Else–if ladder in C++ - Mini Project: Build & Apply

Else-if ladder

📖 Scenario: You are creating a simple program that categorizes a person's age group based on their age. This is useful in many real-life situations like assigning age-appropriate activities or content.

🎯 Goal: Build a C++ program that uses an else-if ladder to print the correct age group for a given age.

📋 What You'll Learn

Create an integer variable called age with the value 25

Create an integer variable called ageGroup to store the category code

Use an else-if ladder to assign ageGroup based on age: 1 for child (0-12), 2 for teenager (13-19), 3 for adult (20-59), 4 for senior (60+)

Print the ageGroup variable

💡 Why This Matters

🌍 Real World

Age group classification is used in schools, healthcare, marketing, and entertainment to provide age-appropriate services and content.

💼 Career

Understanding conditional statements like else-if ladders is fundamental for software developers to control program flow based on different conditions.

1

Create the age variable

Create an integer variable called age and set it to 25.

C++

int age = 25;  // Your code here

Hint

Use int to declare an integer variable named age and assign it the value 25.

2

Create the ageGroup variable

Create an integer variable called ageGroup and initialize it to 0.

C++

int age = 25;
int ageGroup = 0;  // Your code here

Hint

Declare ageGroup as an integer and set it to zero to start.

3

Use an else-if ladder to assign ageGroup

Write an if-else if ladder to assign ageGroup based on age: set ageGroup = 1 if age is between 0 and 12 inclusive, ageGroup = 2 if between 13 and 19 inclusive, ageGroup = 3 if between 20 and 59 inclusive, and ageGroup = 4 if 60 or above.

C++

int age = 25;
int ageGroup = 0;
// Your code here

Hint

Use multiple else if statements to check the age ranges and assign the correct ageGroup value.

4

Print the ageGroup

Write a std::cout statement to print the value of ageGroup.

C++

int age = 25;
int ageGroup = 0;

if (age >= 0 && age = 13 && age = 20 && age = 60) {
    ageGroup = 4;
}

// Your code here

Hint

Use std::cout << ageGroup << std::endl; to print the value of ageGroup.

Practice

1.

What does an else-if ladder do in C++?

easy

A. Skips all conditions and runs the else block always

B. Runs all conditions regardless of their truth

C. Only runs the last condition in the ladder

D. Checks multiple conditions one by one and runs the first true block

Solution

1. Step 1: Understand the purpose of else-if ladder

   An else-if ladder is used to check multiple conditions in order, one after another.

2. Step 2: Identify how conditions are evaluated

   It runs the code block for the first condition that is true and skips the rest.

3. Final Answer:

   Checks multiple conditions one by one and runs the first true block -> Option D

4. Quick Check:

   Else-if ladder = first true condition runs [OK]

Hint: Remember: else-if stops at first true condition [OK]

Common Mistakes:

• Thinking all conditions run
• Believing else always runs
• Confusing else-if with separate ifs

2.

Which of the following is the correct syntax for an else-if ladder in C++?

int x = 10;
if (x < 5) {
  // code A
} _____ (x < 15) {
  // code B
} else {
  // code C
}

easy

A. else if

B. elseif

C. else_if

D. else if()

Solution

1. Step 1: Recall correct else-if syntax in C++

   The correct keyword is else if with a space, no underscores or parentheses after else.

2. Step 2: Check each option

   Options A, B, and C are invalid syntax in C++.

3. Final Answer:

   else if -> Option A

4. Quick Check:

   Correct syntax = else if [OK]

Hint: Use 'else if' with space, no underscores or parentheses [OK]

Common Mistakes:

• Writing 'elseif' as one word
• Using underscores like 'else_if'
• Adding parentheses after else

3.

What will be the output of this C++ code?

int num = 7;
if (num > 10) {
  std::cout << "Greater than 10";
} else if (num > 5) {
  std::cout << "Greater than 5";
} else {
  std::cout << "5 or less";
}

medium

A. Greater than 5

B. 5 or less

C. Greater than 10

D. No output

Solution

1. Step 1: Evaluate first condition (num > 10)

   7 is not greater than 10, so this block is skipped.

2. Step 2: Evaluate second condition (num > 5)

   7 is greater than 5, so this block runs and prints "Greater than 5".

3. Final Answer:

   Greater than 5 -> Option A

4. Quick Check:

   7 > 5 = true, prints "Greater than 5" [OK]

Hint: Check conditions top to bottom, first true runs [OK]

Common Mistakes:

• Choosing first condition output incorrectly
• Ignoring else-if order
• Assuming else runs always

4.

Find the error in this else-if ladder code snippet:

int score = 85;
if (score >= 90) {
  std::cout << "Grade A";
} else if score >= 80 {
  std::cout << "Grade B";
} else {
  std::cout << "Grade C";
}

medium

A. Missing semicolon after std::cout

B. Missing parentheses around condition in else-if

C. Incorrect use of else instead of else-if

D. Using >= instead of >

Solution

1. Step 1: Check syntax of else-if condition

   In C++, conditions must be inside parentheses. The else-if line lacks parentheses.

2. Step 2: Verify other parts

   Semicolons and operators are correct; only parentheses are missing.

3. Final Answer:

   Missing parentheses around condition in else-if -> Option B

4. Quick Check:

   Conditions need parentheses [OK]

Hint: Always put conditions inside parentheses [OK]

Common Mistakes:

• Forgetting parentheses in if/else-if
• Missing semicolons after statements
• Confusing else and else-if syntax

5.

Write an else-if ladder to print the day of the week given an integer day (1 to 7). What will be printed if day = 5?

int day = 5;
if (day == 1) {
  std::cout << "Monday";
} else if (day == 2) {
  std::cout << "Tuesday";
} else if (day == 3) {
  std::cout << "Wednesday";
} else if (day == 4) {
  std::cout << "Thursday";
} else if (day == 5) {
  std::cout << "Friday";
} else if (day == 6) {
  std::cout << "Saturday";
} else if (day == 7) {
  std::cout << "Sunday";
} else {
  std::cout << "Invalid day";
}

hard

A. Thursday

B. Saturday

C. Friday

D. Invalid day

Solution

1. Step 1: Match the value of day with conditions

   day is 5, so the else-if condition day == 5 is true.

2. Step 2: Identify the output for day == 5

   The code prints "Friday" for day 5.

3. Final Answer:

   Friday -> Option C

4. Quick Check:

   day 5 = Friday [OK]

Hint: Match day number to correct else-if condition [OK]

Common Mistakes:

• Mixing up day numbers and names
• Forgetting else block for invalid days
• Using wrong comparison operators