What is C++ - Practice Questions & Exercises

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of simple C++ program with variables

What is the output of this C++ program?

C++

#include <iostream>
int main() {
    int a = 5;
    int b = 3;
    std::cout << "Sum: " << a + b << std::endl;
    return 0;
}

A Sum: 8

B Sum: 53

C Sum: 15

D Sum: 2

💡 Hint

Remember that + adds numbers, not strings.

The program adds integers 5 and 3, resulting in 8.

🧠 Conceptual

intermediate

What is the main purpose of C++?

Which option best describes the main purpose of C++?

A A language for system programming and performance-critical applications

B A language mainly for web page styling

C A language only for database queries

D A language used exclusively for mobile app design

💡 Hint

Think about where speed and control over hardware matter.

C++ is widely used for system software, games, and applications needing high performance.

❓ Predict Output

advanced

Output of C++ code with pointers

What is the output of this C++ program?

C++

#include <iostream>
int main() {
    int x = 10;
    int* p = &x;
    *p = 20;
    std::cout << x << std::endl;
    return 0;
}

A 10

B Compilation error

C 20

D Address of x

💡 Hint

Changing value via pointer changes original variable.

Pointer p points to x, so *p = 20 changes x to 20.

🔧 Debug

advanced

Identify the error in this C++ code

What error does this C++ code produce?

C++

#include <iostream>
int main() {
    int a = 5;
    int b = 0;
    std::cout << a / b << std::endl;
    return 0;
}

A No error, outputs 0

B Syntax error: missing semicolon

C Type error: incompatible types

D Division by zero runtime error

💡 Hint

Dividing by zero is not allowed.

Dividing an integer by zero causes a runtime error or crash.

🚀 Application

expert

What is the output of this C++ code using classes?

What is the output of this program?

C++

#include <iostream>
class Counter {
public:
    int count = 0;
    void increment() { count++; }
};
int main() {
    Counter c1, c2;
    c1.increment();
    c2.increment();
    c2.increment();
    std::cout << c1.count << " " << c2.count << std::endl;
    return 0;
}

A 2 1

B 1 2

C 0 0

D Compilation error

💡 Hint

Each object has its own count variable.

c1 increments once, c2 increments twice, so output is '1 2'.

Practice

1. What is C++ primarily used for?

easy

A. Managing databases only

B. Designing websites

C. Creating fast and efficient programs

D. Writing poetry

Solution

1. Step 1: Understand C++ purpose

   C++ is a programming language designed for speed and efficiency.

2. Step 2: Compare options

   Only Creating fast and efficient programs matches the main use of C++ for fast and efficient programs.

3. Final Answer:

   Creating fast and efficient programs -> Option C

4. Quick Check:

   C++ use = Creating fast and efficient programs [OK]

Hint: Remember C++ is for fast programs, not just websites [OK]

Common Mistakes:

• Confusing C++ with web design languages
• Thinking C++ is only for databases
• Assuming C++ is for creative writing

2. Which of the following is the correct way to start a C++ program?

easy

A. int main() {}

B. void start() {}

C. begin() {}

D. function main() {}

Solution

1. Step 1: Identify C++ program entry point

   C++ programs start execution from the main function.

2. Step 2: Check syntax correctness

   Only int main() {} is valid C++ syntax for program start.

3. Final Answer:

   int main() {} -> Option A

4. Quick Check:

   Program start = int main() {} [OK]

Hint: Look for int main() as the program start [OK]

Common Mistakes:

• Using void instead of int for main
• Using non-C++ keywords like function or begin
• Missing return type in main function

3. What will the following C++ code output?

int main() {
  int x = 5;
  int y = 3;
  int z = x + y;
  std::cout << z;
  return 0;
}

medium

A. 53

B. Error

C. 0

D. 8

Solution

1. Step 1: Calculate the sum of x and y

   x is 5 and y is 3, so z = 5 + 3 = 8.

2. Step 2: Understand output statement

   std::cout << z; prints the value of z, which is 8.

3. Final Answer:

   8 -> Option D

4. Quick Check:

   5 + 3 = 8 [OK]

Hint: Add numbers before output to find result [OK]

Common Mistakes:

• Concatenating numbers as strings
• Expecting syntax error due to missing headers
• Confusing variable names

4. Find the error in this C++ code:

int main() {
  int number = 10
  std::cout << number;
  return 0;
}

medium

A. Wrong variable type

B. Missing semicolon after variable declaration

C. Missing return statement

D. Incorrect output syntax

Solution

1. Step 1: Check variable declaration line

   The line int number = 10 is missing a semicolon at the end.

2. Step 2: Verify other lines

   Other lines are correct: output and return statements are fine.

3. Final Answer:

   Missing semicolon after variable declaration -> Option B

4. Quick Check:

   Semicolon missing = syntax error [OK]

Hint: Look for missing semicolons after statements [OK]

Common Mistakes:

• Ignoring missing semicolon errors
• Assuming return statement is missing
• Thinking output syntax is wrong

5. You want to write a C++ program that prints "Hello, C++!" to the screen. Which code snippet correctly does this?

hard

A. int main() { std::cout << "Hello, C++!"; return 0; }

B. void main() { print("Hello, C++!"); }

C. main() { cout << Hello, C++!; }

D. int start() { std::cout << "Hello, C++!"; }

Solution

1. Step 1: Check function signature

   Only int main() is the correct entry point for C++ programs.

2. Step 2: Verify output syntax

   std::cout << "Hello, C++!"; correctly prints the message.

3. Step 3: Confirm return statement

   Return 0 indicates successful program end.

4. Final Answer:

   int main() { std::cout << "Hello, C++!"; return 0; } -> Option A

5. Quick Check:

   Correct main and output syntax = int main() { std::cout << "Hello, C++!"; return 0; } [OK]

Hint: Use int main() and std::cout for output [OK]

Common Mistakes:

• Using void main() instead of int main()
• Missing quotes around string
• Using undefined print function