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Engg.Chemistry

Engg.Physics

Introduction to Computers

  • D. Vijay Kumar

    Asst. Prof., Dept IT

    MGIT, Hyd

         A computer system consists of hardware and software.
    Computer hardware is the collection of physical elements that comprise a computer system. Computer software is a collection of computer programs and related data that provides the instructions for a computer what to do and how to do it. Software refers to one or more computer programs and data held in the storage of the computer for some purposes.
    Basically computer software is of three main types

    1. Operating System
         The Operating System (OS) is an interface between the compute software and hardware. The most popular and latest operating systems include Windows XP, Mac, UNIX, Linux, Windows Vista, etc.
    2. Application Software
         The application software is widely used for accomplishment of specific and precise tasks which is a step ahead than the basic operations or running of the computer system. The application software includes printing documents, and permitting access to internet for web and video conferencing activities. The Application software indirectly does the interaction with the machine to perform all these functions.
    3. System Software
         System software directly interacts with computer hardware. Some of the examples are the device drivers for CPU, Motherboard, Mouse, Printer, Keyboard, etc. The system software takes the responsibility of control, integration and managing individual hardware machine of the computer.
    Computing Environment:
         Computing Environment is a collection of computers / machines, software, and networks that support the processing and exchange of electronic information meant to support various types of computing solutions
    Types of Computing Environments:
    Personal Computing Environment
    Client Server Environment
    Time sharing Environment
    Distributed Environment

    Algorithm:
         An algorithm is a description of a procedure which terminates with a result. Algorithm is a step-by-step method of solving a problem.
    Properties of an Algorithm:

    1. Finiteness: - An algorithm terminates after a finite numbers of steps
    2. Definiteness: - Each step in algorithm is unambiguous. This means that the action specified by the step cannot be interpreted (explain the meaning of) in multiple ways & can be performed without any confusion.
    3. Input: - An algorithm accepts zero or more inputs
    4. Output:- An algorithm should produce at least one output.
    5. Effectiveness: - It consists of basic instructions that are realizable. This means that the instructions can be performed by using the given inputs in a finite amount of time.

    Flowchart:
         A flowchart is a graphical or pictorial representation of an algorithm.
    Each step in the process is represented by a different symbol and contains a short description of the process step. The flow chart symbols are linked together with arrows showing the process flow direction. Some common flowcharting symbols are listed below

     

    Purpose

    Symbol

    Terminator

    An oval flow chart shape indicating the start or end of the process.

    Process

    A rectangular flow chart shape indicating a normal process flow step.

    Decision

    A diamond flow chart shape indication a branch in the process flow.

    Connector

    A small, labeled, circular flow chart shape used to indicate a jump in the process flow.

    Data

    A parallelogram that indicates data input or output (I/O) for a process.


    Program Development Steps:
    1. Statement of Problem
    a) Working with existing system and using proper questionnaire, the problem should be explained clearly.
    b) What inputs are available, what outputs are required and what is needed for creating workable solution, should be understood clearly.
    2. Analysis
    a) The method of solutions to solve the problem can be identified.
    b) We also judge that which method gives best results among different methods of solution.
    3 .Design
    a) Algorithms and flow charts will be prepared.
    b) Focus on data, architecture, user interfaces and program components
    4 .Implementation
         The algorithms and flow charts developed in the previous steps are converted into actual programs in the high level languages like C.
    a. Compilation
         The process of translating the program into machine code is called as Compilation. Syntactic errors are found quickly at the time of compiling the program. These errors occur due to the usage of wrong syntaxes for the statements
    Eg: x=a*y+b
         There is a syntax error in this statement, since, each and every statement in C language ends with a semicolon (;).
    b. Execution
         The next step is Program execution. In this phase, we may encounter two types of errors. Runtime Errors: these errors occur during the execution of the program and terminate the program abnormally.
    Logical Errors: these errors occur due to incorrect usage of the instructions in the program. These errors are neither detected during compilation or execution nor cause any stoppage to the program execution but produces incorrect output

    General Structure of a C program:

    /* Documentation section */ /* Link section */
    /* Definition section */
    /* Global declaration section */ main()
    {
    Declaration part
    Executable part (statements)
    }
    /* Sub-program section */

    The documentation section is used for displaying any information about the program like the purpose of the program, name of the author, date and time written etc, and this section should be enclosed within comment lines. The statements in the documentation section are ignored by the compiler.
    The link section consists of the inclusion of header files.
    The definition section consists of macro definitions, defining constants etc,.
    Anything declared in the global declaration section is accessible throughout the program, i.e. accessible to all the functions in the program.
    Main() function is mandatory for any program and it includes two parts, the declaration part and the executable part.
    The last section, i.e. sub-program section is optional and used when we require including user defined functions in the program.

    Important Questions from UNIT 1 and Answers
    1. Briefly discuss various computing environments with neat diagrams?
    Ans: In the early days of computers, there was only one environment: the main frame computer hidden in a central computing department. With the advent of mini computers and personal computers, the environment changed, resulting in computers on virtually every desktop.

    Personal Computing Environment

         In 1971,Marcian E.Hoff, working for Intel, combined the basic elements of the central processing unit into the microprocessor. The first computer on a chip was the Intel 4004 and was the grandparent many times removed of Intel's current system.

         If we are using a personal computer, all of the computer hardware components are tied together in our personal computer(PC).


    Time-Sharing Environment

         Employees in large companies often work in what is known as a time-sharing environment. In the times-sharing environment, many users are connected to one or more computers. These computers may be minicomputers or central mainframes. The terminals they use are often nonprogrammable, although today we see more and more microcomputers being used to simulate terminals. Also, in the time-sharing environment, the output devices and auxiliary storage devices are shared by all of the users. A typical college lab in which a minicomputer is shared is shared by many students is shown in figure :

    In the time- sharing environment ,all computing must be done by the central computer. The central computer has many duties: It must control the shared resources; it must manage the shared data and printing and it must do the computing.
    Client / Server Environment
         A client / servercomputing environment splits the computing function between a central computer and users’ computers. The users are given personal computers or work stations so that some of the computation responsibility can be moved from the central computer and assigned to the workstations. In the client-server environment, the users’ micro computers or workstations are called the client. The central computer, which may be a powerful microcomputer, minicomputer, or central mainframe system, is known as the server. Because the work is now shared between the users’ computers and the central computer, response time and monitor display are faster and the users are more productive.

    Distributed Computing

         A Distributed Computing environment provides a seamless integration of computing functions between different servers and clients .The internet provides connectivity to different servers throughout the world. For example eBay uses several computers to provide its auction services. This environment provides a reliable, scalable, and highly available network.
    Fig: Distributed Computing


    2. Define Algorithm? What are the characteristics that any algorithm should satisfy?
    Ans:
    Algorithm:
         An algorithm is a description of a procedure which terminates with a result. Algorithm is a step-by-step method of solving a problem.
    Properties of an Algorithm:
    1. Finiteness: - An algorithm terminates after a finite numbers of steps
    2. Definiteness: - Each step in algorithm is unambiguous. This means that the action specified by the step cannot be interpreted (explain the meaning of) in     multiple ways & can be performed without any confusion.
    3. Input: - An algorithm accepts zero or more inputs
    4. Output:- An algorithm should produce at least one output.
    5. Effectiveness: - It consists of basic instructions that are realizable. This means that the instructions can be performed by using the given inputs in a finite     amount of time.
    3.Define Flow Chart ? What are the various components in flow chart?
    Ans:
    Flowchart:
         A Flow chart is a Graphical representation of an Algorithm or a portion of an Algorithm. Flow charts are drawn using certain special purpose symbols such as Rectangles, Diamonds, Ovals and small circles. These symbols are connected by arrows called flow lines.

     

    Purpose

    Symbol

    Terminator

    An oval flow chart shape indicating the start or end of the process.

    Process

    A rectangular flow chart shape indicating a normal process flow step.

    Decision

    A diamond flow chart shape indication a branch in the process flow.

    Connector

    A small, labeled, circular flow chart shape used to indicate a jump in the process flow.

    Data

    A parallelogram that indicates data input or output (I/O) for a process.

     

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