Welcome back! In the previous lessons, you learned to use IF
statements for decision-making and the EVALUATE
statement for more complex decision paths in COBOL. Now, let's take it a step further by discussing nested IF
statements. This lesson will help you understand how to use nested IF
statements to create more sophisticated decision-making structures in your COBOL programs.
Nested IF
statements allow you to handle multiple layers of conditions in a hierarchical manner. This is particularly useful when dealing with complex logic that requires several conditions to be checked before making a decision. In this lesson, we'll cover:
IF
statementsIF
statements in actionHere’s a snippet of COBOL code to demonstrate:
cobol1IDENTIFICATION DIVISION. 2PROGRAM-ID. NestedIfDemo. 3DATA DIVISION. 4WORKING-STORAGE SECTION. 501 Account-Balance PIC 9(6) VALUE 0. 601 Minimum-Balance PIC 9(6) VALUE 1000. 701 Account-Status PIC X(13). 8PROCEDURE DIVISION. 9 MOVE 500 TO Account-Balance. 10 IF Account-Balance > 0 11 IF Account-Balance < Minimum-Balance 12 MOVE "Low Balance" TO Account-Status 13 ELSE 14 MOVE "Good Standing" TO Account-Status 15 END-IF 16 ELSE 17 MOVE "Overdrawn" TO Account-Status 18 END-IF. 19 DISPLAY "Account Status: " Account-Status. 20 STOP RUN.
In this example:
Account-Balance
is greater than zero.Account-Balance
is indeed greater than zero, we check if it is less than the Minimum-Balance
.Account-Balance
, we then update the Account-Status
accordingly.By nesting IF
statements, you can handle more complex decision trees efficiently. This method is ideal when multiple related conditions need to be evaluated step-by-step.
Also, pay attention to the fact that the nested END-IF
statement doesn't have a period at the end, unlike the primary END-IF
statement. In COBOL, a period signifies the end of a logical block of code, such as a statement, a paragraph, or even an entire section. When you use a period at the end of an IF statement, it tells the compiler that the IF block is complete and that execution should continue with the next independent statement. This can be problematic in nested IF statements because it might terminate the inner block prematurely, leading to incorrect logic.
Mastering nested IF
statements is crucial for several reasons:
IF
statements enable you to handle such complexity.IF
statements help you avoid writing redundant code by organizing your decision-making logic in a hierarchical manner.IF
statements help you identify the problematic condition more easily.Imagine you are building a banking application to update account statuses based on their balance. Using nested IF
statements, as shown in the example, helps you achieve this in an organized, clear, and efficient manner.
Ready to enhance your decision-making logic with nested IF
statements? Let's dive into the practice section and apply these concepts together!