main function and program entry in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this C++ program?

Consider the following C++ program. What will it print when run?

C++

#include <iostream>

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

A Hello World

B hello, world!

C Compilation error

D Hello, World!

💡 Hint

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

The program prints exactly "Hello, World!" followed by a newline. The capitalization and punctuation must match exactly.

❓ Predict Output

intermediate

What is the output of this program with command line arguments?

What will this C++ program print if run with the command line: ./program apple banana?

C++

#include <iostream>

int main(int argc, char* argv[]) {
    std::cout << argc << std::endl;
    std::cout << argv[1] << std::endl;
    return 0;
}

A

3
apple

B

2
apple

C

2
banana

D

3
banana

💡 Hint

Remember the first argument is the program name itself.

argc counts the program name plus arguments, so argc is 3. argv[1] is the first argument after the program name, which is "apple".

❓ Predict Output

advanced

What is the output of this program with multiple return statements?

What will this C++ program print when run?

C++

#include <iostream>

int main() {
    std::cout << "Start" << std::endl;
    return 1;
    std::cout << "End" << std::endl;
}

A End

B

Start
End

C Start

D Compilation error

💡 Hint

Code after return is not executed.

The program prints "Start" then returns 1 immediately. The line printing "End" is never reached.

❓ Predict Output

advanced

What error does this program produce?

What error will this C++ program cause when compiled?

C++

#include <iostream>

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

A No error, prints Hello

B Error: main must return int

C Error: missing semicolon

D Error: std::cout not declared

💡 Hint

Check the return type of main function in C++.

In standard C++, main must return int. Using void main() causes a compilation error.

🧠 Conceptual

expert

What is the value of 'result' after running this program?

Consider this C++ program. What is the value of the variable 'result' after main finishes?

C++

#include <iostream>

int main() {
    int result = 0;
    try {
        throw 5;
        result = 1;
    } catch (int e) {
        result = e;
    }
    return result;
}

A 5

B 0

C 1

D Compilation error

💡 Hint

Look at what happens when an exception is thrown and caught.

The throw 5 causes control to jump to the catch block, setting result to 5. The assignment result=1 is skipped.