9th Class

   Multitasking OS   Operating systems that allow multiple software processes to be run at the same time is called multitasking OS, such as Microsoft Windows XP and Linux. It means multitasking operating systems allow a user to do more than one thing at the same time. For example, when working on Windows operating system, you can listen to music and work on MS Word simultaneously. This is one of the best examples of multitasking OS.      OS as Resource Manager Operating system works as a resource manager. It involves the following

• Process management
• Multiprogramming
• Memory Management
• Spooling  

    Process Management In computer science process is a program execution. During program execution, a process needs various resources such as CPU time, memory space, files and I/O devices. At a particular instance of more...

     Structure of OS   The internal structure of operating system is divided into layers. The outermost layer is called user interface and innermost layer is hardware.      The following are the main layers in OS: 

• Kernel
• Shell
• User Interface  

    Kernel Kernel is a central controlling part of OS that implements the most primitive of the system's functions. This part cannot be replaced or modified by user. Basically kernel performs basic function for memory management, device management, low level security and process management.      Shell Shell is a part of software that serves as a user interface it forms the outer layer of an operating system covering the other modules of the operating system. The shell can be a command-line interface or GUI (Graphical User more...

  Operating System   An Operating System is a master control program. Basically it is system software that manages the operation of a computer. Without an operating system computer cannot work. The computer is useless unless it is provided with essential software that makes it ready to use. As we have seen that an operating system is software, which makes the computer ready to use by a process called booting. Basically booting is a process which loads operating system from disk to RAM. About twenty years ago Steve Jobs and Wozniak, the founders of Apple, came up with the very strange idea of selling information processing machines for use at the home. The business took off, and its founders made a lot of money and received the credit they deserved for being daring visionaries. But around the same time, Bill Gates and Paul Alien came up more...

    Storage Media          Magnetic Tape Magnetic tape is storage medium. Basically it consists of a thin tape with a coating of a fine magnetic material. It is used for recording analogue or digital data, such as audio video. Data is stored in frames and the frames are grouped into blocks which are separated from other blocks by some free spaces. Magnetic tape allows sequential technique for searching records. It similarly works like audio and video cassette. Storing data on tapes is considerably cheaper than storing data on disks. Accessing data on tapes, however, is much slower than accessing data on disks. The following figure shows magnetic tape:       Hard Disk The hard disk is another type of permanent storage media that is used to store huge volume of data. It is more...

    Data Access Methods   In computer science data access method is a hardware mechanism or computer program that moves data between the computer and storage device, such as hard disk, floppy and CD. Basically there are two types of data access methods.       They are the following: 

• Sequential Access Method
• Direct Access Method  

    Sequential Access Method In this method records must be read in the same order as they were written to the storage media. The computer begins searching for a record in the file and then sequentially examining the next record and so on until the required record is located. The best example of these kinds of storage media is magnetic tape. The magnetic tape allows only sequential access to data. While searching a record on a reel more...

      Number system   The number of digits in the system determines the base of any number system, such as decimal and binary. Basically binary is a base -2 number system as it uses two basic digits. Thus it means that the whole Binary number system depends on the two basic digits. Whereas Decimal is a base-10 system since it uses ten digits and these are 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9.      Decimal Number System A system with base - 10 is a decimal number system. Thus it means that there are ten basic digits on which the decimal number system depends. The digits are 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. By using these ten digits all the numbers in decimal number system are written. Thus the place more...

   Classification of Computers         Micro Computers Micro Computer is a computer whose CPU (Central Processing Unit) is a microprocessor. All the components of a microprocessor are on a single integrated circuit chip. Micro computer can be categorized I as the desktop, programmable and workstation. The microprocessor based computers are called third generation computers. They are the backbone of the modern computer era. The first and second generation computers are based on vacuum tubes and bipolar junction transistors. In the early 1970s, minicomputers carried the work, based on integrated circuits but too large to be called microcomputers. In 1974, Intel released the Intel 8080. It was the first usable microprocessor. In 1980s microcomputer began to slowly edge out. (See Figure. 9.1.1)                                                                                         Mini more...

   

Recently a cyclone has hit some of the areas in your town. Write a letter to your friend in Mumbai stating him/her about the damage made by the impact of the cyclone.

Write a letter to your friend inviting him/her to come to your place during summer vacation and spend a few days with you.

You have been to an excursion in the mountain areas of Garwal. Write a letter to your cousin in Bangalore stating him/her about the scenic beauty of the area and your experience during the excursion.

You have undertaken a railway journey from Delhi to Nander. Write a letter to your friend stating him/her about the experience of the journey.

Write a letter to the Editor of a leading newspaper stating about the irregular supply of drinking water in your area.

You have booked a railway ticket more...

       Letters   Introduction: Letters can be broadly classified into formal letters and informal letters. Formal letters include business letters, official letters, applications, complaints, letter to editors, and letters written to people whom we want to convey certain important information. While, informal letters include personal letters, letters that are written to our friends and family. Letter writing is a skill that needs to be honed over time with practice.           1.    You are Shekhar and study in a residential school in Darjeeling. Write a letter to your father in Kolkata informing him about your result in Half-yearly Examination.                                                                         more...

    Write a paragraph on each the following topics in not more than 250 words.   1.             A cell phone 2.             A treasured belonging 3.             Your memory of a place that you visited as a child 4.             An embarrassing experience 5.             The breakup of a friendship 6.             The act of heroism or cowardice 7.             A memorable journey 8.             An experience that taught you a lesson 9.             How to develop self-confidence? 10.           The values of science            

• The first sentence of a paragraph should be a topic sentence and should contain the topic and an opinion on the topic.
• Write down the subject of your paragraph. To express your subject, write only a word or phrase.
• Begin by brainstorming. Brainstorming doesn't involve writing more...