If then, else statements

 

If-then-else statements are fundamental conditional statements in programming. They are decision-making tools that allow a program to execute different blocks of code based on whether a specific condition is true or false.

Think of it as giving your program instructions for a choice:

If this one thing is true, then do this action, else (otherwise) do this other action.

🧠 A Simple Analogy

Imagine you're getting dressed in the morning:

• IF it is raining,

• THEN I will take an umbrella.

• ELSE I will wear sunglasses.

Your program will only choose one of those actions (take an umbrella OR wear sunglasses), never both. The decision is based entirely on the condition: "Is it raining?"

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## How It's Structured in Code

While the exact syntax (the words and symbols) changes between programming languages, the logic is always the same. It's often broken down into three parts:

1. if (The Condition)

   • This is the "question" or the "test." It must be something that can be evaluated as either true or false.

   • Example: if (age >= 18)

2. then (The "True" Block)

   • This is the code that runs only if the condition is true. (In many modern languages, the word then is implied and not actually typed).

   • Example: print("You are eligible to vote.")

3. else (The "False" Block)

   • This is the optional code that runs only if the condition is false.

   • Example: print("You are not eligible to vote yet.")

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## Examples in Pseudocode

Pseudocode is a way of writing out code logic in plain English.

Example 1: Basic if-else

Here, we check a test score.

score = 75

if (score > 60) then
    print("You passed!")
else
    print("You failed.")

Result: Because 75 is greater than 60 (the condition is true), the program will print: "You passed!"

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Example 2: Chaining with else if

You can also check multiple conditions in a row using else if (or elif in languages like Python). The program checks them in order and stops as soon as it finds one that is true.

temperature = 22

if (temperature > 30) then
    print("It's hot outside.")
else if (temperature > 15) then
    print("It's nice and warm.")
else
    print("It's cold.")

Result:

1. Is 22 > 30? False. It skips the first block.

2. else if... Is 22 > 15? True. It runs this block.

3. The program prints: "It's nice and warm."

4. It skips the final else block because it already found a true condition.

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## Key Points to Remember

• Only One Path: In an if-else chain, only one block of code will ever be executed.

• else is Optional: You can have an if statement all by itself. If the condition is false, the program just skips that block and moves on.

• Core Building Block: This simple structure is one of the most important concepts in programming, forming the basis for complex logic and decision-making.