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Defining and accessing global variables in memory

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• Simple and compound variables
  • Simple variables:

    Simple variable = a variable in a program that is referred to by a simple (= non-compound) identifier

    Examples:

    int a; float b; short s;

    The variables a, b and s are simple variables

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  • Non-simple variable or compound variable:

    a variable that consist of multiple parts

    Examples:

    Array: an array consists of multiple array elements Object: an object has multiple components Example: public class BankAccount { int AccNumber; double balance; }

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• Global variables
  • Global variable:

    Global variable = a variable that is: created when the program begins to execute is accessible (= can be used) anywhere in the program

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• The Java programming language and global variables
  • In Java, the following kind of variables are global variables:

    public Class variables

    Example:

    public class myClass { public static int x; // A public class variable ... }

    Fact:

    The variable x is a global variable

    Because:

    The variable x is created when the Java program begins to execute The variable x is accessible (= can be used) anywhere in the Java program by using the following expression: myClass.x

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• Defining simple global variables using assembler
  • From what we have seen previously, you can define simple global variable of different data types as follows:

    Byte: Java syntax | equivalent assembler construct -------------------+------------------------------------- byte varName; | varName: ds.l 1

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