Why functions are needed in C++ - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of code using functions for reuse

What is the output of this C++ code that uses a function to add two numbers?

C++

#include <iostream>
using namespace std;

int add(int a, int b) {
    return a + b;
}

int main() {
    cout << add(3, 4) << endl;
    cout << add(10, 20) << endl;
    return 0;
}

A 7\n30

B 34\n1020

C 7 30

D Compilation error

💡 Hint

Look at what the add function returns and how cout prints it.

The function add returns the sum of two integers. The main function calls add twice and prints the results on separate lines.

🧠 Conceptual

intermediate

Why use functions in programming?

Which of the following is the main reason programmers use functions?

A To make the program run faster by skipping code

B To make the program use more memory

C To repeat the same code many times without rewriting it

D To confuse other programmers

💡 Hint

Think about how functions help avoid writing the same code again and again.

Functions allow programmers to write a piece of code once and reuse it multiple times, making programs shorter and easier to maintain.

❓ Predict Output

advanced

Output of code demonstrating function parameters and scope

What is the output of this C++ program that uses a function to modify a local variable?

C++

#include <iostream>
using namespace std;

void changeValue(int x) {
    x = 100;
}

int main() {
    int a = 10;
    changeValue(a);
    cout << a << endl;
    return 0;
}

A 0

B 100

C Compilation error

D 10

💡 Hint

Remember that function parameters are passed by value by default in C++.

The function changeValue changes its local copy of x, but does not affect the variable a in main, so a remains 10.

❓ Predict Output

advanced

Output of code using function to avoid repetition

What will this C++ program print when run?

C++

#include <iostream>
using namespace std;

void printHello() {
    cout << "Hello!" << endl;
}

int main() {
    printHello();
    printHello();
    printHello();
    return 0;
}

A Hello!\nHello!\nHello!

B Hello! Hello! Hello!

C Hello!\nHello!\nHello!\nHello!

D Compilation error

💡 Hint

Each call to printHello prints one line with Hello!

The function printHello prints "Hello!" followed by a newline. It is called three times, so three lines are printed.

🧠 Conceptual

expert

Why functions improve program structure

Which statement best explains how functions improve the structure of a program?

A Functions increase the size of the program to make it more complex

B Functions break a program into smaller parts, making it easier to understand and fix

C Functions make programs run faster by skipping unnecessary code

D Functions prevent the program from running if there is an error

💡 Hint

Think about how dividing work into smaller pieces helps with understanding.

Functions divide a program into smaller, manageable pieces. This makes the program easier to read, test, and fix.