What are the different control structures available in COBOL, and how are they used for decision making and looping?

In COBOL, control structures play a crucial role in decision making and looping within programs. They provide the ability to control the flow of execution based on certain conditions and perform repetitive tasks. Let's explore the different control structures available in COBOL and their usage:

1. IF-ELSE statement:

* The IF-ELSE statement allows for conditional branching in COBOL programs.
* It evaluates a condition and executes a block of code if the condition is true. If the condition is false, an alternative block of code can be executed.
* The ELSE clause is optional and provides an alternative path if the condition evaluates to false.
2. EVALUATE statement:

* The EVALUATE statement is used for multi-way decision making in COBOL.
* It allows the evaluation of a given expression against multiple conditions and executes the corresponding block of code based on the matching condition.
* The WHEN clauses are used to define different conditions and the associated code to be executed when a condition matches.
* The EVALUATE statement provides a more structured and readable approach compared to nested IF-ELSE statements, especially when dealing with multiple conditions.
3. PERFORM statement:

* The PERFORM statement is used for looping or repetitive execution of a block of code.
* It enables the execution of a specific section of code multiple times until a condition is met.
* The condition can be defined using an EVALUATE statement, a simple condition, or a combination of conditions.
* The PERFORM statement can be used with different variations such as PERFORM UNTIL, PERFORM VARYING, and PERFORM THROUGH, allowing for flexibility in loop control.
4. GO TO statement:

* The GO TO statement provides unconditional branching within a COBOL program.
* It allows the program to transfer control to a specific labeled section of the code.
* While the use of GO TO statements is generally discouraged in modern programming practices due to its potential for spaghetti code, it can still be useful in certain scenarios for non-linear control flow.
5. NEXT SENTENCE and CONTINUE statements:

* The NEXT SENTENCE statement is used to skip to the next logical sentence within a paragraph, skipping the remaining code within the current sentence.
* The CONTINUE statement is used to indicate a null operation or no action and is commonly used to improve readability.

These control structures provide powerful mechanisms for decision making and looping in COBOL programs. By utilizing IF-ELSE statements, EVALUATE statements, PERFORM loops, and appropriate branching techniques, developers can effectively control the flow of execution and handle complex logic within COBOL programs. It is important to use these control structures judiciously, ensuring code readability, maintainability, and adherence to best practices.