computer world

  Round-Robin Scheduling in operating system-computer world Round-Robin Scheduling  The round-robin(R-R Scheduling) Scheduling algorithm is designed for time sharing operating system. Round-Robin is similar to FCFS Scheduling, but preemption is added to enable the system to switch between processes. In Round-Robin Scheduling a small unit of time is used which is called a time quantum or time slice. A time quantum is generally from 10 to 100 millisecond. The CPU Scheduler goes around the ready queue, allocate the CPU to every process for a time interval of up to 1 time quantum. In this scheduling new processes are added to the tail of the ready queue. The CPU scheduler picks the first process from ready queue, set a timer after one time slice and dispatch the process. One of two things will happens. When a process have CPU burst of less the 1 time quantum. In this case the process itself release the CPU. If the CPU burst time of the currently running process is longer then one time quan

  Advantage of DBMS Recovery and backup :  Data is secure in DBMS , DBMS provides backup for the system which can be stored later.  Access privilege :  DBMS can store data in single or multiple table and provide access controlling ti the users.  Integrity :  In practical Life, there are ma y situations where multiple user update the same data at the same time. DBMS can supports concurrent transactions so that integrity of data is improved.  Common standards :  DBMS follow common standards for all types of data. Easy to reserve : We can easily retrieve any data from the database. Easy to insert : We can insert new record or data. Easy to delete : If we want to delete unwanted data then DBMS provide facility of deletion.  Security : DBMS provides high level security mechanisms like decryption, password, face and finger detection, voice recognizance. Cost of development : The initial cost of setting up a database can be large.   Disadvantage of DBMS Professionals :  For development of

 Shortest job next scheduling  Shortest job Next Scheduling (SJN) is also known as shortest job first(SJF). In SJF Scheduling the processes which have the smallest execution time is chosen for the next execution. When the CPU is available, it is assigned to the process that has the smallest next CPU burst. If the next CPU burst of two processes is same then FCFS Scheduling is used to break the tie. SJF Scheduling gives the minimum average waiting time fir a given set of processes. Moving a short process before a long process the waiting time of short process more then it increase the waiting time of long process so the average waiting time decrease.  Process.                                  Burst time A1                                                 6 A2                                                 8 A3                                                 7 A4                                                 3 The waiting time for process A1 = 3 millisecond  The waiting time for proces

  First-come, First-served Scheduling In this scheduling algorithm simply the jobs according to their arrival time which job come first in the queue will get the CPU first. It means the process(job) that requests the CPU first is allocate the CPU first. The FCFS policy is simply and easily managed with a FIFO(First in First out) queue. When a process enter in the ready, its PCB is linked onto the tail of the queue. When the CPU is free, it allocated to the process at the head if the queue. The code for FCFS scheduling is very simple to understand. On the negative side, the average waiting time under the FCFS policy is long. The CPU has been allocated to a process, that process keeps CPU its processing is not complete. So the CPU in this scheme is scheduled to the process in the order of arrival at the ready queue it is the simplest CPU scheduling algorithm.  1. Turn around time : Turn around time is the time taken by a process between ready queue and finishing execution. 2. Wait time :

  CPU scheduling in operating system CPU scheduling :  Whenever the CPU becomes idle, the operating system must select one of the processes. The selection process is carried by the short-term scheduler. The scheduler selects a process from the processes in memory that that are ready to execute and allocate the CPU to that process. The objective of time sharing is to skip the CPU among processes that user interact with each program while the program is in running position. As we discuss above the process scheduler selects an process for execution on the CPU. There will never more then one running process for a single processor system. If there are many processes, the process will have to wait until the CPU is free CPU Scheduling is basis of multi-programming operating system. In CPU scheduling many processes are kept in memory at a time. The CPU scheduler select a process from the many processes. The process scheduler scheduled different processes to be assigned to the CPU based on part

Process's hierarchy in operating system-computer world Process's hierarchy :  In operating system process are arranged in a hierarchical manner. Some process are controlling some another process these process are called parent process. In other word we can say that modern operating system are used to create or destroyed process. The creating process is known as parent process and the new process are called child process. A parent process have many child process but the child process has only one parent process.  Hierarchical structure : The operating system is designed in a manner that a parent process has the block of a child process each child is ultimately under the full control of parent process and this structure is called the hierarchical structure of the process existing in a system.    Modern general purpose operating system permit a user to create and destroy processes  In Unix this is done by the the fork system call.  After a fork both parent and child keep running a

Macros and Mail merge in ms word Macros Macro are advance features that can speed up editing or formatting you may perform often in a word document. They record sequences of menu selection that you choose so that a series of action can be completed in one step. How to records a macro To record a macro Click the view tab on the ribbon  Click macros Click record macro Enter a name(without space) Click whether you want it assigned to a bottom (on the quick access toolbar) or the keyboard (a sequence of key ) To assign the macro a button on the quick access toolbar Click button Under the customize quick access toolbar , select the document for which you want the macro available. Click the macro that you are recording Click add Click OK to begin recording the macro Perform the action you want recorded in the macro Click the macro Click on stop recording macro Running a macro  To run a macro from the quick Access toolbar, Simply click on macro icon.   Mail merge  A mail merge method of takin

                             Direct memory access  Direct memory access :  DMA stands for  direct memory access and it is another mechanism where input output device is given full transfer block of data to from memory without going through the CPU. In other word we can say that it is a method of transferring data from the computers RAM to another part of computer. The DMA controller operate the memory bus directly without the help of main CPU so DMA controller improves the system performance. Whenever a device uses DMA , it has to specify a DMA channel . Ultra DMA hard drive uses DMA to transfer at high speed. Whereas earlier hard drives were the first to transfer data from CPU which took more time.  In older computers , the four DMA channel were 0, 1, 2 and 3 were used , when the 16 bit ISA bus was introduced, the channels 5, 6 and 7 were also added to it. DMA transfer modes 1. Burst mode : Burst mode is the fastest DMA mode in which two or more bytes can be continuously transferred.

 What is plotter and different types of plotter   Plotter  Plotter is used for an ideal output devices like engineering, city planner and others who need hard copy output of different size. We know that printers are used for graphics output but many engineers requires high quality output on large sheet.  Two commonly used plotters are  Drum plotter Flatbed plotter Ink jet plotter 1. Drum plotter :  in a drum plotter the paper on which the design is to be made is placed a the drum that can rotate in both clockwise and anticlockwise it produce vertical motion. The machine is also  consist of one or more pen holder connected to the drum surface. The pen can move left to right or right to left produce horizontal motion. The drum and pen move simultaneously to draw design and graphs on the sheet placed on the drum.  2. Flatbed   plotter :  A flatbed plotter plot a design or graphs on a sheet of paper that is fixed over a flatbed tab le. In this type of plotter the paper does not move and t

  Device management in operating system Device management in operating system implies the management of input/output devices such as keyboard, disc ,microphone, scanner etc. There are a variety of input output devices that can be attached to a computer system. We discuss about the element of input output devices and how they interact with the computer system and also discuss about the responsibilities of an operating system. Computer operates on many devices like transmission devices, character devices, multimedia devices etc. Device management is the process of managing the maintenance of physical and virtual devices. The various resources controlled by the operating system can be thought of as devices some of these devices are physical devices and virtual devices, physical devices like keyboard printer Mouse etc Virtual devices like file and device driver.  Device driver : A device driver is a type of software that helps to run any hardware connected to a computer. When we add a devi

Distributed operating system and its Advantage,Disadvantage  Distributed operating system :  The motivation behind developing distributed operating system is the availability of powerful and inexpensive microprocessor and advance in communication technology in this operating system many computer are interconnected by communication networks. Distributed operation system is one of the important type of operating system. These operating system use multiple central processor to serve multiple real time application and multiple user.The processor communicate with one another through various communication lines (Such as high sped buses or telephone lines ). These processor are known as sits, nodes, computers etc. Advantage of distributed operating system :  If one site fail in a distributed system, the remaining sites can potentially continue operate. There are variety of reasons for building distributed system, Resource sharing, computation speed up, reliability, communication. Reduction of

Trap :    A trap is a software generated interrupt caused either by an error (like division by zero, invalid memory access etc.) , Or an by a specific request for an operating system generated by a user program. Trap is sometimes called exception . Its handling is  synchronous .  Interrupt :   An interrupt is something generated by the device like the hard disk graphics card input/output ports etc. These are  asynchronous  or " passive " since the interrupt handler has to wait for them to happen eventually. Interrupt occur at random times during the execution of a program. Software can also generate interrupt by executing the INT instruction. It is important to note that trap and interrupt are closely related. Trap are are a type of exception and exceptions are similar to interrupts.

  Input and output ports advantage and disadvantage Input/output ports Parallel port :  Parallel port is a type of interface found on computers for connecting various peripherals. Data flows through 8 wires simultaneously and transmit 8 bits of data in parallel. Serial port :  A serial port transmits one bit of data through a single wire.serial port is used to connect plotters, Bar-code reader etc. Universal serial port(USB) : It is a common and popular external port available with computers.Normally two to four USB ports are available on the computer. Fire-wire :  Hard disk drive and new DVD drives connect through fir-wire. It is an expansive technology used for large data movement. Advantage of input/output ports :  Parallel port transmit 8 bit of data in parallel. Input/output port are used to connect peripheral device to the computer. A single USB port can support connection of up-to 127 devices. Input/output are used to connect audio and video multimedia devices to the computer.

Various types of primary memory for project Primary memory : Primary memory holds only that data and instruction on which the computer is currently working. It is made up of semiconductor device. In this memory data is lost when power switched of. These memory are not as fast as registers. It is a temporary storage area built into the computer hardware. Physically, this memory consist of some integrated circuit chips either on the motherboard or on a small circuit board attached to a motherboard to a computer system.This memory is divided into two subcategory's :  RAM(Random access memory) ROM(Read only memory)   1. RAM(Random access memory) : RAM consist of some integrated circuits. Computer's motherboard is design in a manner that its memory capacity can be enhanced easily by adding more memory chips.  Random access memory is a form of computer memory that can be read and change in any any order typically used to store working data and machine code. RAM is divided into tw