2.3.2 What Is Different Between Event-Driven and Procedural Programs?

There are some fundamental differences in how event-driven and procedural programs are designed and executed:

• In Visual LANSA you create the graphical user interface using controls which have powerful built-in functionality such as tree views, tabbed folders, video and animation.
  
  In a LANSA function you have very limited graphical controls in order to accommodate non-graphical platforms.

• In Visual LANSA you create the interface of the program graphically by dragging controls to a form which corresponds to a window of the application when it is running.
  
  In a LANSA function you create the interface programmatically using DISPLAY, REQUEST and POP_UP statements.

• In an event-driven program you write code for the individual controls, for example a button. So your application consists of many event routines. These event routines are executed individually which makes it possible for the individual controls on the form to respond dynamically to user actions.
  
  A LANSA function is one program which runs from the beginning to the end. A screen is always processed as a whole so it cannot change dynamically.

When executing Visual LANSA applications you perform actions directly on objects.

In Universal UI functions you first choose an action, such as Add, which sets a mode in the program and then work on the object.

Also see

The Code Is Always Associated With a Component

Modes Are Not Needed because Actions Are Performed Directly

The Code for a Mode Often Becomes an Event Routine

Sequence of Actions Is Free

You Create the Interface Graphically