Release 10.1A: OpenEdge Development:
Progress 4GL Handbook

Procedure Blocks and Data Access

In the first three chapters of this book, you learn about the basic structure of the Progress 4GL and many of its language constructs. The next two chapters focus on the user interface of a GUI application as you learn to use the AppBuilder to build an application window, examining the language syntax that defines the elements in the window along the way. This chapter returns you to writing 4GL procedures on your own. These procedures contain some business logic that demonstrates in detail a few of the concepts touched on in the previous chapters.

The important concepts of this chapter are ones you’ve already seen in action and learned something about. Indeed, as discussed with the very simplest Progress 4GL procedure—FOR EACH Customer: DISPLAY Customer.—you can hardly write any 4GL code at all without defining blocks and using data access statements.

Nonetheless, this chapter goes into a lot more detail in these areas so that you have a more thorough understanding of these basic building blocks of Progress 4GL procedures. In this chapter, you’ll learn:

All the basic syntax for defining blocks of various kinds in the language, including some that iterate through a set of statements and some that just group them as a common action.
About the scoping of blocks and of the variables and objects you define in them and how scoping affects the way your procedures behave.
A variety of ways to access database data and integrate it into your procedures.

This chapter includes the following sections:

Blocks and block properties
Procedure block scoping
Language statements that define blocks