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Event Driven Programming

A tiny box holding a minus sign will appear to the left of the #Region line. To collapse the code,
click on the minus sign. The code will be hidden behind a rectangle captioned with the text you
specified and the minus sign will be replaced by a plus sign. Click on the plus sign to expand
the region. The Region directive is used to make a program more readable or to create an outline
for a program. In Figure 8.1(a), Region directives have been specified for each Procedures in
Example . In Figure 8.1(b), these two regions have been collapsed.

Figure 8.1(b): Collapsed Region.

8.6 Modules

Full-featured software usually requires large programs. Writing the code for an event procedure
in such a Visual Basic program might pose a complicated problem. One method programmers
use to make a complicated problem more understandable is to divide it into smaller, less
complex subproblems. Repeatedly using a “divide-and-conquer” approach to break up a large
problem into smaller subproblems is called stepwise refinement. Stepwise refinement is part of
a larger methodology of writing programs known as top-down design. The term top-down refers
to the fact that the more general tasks occur near the top of the design and tasks representing
their refinement occur below. Top-down design and structured programming emerged as tech-
niques to enhance programming productivity. Their use leads to programs that are easier to read
and maintain. They also produce programs containing fewer initial errors, with these errors
being easier to find and correct. When such programs are later modified, there is a much smaller
likelihood of introducing new errors.
The goal of top-down design is to break a problem into individual tasks, or modules, that can
easily be transcribed into pseudocode, flowcharts, or a program. First, a problem is restated as

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