Introduction To Visual Programming

The Field of visual Programming has grown from a marriage of work in Computer Graphics, Programming languages and Human - Computer Interaction. As the fields of Visual Programming
Languages have matured, more and more interest has been focused on creating robust, Standardized classification for work in this area.

WHAT IS VISUAL BASIC PROGRAMMING LANGUAGE {VB}

Visual Programming Language refers to any programming language that allows the user to specify a program in two or more dimensional ways. Conventional textual languages are not considered two-dimensional since the compilers and interpreters process them as one dimensional stream of characters . A Visual Programming Language allows Programming with Visual Expressions.

Visual Programming language may be further classified, according to the type and extent of visual expression used, into icon-based languages, form-based languages and diagram languages. Visual programming environment provides graphical or iconic elements which can be manipulated by the user in an interactive way according to some specific spatial grammar for program construction.

Visual Basic , Visual C++ and Entire Microsoft Visual family are not considered as Visual programming Languages. They are Textual Languages that use a graphical GUI Builder to make programming interfaces easier. The user interface portion of programming environment is visual ,the language are not . Because of the confusion caused by multiple meanings of Visual Programming, Fred Lakin proposed the term "executable graphics" as alternative to VPL .

Example of Visual Programming Languages are :-

* Prograph
* Pict
* Tinkertory
* Fabrik
* CODE 2.0 
* HyperPascal

In Fact, a typical Visual Programming includes the concept of a conventional programming language or Structured programming- Such as C / Pascal , Object Oriented Languages like - C++, Java, Event-Driver Programming Languages like - Visual Basic or Visual C++.

VISUAL BASIC AS STRUCTURED PROGRAMMING

Visual Basic Provides Features of Structured Programming. When High Level Programming  Languages were introduced, statements were exected in the order in which they are written in the program. This is called as normal flow of execution of a program. But the programmer's need increased , other programming constructs , such as loops or decision making constructs were introduced. And finally to solve large and complex programs , they were divided into subprograms , also known as modules. If the subprograms are still difficult to manage , they are further divided into Subprograms .

Visual Basic , As Structured programming language involves four basic control Structures -

* Sequential
* Conditional
* Repetition
* Procedures

1 The Sequential Control Structures are composed of statements executed one after another

DATA FLOW DIAGRAM (DFD) of Sequential statements



2. The Conditional Structure Executes different set of statements depending upon certain condition . Examples of conditional structures in Visual Basic are If-Else-Endif and Select-Case Statements

DATA FLOW DIAGRAM (DFD) of Conditional statements



3. The Repetitive structures repeat set of statements while certain conditions are met. Examples of  repetitive statements are loop, do-while loop, do-until loop, while-wend loop.

4. The Procedures enables us to replace a set of statements with a single statement

DATA FLOW DIAGRAM (DFD) of Procedures