Memory Concepts

Variable names such as number1, number2 and sum actually correspond to locations in the computer's memory. Every variable has a name, a type, a size and a value.

In the addition application of Fig. 3.18, when the statement (line 16)

number1 = Convert.ToInt32( Console.ReadLine() );

executes, the number typed by the user is placed into a memory location to which the name number1 has been assigned by the compiler. Suppose that the user enters 45. The computer places that integer value into location number1, as shown in Fig. 3.19. Whenever a value is placed in a memory location, the value replaces the previous value in that location and the previous value is lost.

Figure 3.19. Memory location showing the name and value of variable number1.

When the statement (line 20)

number2 = Convert.ToInt32( Console.ReadLine() );

executes, suppose that the user enters 72. The computer places that integer value into location number2. The memory now appears as shown in Fig. 3.20.

Figure 3.20. Memory locations after storing values for number1 and number2.

After the application of Fig. 3.18 obtains values for number1 and number2, it adds the values and places the sum into variable sum. The statement (line 22)

sum = number1 + number2; // add numbers

performs the addition, then replaces sum's previous value. After sum has been calculated, memory appears as shown in Fig. 3.21. Note that the values of number1 and number2 appear exactly as they did before they were used in the calculation of sum. These values were used, but not destroyed, as the computer performed the calculationwhen a value is read from a memory location, the process is nondestructive.

Figure 3.21. Memory locations after calculating and storing the sum of number1 and number2.



    Introduction to Computers, the Internet and Visual C#

    Introduction to the Visual C# 2005 Express Edition IDE

    Introduction to C# Applications

    Introduction to Classes and Objects

    Control Statements: Part 1

    Control Statements: Part 2

    Methods: A Deeper Look


    Classes and Objects: A Deeper Look

    Object-Oriented Programming: Inheritance

    Polymorphism, Interfaces & Operator Overloading

    Exception Handling

    Graphical User Interface Concepts: Part 1

    Graphical User Interface Concepts: Part 2


    Strings, Characters and Regular Expressions

    Graphics and Multimedia

    Files and Streams

    Extensible Markup Language (XML)

    Database, SQL and ADO.NET

    ASP.NET 2.0, Web Forms and Web Controls

    Web Services

    Networking: Streams-Based Sockets and Datagrams

    Searching and Sorting

    Data Structures



    Appendix A. Operator Precedence Chart

    Appendix B. Number Systems

    Appendix C. Using the Visual Studio 2005 Debugger

    Appendix D. ASCII Character Set

    Appendix E. Unicode®

    Appendix F. Introduction to XHTML: Part 1

    Appendix G. Introduction to XHTML: Part 2

    Appendix H. HTML/XHTML Special Characters

    Appendix I. HTML/XHTML Colors

    Appendix J. ATM Case Study Code

    Appendix K. UML 2: Additional Diagram Types

    Appendix L. Simple Types


    Visual C# How to Program
    Visual C# 2005 How to Program (2nd Edition)
    ISBN: 0131525239
    EAN: 2147483647
    Year: 2004
    Pages: 600 © 2008-2020.
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