Conditions & Branching

Conditions let programs choose

A condition is a yes-or-no question the program can answer.

If the answer is yes, run one set of instructions. Otherwise, run another. It is the programming version of: IF it is raining, take an umbrella. OTHERWISE, leave it at home.

Write the decision in plain logic

This program checks an age and selects one of two messages.

CREATE age AS 20

IF age GREATER OR EQUAL TO 18 THEN
    SHOW "Adult"
OTHERWISE
    SHOW "Minor"
END IF

The same idea in Python

Python uses if and else, with indentation showing which statements belong to each branch.

age = 20

if age >= 18:
    print("Adult")
else:
    print("Minor")

The same idea in JavaScript

JavaScript places the condition in parentheses and branch instructions inside braces.

const age = 20;

if (age >= 18) {
    console.log("Adult");
} else {
    console.log("Minor");
}

The same idea in C#

C# expresses the same decision with if and else.

int age = 20;

if (age >= 18)
{
    Console.WriteLine("Adult");
}
else
{
    Console.WriteLine("Minor");
}

The same idea in Java

Java is nearly identical to C# for this simple decision.

int age = 20;

if (age >= 18) {
    System.out.println("Adult");
} else {
    System.out.println("Minor");
}

The same idea in C++

C++ again uses the same underlying branch structure.

int age = 20;

if (age >= 18)
{
    std::cout << "Adult\n";
}
else
{
    std::cout << "Minor\n";
}