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Operators and Expressions

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In this section, we will delve into the fundamental concepts of operators and expressions in RPG programming. Understanding these concepts is crucial as they form the basis for performing calculations, making decisions, and manipulating data within your programs.

Key Concepts

  1. Operators: Symbols that perform operations on variables and values.
  2. Expressions: Combinations of variables, values, and operators that yield a result.

Types of Operators

  1. Arithmetic Operators

Arithmetic operators are used to perform mathematical calculations.

Operator Description Example
+ Addition A + B
- Subtraction A - B
* Multiplication A * B
/ Division A / B
** Exponentiation A ** B

  1. Relational Operators

Relational operators are used to compare two values.

Operator Description Example
= Equal to A = B
<> Not equal to A <> B
> Greater than A > B
< Less than A < B
>= Greater than or equal to A >= B
<= Less than or equal to A <= B

  1. Logical Operators

Logical operators are used to combine multiple conditions.

Operator Description Example
AND Logical AND A AND B
OR Logical OR A OR B
NOT Logical NOT NOT A

  1. Assignment Operators

Assignment operators are used to assign values to variables.

Operator Description Example
= Assign A = B
+= Add and assign A += B
-= Subtract and assign A -= B
*= Multiply and assign A *= B
/= Divide and assign A /= B

Practical Examples

Example 1: Arithmetic Operations

DCL-S A INT(10);
DCL-S B INT(10);
DCL-S Result INT(10);

A = 10;
B = 5;

Result = A + B; // Result is 15
Result = A - B; // Result is 5
Result = A * B; // Result is 50
Result = A / B; // Result is 2
Result = A ** B; // Result is 100000

Example 2: Relational Operations

DCL-S A INT(10);
DCL-S B INT(10);
DCL-S IsEqual IND;

A = 10;
B = 5;

IsEqual = (A = B); // IsEqual is *OFF
IsEqual = (A <> B); // IsEqual is *ON
IsEqual = (A > B); // IsEqual is *ON
IsEqual = (A < B); // IsEqual is *OFF
IsEqual = (A >= B); // IsEqual is *ON
IsEqual = (A <= B); // IsEqual is *OFF

Example 3: Logical Operations

DCL-S A IND;
DCL-S B IND;
DCL-S Result IND;

A = *ON;
B = *OFF;

Result = A AND B; // Result is *OFF
Result = A OR B; // Result is *ON
Result = NOT A; // Result is *OFF

Example 4: Assignment Operations

DCL-S A INT(10);
DCL-S B INT(10);

A = 10;
B = 5;

A += B; // A is 15
A -= B; // A is 10
A *= B; // A is 50
A /= B; // A is 10

Practical Exercises

Exercise 1: Basic Arithmetic

Write a program that calculates the sum, difference, product, and quotient of two numbers.

DCL-S Num1 INT(10);
DCL-S Num2 INT(10);
DCL-S Sum INT(10);
DCL-S Difference INT(10);
DCL-S Product INT(10);
DCL-S Quotient INT(10);

Num1 = 20;
Num2 = 4;

Sum = Num1 + Num2;
Difference = Num1 - Num2;
Product = Num1 * Num2;
Quotient = Num1 / Num2;

DSPly ('Sum: ' + %Char(Sum));
DSPly ('Difference: ' + %Char(Difference));
DSPly ('Product: ' + %Char(Product));
DSPly ('Quotient: ' + %Char(Quotient));

Exercise 2: Relational and Logical Operations

Write a program that checks if a number is within a specified range and if it is even.

DCL-S Num INT(10);
DCL-S IsInRange IND;
DCL-S IsEven IND;

Num = 15;

IsInRange = (Num >= 10 AND Num <= 20);
IsEven = (Num MOD 2 = 0);

DSPly ('Is in range: ' + %Char(IsInRange));
DSPly ('Is even: ' + %Char(IsEven));

Solutions

Solution 1: Basic Arithmetic

DCL-S Num1 INT(10);
DCL-S Num2 INT(10);
DCL-S Sum INT(10);
DCL-S Difference INT(10);
DCL-S Product INT(10);
DCL-S Quotient INT(10);

Num1 = 20;
Num2 = 4;

Sum = Num1 + Num2;
Difference = Num1 - Num2;
Product = Num1 * Num2;
Quotient = Num1 / Num2;

DSPly ('Sum: ' + %Char(Sum));
DSPly ('Difference: ' + %Char(Difference));
DSPly ('Product: ' + %Char(Product));
DSPly ('Quotient: ' + %Char(Quotient));

Solution 2: Relational and Logical Operations

DCL-S Num INT(10);
DCL-S IsInRange IND;
DCL-S IsEven IND;

Num = 15;

IsInRange = (Num >= 10 AND Num <= 20);
IsEven = (Num MOD 2 = 0);

DSPly ('Is in range: ' + %Char(IsInRange));
DSPly ('Is even: ' + %Char(IsEven));

Common Mistakes and Tips

  • Mistake: Using the wrong operator for the intended operation.

    • Tip: Double-check the operator you are using to ensure it matches the operation you want to perform.

  • Mistake: Forgetting to initialize variables before using them in expressions.

    • Tip: Always initialize your variables to avoid unexpected results.

  • Mistake: Misunderstanding operator precedence.

    • Tip: Use parentheses to explicitly define the order of operations in complex expressions.

Conclusion

In this section, we covered the various types of operators and how to use them in expressions. We also provided practical examples and exercises to reinforce your understanding. Mastering these concepts is essential for performing calculations, making decisions, and manipulating data in your RPG programs. In the next section, we will explore control structures, which will allow you to control the flow of your programs based on conditions and loops.

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