Conditional Statements (if, else if, else, switch)

3.3.1 Conditional Statements (if, else if, else, switch)

Imagine you're at a crossroads, and you need to decide which way to go. Your decision depends on a condition, like "If the sign says 'Beach', go left. Otherwise, go straight."

Conditional Statements are programming instructions that allow your program to make decisions based on whether a certain condition is true or false. They let your code choose different paths of execution.

Here are the main types of conditional statements:

• if statement:
  • This is the simplest decision-maker. It says: "IF a condition is true, THEN do this specific action."
  • If the condition is false, the action is skipped.

Example:

IF (it is raining) THEN

   Take an umbrella.

In code:

weather = "raining"

if weather == "raining":

   print("Take an umbrella.")

• if-else statement:
  • This gives your program two options. It says: "IF a condition is true, THEN do this action. ELSE (otherwise), do that different action."
  • Only one of the two actions will ever happen.

Example:

IF (you are hungry) THEN

   Eat a snack.

ELSE

   Go play outside.

In code:

is_hungry = True

if is_hungry:

   print("Eat a snack.")

else:

   print("Go play outside.")

• if-else if-else (or elif in Python) statement:
  • This allows your program to check multiple conditions in order. It says: "IF condition 1 is true, do this. ELSE IF condition 2 is true, do that. ELSE (if none of the above are true), do something else."
  • The computer checks each condition one by one. As soon as it finds a true condition, it performs that action and then skips all the other else if and else parts.

Example:

IF (grade is A) THEN

   You get a gold star!

ELSE IF (grade is B) THEN

   You get a silver star!

ELSE

   Keep trying!

In code (Python example):

grade = "B"

if grade == "A":

   print("You get a gold star!")

elif grade == "B": # Only checked if grade is NOT "A"

   print("You get a silver star!")

else: # Only runs if grade is NOT "A" and NOT "B"

   print("Keep trying!")

• switch statement (in languages like Java, C++, C#):
  • This is a special type of conditional statement used when you have many possible exact values for a single variable, and you want to do different things for each value.
  • It's like having a menu: "Choose option 1 for pizza, option 2 for pasta, option 3 for salad."
  • It's often cleaner than a long chain of if-else if statements when checking for exact matches.

Example (Java concept):

// Imagine 'dayOfWeek' is a number from 1 (Monday) to 7 (Sunday)

switch (dayOfWeek) {

   case 1:

       System.out.println("It's Monday!");

       break; // Stop here

   case 5:

       System.out.println("It's Friday!");

       break;

   default: // If dayOfWeek is none of the above

       System.out.println("It's a weekday or weekend.");

}

• (Note: Python does not have a direct switch statement, but uses if-elif-else or dictionaries for similar logic.)

Conditional statements are essential for making programs smart and able to respond differently to different situations.

Bibliography:

• W3Schools - Python If...Else: https://www.w3schools.com/python/python_conditions.asp
• GeeksforGeeks - Conditional Statements in C/C++: https://www.geeksforgeeks.org/cpp/decision-making-c-cpp/
• Wikipedia - Conditional (computer programming):

https://en.wikipedia.org/wiki/Conditional_(computer_programming))