing all the Files.

Explain File System Architecture and its Types

File System: Files are used for storing the Information of the user; But Files are organized into the System by using a Specific Manner. Generally for arranging all the Files, directories or Folders are used.

Explain File Sharing and Locking

The Concept of File Sharing and Locking is used in the Multi-users Environment, or in which there are many users those are Requesting for a Single File, to Perform Some Operations.

What is Files & Types of Files? Types of File Operations.

Files: As we know that Computers are used for storing the information for a Permanent Time or the Files are used for storing the Data of the users for a Long time Period. And the files can contains any type of information means they can Store the text, any Images or Pictures or any data in any Format. So that there must be Some Mechanism those are used for Storing the information, Accessing the information and also Performing Some Operations on the files.


What is Disk Scheduling? Type of Disk Scheduling

Disk Scheduling: As we know that on a single Computer we can Perform Many Operations at a Time so that Management is also necessary on all the Running Processes those are running on the System at a Time. With the help or Advent of the Multi-programming we can Execute Many Programs at a Time. So fir Controlling and providing the Memory to all the Processes Operating System uses the Concept of Disk Scheduling.

What is Booting? Type of Booting

Booting: When we start our Computer then there is an operation which is performed automatically by the Computer which is also called as Booting. In the Booting, System will check all the hardware’s and Software’s those are installed or Attached with the System and this will also load all the Files those are needed for running a system.


What is Cache Memory

Cache Memory : The Cache Memory is the Memory which is very nearest to the CPU , all the Recent Instructions are Stored into the Cache Memory. The Cache Memory is attached for storing the input which is given by the user and which is necessary for the CPU to Perform a Task. But the Capacity of the Cache Memory is too low in compare to Memory and Hard Disk.


What is Operating System

Operating System is software that works as an interface between a user and the computer hardware. The primary objective of an operating system is to make computer system convenient to use and to utilize computer hardware in an efficient manner. The operating system performs the basic tasks such as receiving input from the keyboard, processing instructions and sending output to the screen.


Difference between Direct and Indirect Inter-Process Communication

Inter-Process Communication : Cooperating processes can communicate in a shared-memory environment. Cooperating processes communicate with each other via an Inter-Process-Communication (IPC) facility.

What is Shell and Kernel

Both the Shell and the Kernel are the Parts of this Operating System. These Both Parts are used for performing any Operation on the System. When a user gives his Command for Performing Any Operation, then the Request Will goes to the Shell Parts, The Shell Parts is also called as the Interpreter which translate the Human Program into the Machine Language and then the Request will be transferred to the Kernel. So that Shell is just called as the interpreter of the Commands which Converts the Request of the User into the Machine Language. 


What is System Call

As we know that for performing any Operation as user must have to specify the Operation which he wants to Operate on the Computer. We can say that For Performing any Operation a user must have to Request for a Service from the System. For Making any Request a user will prepare a Special call which is also known as the System Call.


What are Multi Tasking, Multi Programming and Multi Threading

Multi programming: Multiprogramming is the technique of running several programs at a time using timesharing. It allows a computer to do several things at the same time. Multiprogramming creates logical parallelism. The concept of multiprogramming is that the operating system keeps several jobs in memory simultaneously.


Functions of Operating System

There are Many Functions those are Performed by the Operating System But the Main Goal of Operating System is to Provide the Interface between the user and the hardware Means Provides the Interface for Working on the System by the user. The various Functions those are Performed by the Operating System are as Explained below:-


Types of Operating System

There are Many Operating Systems those have be Developed for Performing the Operations those are requested by the user. There are Many Operating Systems which have the Capability to Perform the Requests those are received from the System. The Operating system can perform a Single Operation and also Multiple Operations at a Time. So there are many types of Operating systems those are organized by using their Working Techniques.


Write Short Note on First Come First Serve or FCFC

In this Jobs or Processes are Executed in the Manner in which they are entered into the Computer. In thisOperating System Creates a Queue which contains the Sequence Order in which they are to be Executed and the Sequence in which the CPU will Execute the Process.


Write Short Note on Shortest Seek Time First or SSTF

In this Technique The Operating System will Search for the Shortest time means this will search which job will takes a Less Time of CPU for Running. And After Examining all the jobs, all the Jobs are arranged in the Sequence wise or they are Organized into the Priority Order.


Write Short Note on Round Robin.

In the Round Robin Scheduling the Time of CPU is divided into the Equal Numbers which is also called as Quantum Time. Each Process which is Request for Execution will Consumes the Equal Number of Times of the CPU and after the Quantum Time of First Process, the CPU will automatically goes to the Next Process.


Write Short Note on C-Scan Scheduling

In the C-Scan all the Processes are Arranged by using Some Circular List. Circular List is that in which there is no start and end point of the list means the End of the List is the Starting Point of the list. In the C-Scan Scheduling the CPU will search for the Process from Start to end and if an End has Found then this again start from the Starting Process.


What is MUTEX

Mutex is a program object that allows multiple program threads to share the same resource, such as file access, but not simultaneously. When a program is started a mutex is created with a unique name. After this stage, any thread that needs the resource must lock the mutex from other threads while it is using the resource. The mutex is set to unlock when the data is no longer needed or the routine is finished.

What is Fragmentation? Different Types of Fragmentation

Fragmentation occurs in a dynamic memory allocation system when many of the free blocks are too small to satisfy any request.


What is Semaphore

Semaphores are often used to restrict the number of threads than can access some (physical or logical) resource.

What is Process ? Explain Process Scheduling

A Single Process may also contain sub Processes those are also known as the Child Process. So that we can say that a Process which is given to the System is also known as the Parent Process and all the other Parts of the Single Process are known as the Child Process. So that Every Process may also Contains Some Child process.

Explain Various Process States

A process which is Executed by the Process have various States, the State of the Process is also called as the Status of the process, The Status includes whether the Process has Executed or Whether the process is Waiting for Some input and output from the user and whether the Process is Waiting for the CPU to Run the Program after the Completion of the Process.


What do you mean by Process Management

Process: Process is the job which is the under Execution. Process is also known as the Running Job. For Execution there must be a System call which call the Processor or CPU for Performing any Operation. Process includes reading data from a File, Writing a Data from a File, Printing a document means to Say any Type of Operation is known as the Process. Every Process has some Attributes Like


How Deadlock Prevention & Avoidance

After Detecting the Deadlock, we must have to Apply Some Conditions for Removing a Deadlock. After Examining the Four Conditions which Occurs deadlock. Means Detect how and why a deadlock has occurred. Avoidance and Prevention means handle the Deadlock or Remove the Deadlock. Or Make a Program to handle the Deadlock. Various Ways for handing a deadlock.

What is Dead Lock

Dead-Lock is occurred in multiple users Computing Environment. As we know that there is Many Number of users those are going to perform their Transactions. Dead-Lock has occurred when two or More Users are requesting for data item or for a Resource of System for example two or more users Request for the Printers at a Same Time and When Dead-Lock has occurred.

What is the difference between a ‘thread’ and a ‘process’

A process is a collection of virtual memory space, code, data, and system resources. A thread is code that is to be serially executed within a process. A processor executes threads, not processes, so each application has at least one process, and a process always has at least one thread of execution, known as the primary thread.


Describe the Commands in DOS? Name the Commands with their Syntax

DOS commands are small programs, which are made to perform a particular job. Every DOS command performs different task. It is not possible to work on the computer without these commands. There are two types of DOS command.


Explain various Computer Languages

Languages are used for Communication with the System. As we know that there are also Some Human Languages  like English, Punjabi and Hindi those are used for Communicating with the Other Humans. As we know that different Humans Understands different Languages.

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