Conditionals in Pseudocode

Conditionals allow programs to make decisions based on certain conditions. These decisions determine which blocks of code to execute and which to skip. In pseudocode, two main types of conditionals are commonly used: the IF statement and the CASE OF statement.

In this guide, we'll explore these two types of conditionals in detail, including their variations (with and without ELSE, TO ranges, nested conditionals, etc.).

1. Introduction to Conditionals

Conditionals control the flow of a program by testing conditions (expressions that evaluate to TRUE or FALSE) and executing code based on the results. They allow the program to branch into different directions depending on the data it processes.

Conditionals are crucial for decision-making, and you'll see them in nearly every program that requires logic or interaction.

2. IF Conditional

The IF statement checks whether a condition is TRUE. If it is, the program executes a block of code; otherwise, it skips the block. IF statements can be as simple as a single condition, or as complex as multiple nested conditions with alternatives.

2.1. Simple IF (Without ELSE)

A simple IF statement only checks one condition. If the condition is TRUE, the code inside the IF block runs. If it's FALSE, the program continues without running the block.

Syntax:

• Condition: An expression that evaluates to TRUE or FALSE.
• Statements: Code to execute if the condition is TRUE.

Example:

Here, if the temperature is greater than 30, the program outputs: "It's hot outside!".

2.2. IF with ELSE

An IF...ELSE statement adds an alternative. If the condition is FALSE, the program will execute a second block of code (inside the ELSE part).

Syntax:

Example:

Here, if the age is 18 or greater, the program outputs: "You are an adult." Otherwise, it outputs: "You are a minor."

2.3. Nested IF Statements

You can nest IF statements inside other IF statements to check multiple conditions. This helps when you need to make more complex decisions.

Syntax:

Example:

In this example:

• If the score is 90 or above, the program outputs "Grade: A".
• If the score is exactly 100, it also outputs "Perfect score!".
• If the score is below 90, it checks the nested condition.
• If the score is greater than 80, it outputs "Grade: B"
• If none of the conditions were satisifed, it will finally output "Grade: C or lower"
• Test it out by assigning different values to score variable and see if it works as expected!

3. CASE OF Conditional

The CASE OF statement is useful when you need to test a variable against many possible values. It’s like a more structured version of multiple IF statements and can make the code more readable.

3.1. Simple CASE OF

A CASE OF statement checks the value of a variable and runs code based on which case matches. Each case corresponds to a specific value.

Syntax:

• Identifier: The variable being tested.
• Value: The possible value(s) that the identifier can have.

Example:

In this example, the program checks the value of grade and prints a corresponding message for each grade from A to D.

3.2. CASE OF with OTHERWISE

Sometimes, none of the specific values in a CASE statement match the value of the variable. In such cases, the OTHERWISE clause provides a default action.

Syntax:

Example:

In this example, if the user inputs something other than A, B, C, or D, the program outputs: "Invalid grade."

3.3. CASE OF with Ranges (TO)

The TO keyword allows you to test ranges of values instead of individual values. This is useful for grouping conditions based on ranges, like checking age groups or grades.

Syntax:

Example:

In this example, the program categorizes the user’s age into different life stages based on ranges. The TO keyword allows multiple values to be grouped into one case.

3.4. Nested CASE OF Inside Another Conditional

Just like IF statements, CASE OF conditionals can be nested within other conditionals, such as inside an IF or another CASE OF. This allows for more complex decision-making logic.

Example:

Here, the program first checks if the user is an adult (age 18 or above). If so, it uses a CASE OF statement to determine which region they are from and outputs a customized message.

Conclusion

Conditionals are the backbone of decision-making in programs, allowing them to react dynamically to different inputs and conditions. By understanding the different variations of IF and CASE OF statements, you can write flexible, clean, and efficient pseudocode that handles simple checks as well as complex branching logic.

- IF statements are great for binary decisions or scenarios where you need to check one or two conditions.

- CASE OF statements simplify handling multiple possible values for a variable and improve readability when dealing with many conditions.

Mastering conditionals will significantly enhance your ability to write powerful pseudocode for various scenarios.