Question

In the following program, number the marked statements to show the order in which they will execute (the logical order of execution). Also, what is the output if the input is 10? #include using namespace std; int secret(int, int); void func(int x, int& y); int main() { int num1, num2; num1 = 6; cout << "Enter a positive integer: "; cin >> num2; cout << endl; cout << secret(num1, num2) << endl; num2 = num2 - num1; cout << num1 << " " << num2 << endl; func(num2, num1); cout << num1 << " " << num2 << endl; return 0; } int secret(int a, int b) { int d; d = a + b; b = a * d; return b; } void func (int x, int& y) { int val1, val2; val1 = x + y; val2 = x * y; y = val1 + val2; cout << val1 << " " << val2 << endl; }

Short answer

Output is: 96, 6 4, 10 24, 34 4.

Step-by-step solution

Determine Order of Program Execution

The order of execution is crucial to understand the program flow. The statements will execute in the following order, assuming the input is provided correctly: 1. `num1 = 6;` 2. `cout << "Enter a positive integer: ";` 3. `cin >> num2;` 4. `cout << endl;` 5. `cout << secret(num1, num2) << endl;` 6. The function `secret(int a, int b)` is called, executing: - `d = a + b;` - `b = a * d;` - `return b;` 7. `num2 = num2 - num1;` 8. `cout << num1 << " " << num2 << endl;` 9. `func(num2, num1);` 10. In the function `func(int x, int& y)`, executing: - `val1 = x + y;` - `val2 = x * y;` - `y = val1 + val2;` - `cout << val1 << " " << val2 << endl;` 11. `cout << num1 << " " << num2 << endl;` 12. `return 0;`

Analyze the Function 'secret'

The `secret` function is called with parameters `a = num1 = 6` and `b = num2 = 10`. Inside the function: - `d = a + b = 6 + 10 = 16;` - `b = a * d = 6 * 16 = 96;` The function returns `b`, which is 96. This value is printed by `cout`.

Update and Output Variables After 'secret' Execution

After the `secret` function executes, `num2` is updated: - `num2 = num2 (10) - num1 (6) = 4` The program prints: `cout << num1 << " " << num2 << endl;`, which outputs `6 4`.

Analyze the Function 'func'

The `func` function is called with `x = num2 = 4` and `y = num1 = 6` (using reference, y will modify num1): - `val1 = x + y = 4 + 6 = 10` - `val2 = x * y = 4 * 6 = 24` - `y = val1 + val2 = 10 + 24 = 34` This affects `num1`, setting it to 34. The function prints: `10 24`.

Final Output After 'func' Execution

Finally, the main function prints the modified `num1` and `num2` values: - `cout << num1 << " " << num2 << endl;` Outputs `34 4`, since `num1` was changed to 34 and `num2` remains 4.

Key concepts

Order of Execution

Understanding the order of execution in a C++ program is key to predicting its behavior. Programs execute from top to bottom, except when functions change this flow. In our exercise, the main function starts the sequence. Here's how it works:

• First, `num1` is set to 6.
• Then, the program prompts the user for input, storing it in `num2`.
• It proceeds by calling the `secret` function.
• After returning, it adjusts `num2`, outputs intermediate results, and finally calls the `func` function.
• After finishing with `func`, it outputs the final results.

This step-by-step order ensures that each line executes logically, utilizing any required input or earlier results.

Pass by Reference

In C++, functions can receive arguments by value or by reference. Understanding this concept helps in controlling how data is modified inside functions. In pass-by-reference, functions work on actual variables instead of copies, allowing changes to persist beyond function scope.
This concept is applied in the `func` function of our problem. The parameter `y` uses pass-by-reference, indicated by the `&` symbol. When `func` modifies `y`, it updates `num1` in the `main` program, not a separate copy.

• Original `num1` value affects calculations directly.
• Changes in `func` reflect in `num1` outside `func`.

Such modifications are powerful but require careful control to avoid unintended side-effects.

Function Parameters

Function parameters in C++ are an essential part of how functions work. They allow functions to receive input data, which they can process and return results. This feature also ensures reusability and flexibility of code.
In our exercise:

• `secret` and `func` both have parameters, which dictate their operations.
• `secret` receives `num1` and `num2`, process these values, and returns a result.
• `func` is called with `num2` and a reference to `num1` as arguments.

These parameters help customize what the function does each time it is called, adapting to different values or scenarios.

Console Input and Output

Console I/O (Input/Output) is how C++ programs communicate with users. This interaction allows users to input data during program execution and view outputs.
In our exercise, the `cin` command collects input from the user, while `cout` is used multiple times to display different results.

• At the beginning, `cout` prompts for an integer input, and `cin` reads this input into `num2`.
• Subsequent `cout` calls display results of computations, including outputs of function calls.

Using `cin` and `cout` effectively makes the program interactive and informative, enhancing user engagement and understanding.