bdfs1m0cStructured Programming Macros

An Overview of Structured Forms

In structured programming theory, only three basic control logic structures are required to program any function:

A sequence is the processing of one function after the other, as shown in Figure 1. No special logic is required because processing is always sequential.

Figure 1. Sequence: Processing Code Sequentially


A selection is the choice between two or more functions to be processed based on a condition.

For example, the IF macro group, shown in Figure 2, is used for selection.

Figure 2. Selection: Using a Condition


The CASE macro group, shown in Figure 3, is another example of a macro group used for selection.

Figure 3. Selection: Using a Case Number


An iteration is the repeated processing of the same code while, or until, a condition is true, as shown in Figure 4.

Figure 4. Simple Iteration: The Difference between DO WHILE and DO UNTIL


Notes:

  1. The code can be bypassed (never processed) if condition is false on entry to the DO WHILE loop.

  2. The code is processed at least once before the DO UNTIL condition is tested.