Multiple input and output in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to read two integers from input.

C++

#include <iostream>

int main() {
    int a, b;
    std::cin >> [1] >> b;
    std::cout << a + b << std::endl;
    return 0;
}

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

Aa

Bc

Cx

Dnum

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable not declared.

Mixing variable names.

The variable a is declared and should be used to read the first integer input.

2fill in blank

medium

Complete the code to output the product of two integers.

C++

#include <iostream>

int main() {
    int x = 4, y = 5;
    std::cout << x [1] y << 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 instead of multiplication.

Using division or subtraction by mistake.

The multiplication operator * is used to calculate the product of two numbers.

3fill in blank

hard

Fix the error in the code to correctly read three integers and output their sum.

C++

#include <iostream>

int main() {
    int a, b, c;
    std::cin >> a >> b >> [1];
    std::cout << a + b + c << std::endl;
    return 0;
}

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

Ad

Bc

Ce

Dx

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable not declared.

Typo in variable name.

The variable c is declared and should be used to read the third integer input.

4fill in blank

hard

Fill both blanks to read two floats and output their average.

C++

#include <iostream>

int main() {
    float [1], [2];
    std::cin >> a >> b;
    std::cout << (a + b) / 2 << std::endl;
    return 0;
}

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

Aa

Bb

Cx

Dy

Attempts:

3 left

💡 Hint

Common Mistakes

Declaring variables different from those used in input.

Using undeclared variables.

The variables a and b are used to read the two float inputs.

5fill in blank

hard

Fill all three blanks to read three integers and output their maximum.

C++

#include <iostream>
#include <algorithm>

int main() {
    int [1], [2], [3];
    std::cin >> x >> y >> z;
    int max_val = std::max([1], std::max([2], [3]));
    std::cout << max_val << std::endl;
    return 0;
}

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

Ax

By

Cz

Dw

Attempts:

3 left

💡 Hint

Common Mistakes

Using undeclared variables.

Mixing variable names between declaration and usage.

The variables x, y, and z are declared and used to read input and find the maximum.

Practice

1.

Which of the following statements correctly reads two integers a and b from the user in C++?

easy

A. std::cout >> a >> b;

B. std::cin << a << b;

C. std::cout << a << b;

D. std::cin >> a >> b;

Solution

1. Step 1: Understand input operator usage

   In C++, std::cin is used for input and the extraction operator >> reads values.

2. Step 2: Identify correct syntax for multiple inputs

   Using std::cin >> a >> b; reads two integers from the user correctly.

3. Final Answer:

   std::cin >> a >> b; -> Option D

4. Quick Check:

   Input uses std::cin with >> operator [OK]

Hint: Use std::cin with >> to read multiple inputs [OK]

Common Mistakes:

• Using << instead of >> for input
• Using std::cout for input
• Mixing input and output operators

2.

Which of the following lines correctly prints three variables x, y, and z separated by spaces in C++?

easy

A. std::cout << x << ' ' << y << ' ' << z;

B. std::cout << x, y, z;

C. std::cout >> x >> y >> z;

D. std::cin << x << y << z;

Solution

1. Step 1: Understand output operator usage

   In C++, std::cout is used for output and the insertion operator << prints values.

2. Step 2: Print multiple variables with spaces

   Using std::cout << x << ' ' << y << ' ' << z; prints variables separated by spaces correctly.

3. Final Answer:

   std::cout << x << ' ' << y << ' ' << z; -> Option A

4. Quick Check:

   Output uses std::cout with << and spaces [OK]

Hint: Use std::cout with << and spaces to print multiple values [OK]

Common Mistakes:

• Using commas instead of << for output
• Using >> operator for output
• Using std::cin for output

3.

What is the output of the following C++ code if the user inputs 5 10?

int a, b;
std::cin >> a >> b;
std::cout << a + b << ' ' << a * b << std::endl;

medium

A. 15 50

B. 510

C. 5 10

D. Syntax Error

Solution

1. Step 1: Read input values

   The code reads two integers: a = 5 and b = 10 from user input.

2. Step 2: Calculate and print sum and product

   The output prints a + b = 15 and a * b = 50 separated by a space.

3. Final Answer:

   15 50 -> Option A

4. Quick Check:

   Sum and product printed with space [OK]

Hint: Add and multiply inputs, print with space [OK]

Common Mistakes:

• Concatenating numbers as strings
• Forgetting space between outputs
• Confusing input and output operators

4.

Identify the error in the following C++ code snippet:

int x, y;
std::cin << x << y;
std::cout << x << y;

medium

A. Missing semicolon after std::cin

B. >> used instead of << for output

C. << used instead of >> for input

D. Variables x and y not declared

Solution

1. Step 1: Check input operator usage

   Input uses std::cin with extraction operator >>, but code uses << which is wrong.

2. Step 2: Check output operator usage

   The code correctly uses std::cout with insertion operator <<.

3. Final Answer:

   << used instead of >> for input -> Option C

4. Quick Check:

   Input needs >> operator, not << [OK]

Hint: Input uses >>, output uses << operators [OK]

Common Mistakes:

• Swapping << and >> operators
• Confusing std::cin and std::cout
• Ignoring operator direction

5.

Given the following code, what will be the output if the user inputs 3 4 5?

int a, b, c;
std::cin >> a >> b >> c;
std::cout << a + b << ' ' << b + c << ' ' << a + c << std::endl;

medium

A. Runtime Error

B. 7 9 8

C. 3 4 5

D. 12 9 7

Solution

1. Step 1: Read three integers from input

   The variables are assigned as a=3, b=4, c=5 from user input.

2. Step 2: Calculate sums and print

   Prints a + b = 7, b + c = 9, and a + c = 8 separated by spaces.

3. Final Answer:

   7 9 8 -> Option B

4. Quick Check:

   Sum pairs printed correctly [OK]

Hint: Add pairs of inputs and print with spaces [OK]

Common Mistakes:

• Adding all three instead of pairs
• Mixing input order
• Forgetting spaces between outputs