If Statements and Selection in Pseudocode

Programs rarely run from start to finish without needing to evaluate data or adjust their execution paths. To build dynamic applications, whether you are validating user input, triggering events in a game, or processing grades, your code needs to make decisions.

In programming, this decision-making process is called Selection. Selection constructs evaluate boolean conditions (statements that resolve to either TRUE or FALSE) and steer the flow of the program accordingly. The most common form of selection is the IF statement.

In this guide, we will explore the core concepts behind IF, ELSE, ELSE IF, and CASE structures. We'll break down the logic with generic examples before explicitly defining the syntax and rules for the AQA, OCR, and Cambridge (CIE) exam boards.

Core Concepts: Making Decisions

At the heart of selection are boolean conditions. The code evaluates an expression (e.g., score > 50). If the evaluation is true, one block of code runs. Let's look at the basic building blocks of selection logic.

The Basic IF Statement

The standalone IF statement executes its nested code block only if the specified condition evaluates to true. If the condition is false, the program entirely skips the block and continues execution underneath.

Adding an ELSE Clause

Often, you want an alternative action to occur if the condition is false. The ELSE keyword acts as a catch-all. It guarantees that if the IF statement fails, the code inside the ELSE block will run instead.

Chaining with ELSE IF

When there are more than two possible outcomes, you can chain conditions together using ELSE IF. The program checks these conditions sequentially from top to bottom. As soon as one evaluates to true, it executes that block and skips the rest.

Using CASE / SWITCH Statements

If you find yourself writing a long chain of ELSE IF statements checking the exact same variable against different specific values, a CASE (or SWITCH) statement provides a much cleaner, more readable structure.

Syntax Variations by Exam Board

While the underlying branching logic remains the same, exam boards require different formatting and structural keywords. Below are the rules and syntax for AQA, OCR, and Cambridge (CIE).

AQA Pseudocode Standard

AQA uses strict capitalization for its control structures. It does not have a dedicated CASE or SWITCH keyword documented in the primary guide, meaning you should rely on nested IF chains instead.

• Keywords: IF, THEN, ELSE IF, ELSE, and ENDIF.
• Operators: Uses standard equality operators like = for checks, not ==.

OCR Pseudocode Standard

OCR syntax generally prefers lowercase conventions. It combines else and if into a single elseif keyword, and utilizes switch for checking multiple fixed states.

• IF Keywords: if/else, elseif, endif. Uses double equals == for comparison.
• SWITCH Keywords: Uses switch, case, default, and endswitch.

Cambridge (CIE / 9618) Standard

The Cambridge International standard is explicit and strict, mirroring legacy languages like Pascal.

• IF Keywords: IF, THEN, ELSE, ENDIF. CIE syntax does not have an explicit ELSE IF keyword; instead, it relies on nesting IF statements inside ELSE blocks or using CASE.
• CASE Keywords: Uses CASE OF, lists the value with a colon, provides a catch-all with OTHERWISE, and closes with ENDCASE.

Conclusion

Selection via IF and CASE statements is what brings programs to life, allowing code to evaluate data and react dynamically. Whether checking age restrictions, processing varying data types, or building complex menus, mastering these control structures is non-negotiable for a programmer.

Remember that while the boolean logic (TRUE/FALSE) evaluating the code branches is universal, your execution depends on your specification. OCR prefers the clean switch, AQA relies entirely on IF/ELSE IF chains, and CIE demands structured CASE OF blocks. Practice these variations in the editor to solidify your understanding.