Question

include using namespace std; void func1(); void func2(); int main() { int num; cout << "Enter 1 or 2: "; cin >> … # What is the output of the following program? #include using namespace std; void func1(); void func2(); int main() { int num; cout << "Enter 1 or 2: "; cin >> num; cout << endl; cout << "Take "; if (num == 1) func1(); else if (num == 2) func2(); else cout << "Invalid input. You must enter a 1 or 2" << endl; return 0; } void func1() { cout << "Programming I." <

Short answer

a. "Take Programming I."; b. "Take Programming II."; c. "Invalid input. You must enter a 1 or 2"; d. "Invalid input. You must enter a 1 or 2".

Step-by-step solution

Understanding the Program Structure

The program starts by including the iostream library and uses the standard namespace. It declares two functions, `func1` and `func2`, which are defined later. The `main` function prompts the user to enter a value (1 or 2), reads this input, and then either calls `func1`, `func2`, or prints an invalid input message.

Analyzing Input Case 1

If the user inputs `1`, the program will execute the branch where `if (num == 1)` is true. It first prints "Take " and then calls `func1`. The `func1` function outputs "Programming I." Therefore, the output will be: "Take Programming I.".

Analyzing Input Case 2

If the user inputs `2`, the elseif branch `else if (num == 2)` is executed. The program will print "Take " and then call `func2`. The `func2` function outputs "Programming II." Hence, the complete output will be: "Take Programming II.".

Analyzing Input Case 3

If the user inputs `3`, neither `if (num == 1)` nor `else if (num == 2)` is satisfied. The program will proceed to the `else` clause, which outputs: "Invalid input. You must enter a 1 or 2".

Analyzing Negative Input Case -1

If the user inputs `-1`, just like with the input `3`, neither the `if` nor the `else if` conditions hold true. The `else` part is executed, resulting in the output: "Invalid input. You must enter a 1 or 2".

Key concepts

Control Structures in C++

Control structures are fundamental in directing the flow of a C++ program. In this scenario, we encounter an `if-else` control structure, which decides which parts of the code to execute based on a condition. The program asks the user to enter either `1` or `2`. Depending on the input:

• If the input is `1`, the program executes a specific block of code.
• If the input is `2`, a different block is executed.
• If neither, an error message is displayed.

The `if-else` statement allows handling multiple program paths based on different conditions.
This capability is vital for creating dynamic programs that respond to various inputs.

Function Calling and Execution

Functions are reusable blocks of code that perform specific tasks. They help in organizing code and make it reusable and easier to maintain. In the provided program, we have two functions:

• `func1`: Outputs "Programming I." when called.
• `func2`: Outputs "Programming II." when called.

The `main` function controls the program flow and based on user input, it calls either `func1` or `func2`. Function calls allow us to execute pre-defined code which can be run multiple times throughout a program.
This modular approach is efficient and helps in keeping the code clean and organized.

Input and Output in C++

Input and output (I/O) are crucial for interacting with users. In C++, I/O is commonly managed using streams from the iostream library. In this program:

• `cout` is used to display text to the user. For instance, it asks the user to "Enter 1 or 2:" and outputs responses based on conditions.
• `cin` is used to receive input from the user. Here, it captures the number entered by the user and stores it in the variable `num`.

Understanding I/O operations is essential for creating interactive programs where user data can influence program behavior.

Conditional Statements in C++

Conditional statements are used to perform different actions based on different conditions. In our program, conditional lines utilize the `if`, `else if`, and `else` keywords.

The `if` statement checks if the user's input is `1`. If true, it calls `func1`.

The `else if` statement checks if the input is `2`. If true, it calls `func2`.

The `else` statement catches any other input, ensuring that a meaningful message "Invalid input. You must enter a 1 or 2" is displayed for improper entries.

These conditional checks ensure the program can respond appropriately to a variety of user inputs.