IF is the basic conditional statement of most programming languages. It operates in AL much the same as how it works in other languages. The basic structure is as follows: IF a conditional expression is true, THEN execute Statement-1 or (if condition is not true) execute Statement-2. The ELSE portion is optional. The syntax is as follows:
IF <Condition> THEN <Statement-1> [ ELSE <Statement-2> ]
Note that the statements within an IF statement do not have terminating semicolons, unless they are contained in a BEGIN-END framework. IF statements can be nested so that conditionals are dependent on the evaluation of other conditionals. Obviously, you need to be careful with such constructs, because it is easy to end up with convoluted code structures that are difficult to debug and difficult for the developers following us to understand. In the next chapter, we will review the CASE statement that can make some complicated conditionals...