Structure of a C++ program - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple C++ program with main function

What is the output of this C++ program?

C++

#include <iostream>

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

A Hello C++!

B Hello, C++!

C hello, C++!

D Compilation error

💡 Hint

Look carefully at the exact text inside the quotes and the capitalization.

The program prints exactly "Hello, C++!" followed by a newline. The std::endl inserts a newline and flushes the output.

❓ Predict Output

intermediate

Value of variable after execution

What is the value of variable x after running this program?

C++

#include <iostream>

int main() {
    int x = 5;
    x = x + 10;
    std::cout << x << std::endl;
    return 0;
}

A 15

B 10

C 5

D Compilation error

💡 Hint

Look at how x is updated after initialization.

x starts at 5, then 10 is added, so x becomes 15.

❓ Predict Output

advanced

Output of program with missing return in main

What is the output or result of this C++ program?

C++

#include <iostream>

int main() {
    std::cout << "Test";
}

A Test

B Compilation error: missing return statement

C No output

D Runtime error

💡 Hint

In modern C++, main can omit return 0; and still run correctly.

Since C++11, main returns 0 implicitly if no return statement is present. The program prints "Test".

❓ Predict Output

advanced

Output of program with multiple functions

What is the output of this C++ program?

C++

#include <iostream>

void greet() {
    std::cout << "Hi";
}

int main() {
    greet();
    std::cout << " there!" << std::endl;
    return 0;
}

A Compilation error

B

Hi there

C

Hi there!

D !ereht iH

💡 Hint

Check the exact characters printed and the effect of std::endl.

The greet function prints "Hi" without newline. main prints " there!" and then std::endl adds a newline. So output is "Hi there!\n".

🧠 Conceptual

expert

Order of sections in a C++ program

Which of the following shows the correct order of sections in a typical C++ program?

A 1, 3, 2, 4

B 3, 1, 2, 4

C 2, 1, 3, 4

D 1, 2, 3, 4

💡 Hint

Think about what the compiler needs first to understand the program.

First, #include directives bring in libraries. Then namespace declarations set scope. Then functions are declared/defined. Finally, main function runs the program.