IF Statements: Making Decisions in Code

IF statements are fundamental control flow structures in programming. They allow your program to execute different blocks of code based on whether a specific condition is true or false.

The Basic IF Structure

The simplest form of an IF statement checks a condition. If the condition evaluates to true, the code inside the IF block is executed.

Syntax (Conceptual)

IF condition THEN -- Code to execute if condition is TRUE END IF

Most programming languages use a similar structure, often with parentheses around the condition and curly braces or indentation to define the code block.

Example in Pseudocode:

SET temperature = 25 IF temperature > 20 THEN PRINT "It's a warm day!" END IF

In this example, since 25 is indeed greater than 20, the message "It's a warm day!" will be displayed.

IF-ELSE Statements

What if you want to do something else when the condition is false? That's where the ELSE clause comes in. An IF-ELSE statement provides an alternative block of code to execute when the IF condition is not met.

Syntax (Conceptual)

IF condition THEN -- Code to execute if condition is TRUE ELSE -- Code to execute if condition is FALSE END IF

Example in Pseudocode:

SET age = 15 IF age >= 18 THEN PRINT "You are an adult." ELSE PRINT "You are a minor." END IF

Here, because 15 is not greater than or equal to 18, the ELSE block will be executed, printing "You are a minor."

IF-ELSE IF-ELSE Statements

You can chain multiple conditions using ELSE IF (or ELIF in some languages). This allows for more complex decision-making with multiple possibilities.

Syntax (Conceptual)

IF condition1 THEN -- Code for condition1 ELSE IF condition2 THEN -- Code for condition2 ELSE IF condition3 THEN -- Code for condition3 ELSE -- Code if none of the above conditions are met END IF

Example in Pseudocode:

SET score = 75 IF score >= 90 THEN PRINT "Grade: A" ELSE IF score >= 80 THEN PRINT "Grade: B" ELSE IF score >= 70 THEN PRINT "Grade: C" ELSE PRINT "Grade: D or F" END IF

With a score of 75, the program will check the conditions in order. It's not >= 90, not >= 80, but it IS >= 70, so it prints "Grade: C".

Interactive Example

Enter a number to see how IF-ELSE IF statements work:

Common Operators in Conditions

Conditions typically involve comparison operators:

You can also use logical operators to combine conditions: