Program structure in vb 6.0

You cannot redefine this behavior. Because structures are value types, each structure variable is permanently bound to an individual structure instance. But classes are reference types, and an object variable can refer to various class instances at different times.

This distinction affects your usage of structures and classes in the following ways:. A structure variable implicitly includes an initialization of the elements using the structure's parameterless constructor. Assigning Variables. When you assign one structure variable to another, or pass a structure instance to a procedure argument, the current values of all the variable elements are copied to the new structure.

When you assign one object variable to another, or pass an object variable to a procedure, only the reference pointer is copied. Assigning Nothing. You can assign the value Nothing to a structure variable, but the instance continues to be associated with the variable. You can still call its methods and access its data elements, although variable elements are reinitialized by the assignment. In contrast, if you set an object variable to Nothing , you dissociate it from any class instance, and you cannot access any members through the variable until you assign another instance to it.

Multiple Instances. An object variable can have different class instances assigned to it at different times, and several object variables can refer to the same class instance at the same time. A While Wend statement behaves like the Do While Loop statement. The following While Wend counts from 1 to The Do Loop While statement first executes the statements and then test the condition after each execution.

The following program block illustrates the structure:. The programs executes the statements between Do and Loop While structure in any case. Then it determines whether the counter is less than If so, the program again executes the statements between Do and Loop While else exits the Loop.

Unlike the Do While Loop and While Wend repetition structures, the Do Until Loop structure tests a condition for falsity. Statements in the body of a Do Until Loop are executed repeatedly as long as the loop-continuation test evaluates to False.

An example for Do Until The coding is typed inside the click event of the command button. Numbers between 1 to will be displayed on the form as soon as you click on the command button.

The For Next Loop is another way to make loops in Visual Basic. Next repetition structure handles all the details of counter-controlled repetition.

Contents Exit focus mode. Is this page helpful? Please rate your experience Yes No. Any additional feedback? Submit and view feedback for This product This page. View all page feedback. In this article. Visual Basic Naming Conventions Includes general guidelines for naming procedures, constants, variables, arguments, and objects. Visual Basic Coding Conventions Reviews the guidelines used in developing the samples in this documentation.

Conditional Compilation Describes how to compile particular blocks of code selectively while directing the compiler to ignore others. How to: Break and Combine Statements in Code Shows how to divide long statements into multiple lines and combine short statements on one line. How to: Label Statements Shows how to mark a line of code to identify it for use with statements such as On Error Goto.

Special Characters in Code Shows how and where to use non-numeric and non-alphabetic characters. Comments in Code Discusses how to add descriptive comments to your code.