Conditional logic (if-then decisions) in Intro to Computing - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is conditional logic in computing?

Conditional logic is a way for a computer to make decisions by checking if something is true or false, then doing different actions based on that.

beginner

Explain the if-then structure in simple terms.

It means: if a condition is true, then do something. If not, skip it or do something else.

beginner

What happens when the condition in an if-statement is false?

If the condition is false, the computer skips the 'then' part and moves on to the next instructions or checks other conditions.

beginner

How is an if-then decision like choosing what to wear based on weather?

Just like you decide to wear a raincoat if it is raining, a computer uses if-then to choose actions based on conditions it checks.

beginner

What is the role of an else in conditional logic?

Else tells the computer what to do if the 'if' condition is not true. It is like a backup plan.

What does an if-statement check?

A How to store data

B If a condition is true or false

C What color to display on screen

D How many times to repeat an action

An if-statement checks whether a condition is true or false to decide what to do next.

What happens if the condition in an if-statement is false and there is no else?

A The computer does nothing for that if-statement and moves on

B The computer repeats the if-statement

C The computer crashes

D The computer always runs the then-part

If the condition is false and no else is given, the computer skips the then-part and continues.

Which real-life example best matches an if-then decision?

A If it rains, then take an umbrella

B Always eat breakfast

C Count how many steps you take

D Write a letter

Deciding to take an umbrella only if it rains is like an if-then decision.

What does the else part do in an if-else statement?

A Runs before the if condition

B Runs only if the if condition is true

C Runs when the if condition is false

D Stops the program

Else runs when the if condition is false, providing an alternative action.

Which symbol is commonly used to start an if-statement in many programming languages?

A switch

B for

C while

D if

The keyword 'if' is used to start an if-statement.

Describe how an if-then decision works using a simple real-life example.

Think about a daily choice you make based on a yes/no question.

Explain the difference between if and else in conditional logic.

Consider what happens when the condition is true versus false.

Practice

1.

What does an if statement do in a program?

easy

A. It stores data in a list.

B. It repeats code multiple times.

C. It checks a condition and runs code only if the condition is true.

D. It creates a new variable.

Solution

1. Step 1: Understand the purpose of if

   An if statement asks a question that can be true or false.

2. Step 2: Identify what happens when the condition is true

   If the condition is true, the program runs the code inside the if block; otherwise, it skips it.

3. Final Answer:

   It checks a condition and runs code only if the condition is true. -> Option C

4. Quick Check:

   if = condition check [OK]

Hint: Remember: if means 'only if true' run code [OK]

Common Mistakes:

• Thinking if repeats code like a loop
• Confusing if with data storage
• Believing if creates variables

2.

Which of the following is the correct syntax for an if statement in Python?

___ x > 10:
    print("x is greater than 10")

easy

A. else

B. for

C. while

D. if

Solution

1. Step 1: Identify the keyword for condition checking

   Python uses if to start a condition check.

2. Step 2: Match the syntax with the code block

   The colon : after the condition is required to start the indented block.

3. Final Answer:

   if -> Option D

4. Quick Check:

   Python if syntax = if [OK]

Hint: If checking condition, start with 'if' keyword [OK]

Common Mistakes:

• Using 'for' or 'while' instead of 'if'
• Forgetting the colon after the condition
• Using 'else' without an 'if'

3.

What will be printed by this Python code?

age = 20
if age >= 18:
    print("Adult")
else:
    print("Child")

medium

A. Adult

B. No output

C. Child

D. Error

Solution

1. Step 1: Check the condition age >= 18

   Variable age is 20, which is greater than or equal to 18, so condition is true.

2. Step 2: Determine which block runs

   Since condition is true, the print("Adult") line runs, printing "Adult".

3. Final Answer:

   Adult -> Option A

4. Quick Check:

   20 >= 18 = Adult [OK]

Hint: Check if condition is true to pick printed output [OK]

Common Mistakes:

• Choosing 'Child' without checking condition
• Thinking no output if condition true
• Assuming syntax error

4.

Find the error in this code snippet:

if score > 50
    print("Pass")
else:
    print("Fail")

medium

A. Wrong indentation of print statements

B. Missing colon after if condition

C. Using else without if

D. Incorrect comparison operator

Solution

1. Step 1: Check syntax of if statement

   Python requires a colon : at the end of the if condition line.

2. Step 2: Identify the missing colon

   The line if score > 50 is missing the colon, causing a syntax error.

3. Final Answer:

   Missing colon after if condition -> Option B

4. Quick Check:

   Colon needed after if condition [OK]

Hint: Look for missing colon after if condition line [OK]

Common Mistakes:

• Ignoring missing colon error
• Thinking indentation is wrong here
• Confusing else usage

5.

You want to write a program that prints "Good morning" if the hour is less than 12, and "Good afternoon" otherwise. Which code correctly implements this?

hour = 10
___ hour < 12:
    print("Good morning")
else:
    print("Good afternoon")

hard

A. if

B. else if

C. elif

D. while

Solution

1. Step 1: Choose the correct keyword for the first condition

   The first condition must start with if to check if hour < 12.

2. Step 2: Use else for the alternative

   The else block runs if the if condition is false, printing "Good afternoon".

3. Final Answer:

   if -> Option A

4. Quick Check:

   Use if for first condition, else for alternative [OK]

Hint: Start conditions with if, alternatives with else [OK]

Common Mistakes:

• Using 'else if' instead of 'if' in Python
• Using 'elif' without a preceding if
• Using 'while' instead of if for decisions