Why operators are needed in C++ - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add two integers and print the result.

C++

#include <iostream>
int main() {
    int a = 5, b = 3;
    int sum = a [1] b;
    std::cout << sum << std::endl;
    return 0;
}

Drag options to blanks, or click blank then click option'

A-

B+

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction - instead of addition.

Using multiplication * or division / by mistake.

The + operator adds two numbers. Here, it adds a and b to get the sum.

2fill in blank

medium

Complete the code to compare if two numbers are equal.

C++

#include <iostream>
int main() {
    int x = 10, y = 10;
    if (x [1] y) {
        std::cout << "Equal" << std::endl;
    } else {
        std::cout << "Not equal" << std::endl;
    }
    return 0;
}

Drag options to blanks, or click blank then click option'

A==

B<

C>

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using assignment = instead of comparison ==.

Using inequality != by mistake.

The == operator checks if two values are equal. It returns true if they are the same.

3fill in blank

hard

Fix the error in the code to multiply two numbers correctly.

C++

#include <iostream>
int main() {
    int a = 4, b = 5;
    int product = a [1] b;
    std::cout << product << std::endl;
    return 0;
}

Drag options to blanks, or click blank then click option'

A-

B+

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition + or subtraction - instead of multiplication.

Using division / by mistake.

The * operator multiplies two numbers. Using it here calculates the product of a and b.

4fill in blank

hard

Fill both blanks to create a dictionary-like structure using a map and check if a key exists.

C++

#include <iostream>
#include <string>
#include <map>
int main() {
    std::map<std::string, int> scores;
    scores["Alice"] = 90;
    if (scores.[1]("Alice") [2] scores.end()) {
        std::cout << "Alice's score is " << scores["Alice"] << std::endl;
    }
    return 0;
}

Drag options to blanks, or click blank then click option'

Afind

B==

C!=

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using count method incorrectly here.

Using equality == instead of not equal !=.

The find method searches for a key in the map. If the result is not equal (!=) to end(), the key exists.

5fill in blank

hard

Fill all three blanks to create a conditional expression that checks if a number is positive, negative, or zero.

C++

#include <iostream>
#include <string>
int main() {
    int num = -5;
    std::string result = (num [1] 0) ? "Positive" : ((num [2] 0) ? "Negative" : (num [3] 0 ? "Zero" : "Error"));
    std::cout << result << std::endl;
    return 0;
}

Drag options to blanks, or click blank then click option'

A>

B<

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up greater than and less than operators.

Using not equal != instead of equal == for zero check.

The first blank uses > to check if num is positive. The second uses < to check if negative. The third uses == to check if zero.

Practice

1. Why do we need operators like + and - in C++?

easy

A. To perform calculations like addition and subtraction

B. To write comments in the code

C. To define new functions

D. To create variables

Solution

1. Step 1: Understand the role of operators

   Operators like + and - are symbols that perform mathematical operations.

2. Step 2: Identify what these operators do

   The + operator adds numbers, and - subtracts numbers, enabling calculations in code.

3. Final Answer:

   To perform calculations like addition and subtraction -> Option A

4. Quick Check:

   Operators do math = To perform calculations like addition and subtraction [OK]

Hint: Operators do math and comparisons in code [OK]

Common Mistakes:

• Thinking operators create variables
• Confusing operators with comments
• Believing operators define functions

2. Which of the following is the correct way to use the multiplication operator in C++?

easy

A. int result = 5 * 3;

B. int result = 5 + 3;

C. int result = 5 . 3;

D. int result = 5 x 3;

Solution

1. Step 1: Recall the multiplication operator symbol

   In C++, the multiplication operator is *, not x or ..

2. Step 2: Check the syntax of each option

   int result = 5 * 3; uses * correctly between two numbers, making it valid syntax.

3. Final Answer:

   int result = 5 * 3; -> Option A

4. Quick Check:

   Multiplication uses * symbol = int result = 5 * 3; [OK]

Hint: Use * for multiplication, not x or dot [OK]

Common Mistakes:

• Using 'x' instead of '*' for multiplication
• Using '.' as operator
• Confusing addition '+' with multiplication

3. What is the output of this C++ code?

int a = 10;
int b = 3;
int c = a % b;
std::cout << c;

medium

A. Syntax error

B. 3

C. 0

D. 1

Solution

1. Step 1: Understand the modulus operator

   The % operator gives the remainder of division. Here, 10 divided by 3 leaves remainder 1.

2. Step 2: Calculate the remainder

   10 % 3 = 1, so c is assigned 1, which is printed.

3. Final Answer:

   1 -> Option D

4. Quick Check:

   10 % 3 = 1 [OK]

Hint: Modulus % gives remainder after division [OK]

Common Mistakes:

• Confusing % with division
• Expecting quotient instead of remainder
• Thinking output is syntax error

4. Identify the error in this C++ code snippet:

int x = 5;
int y = 10;
int z = x + y - ;
std::cout << z;

medium

A. Wrong use of semicolon

B. Missing operand after '-' operator

C. Incorrect variable declaration

D. No error, code runs fine

Solution

1. Step 1: Check the expression after assignment

   The expression x + y - ; ends with a minus operator but no number or variable after it.

2. Step 2: Understand operator requirements

   Operators like - need two operands. Missing the second operand causes a syntax error.

3. Final Answer:

   Missing operand after '-' operator -> Option B

4. Quick Check:

   Operator needs two values = Missing operand after '-' operator [OK]

Hint: Operators need two values; check for missing operands [OK]

Common Mistakes:

• Ignoring missing operand errors
• Thinking semicolon causes error
• Assuming variable declaration is wrong

5. You want to check if a number n is even or odd in C++. Which operator helps you do this efficiently?

hard

A. The multiplication operator *

B. The addition operator +

C. The modulus operator %

D. The assignment operator =

Solution

1. Step 1: Understand the problem of checking even or odd

   A number is even if it divides by 2 with zero remainder, odd otherwise.

2. Step 2: Identify the operator that gives remainder

   The modulus operator % returns the remainder after division, so n % 2 tells if n is even or odd.

3. Final Answer:

   The modulus operator % -> Option C

4. Quick Check:

   Use % 2 to check even/odd = The modulus operator % [OK]

Hint: Use % 2 to test even or odd numbers quickly [OK]

Common Mistakes:

• Using + or * instead of %
• Confusing assignment with comparison
• Not understanding remainder concept