Question

include #include #include using namespace std; int main() { int x, y; string message; double z;… # What is the output of the following program? #include #include #include using namespace std; int main() { int x, y; string message; double z; x = 4; y = 3; z = 2.5; cout << static_cast(pow(x, 2.0)) << endl; cout << static_cast(pow(z, y)) << endl; cout << pow(x, z) << endl; cout << sqrt(36.0) << endl; z = pow(9.0, 2.5); cout << z << endl; message = "Using C++ predefined function"; cout << "Length of message = " << message.length() << endl; return 0; }

Short answer

The output is: 16, 15, 32, 6, 243, and "Length of message = 28".

Step-by-step solution

Initialization of Variables

The program begins by including necessary libraries for input-output operations, mathematical computations, and string handling. Then it declares variables: integers `x` and `y`, a string `message`, and a double `z`. The variables are initialized as follows: `x = 4`, `y = 3`, `z = 2.5`.

First Output - Calculate x^2

The line `cout << static_cast(pow(x, 2.0)) << endl;` calculates the power of `x` raised to `2` using the `pow` function. Since `x` is `4`, it computes `4^2 = 16` and casts the result to an integer, which remains `16`. This value is printed as the first output.

Second Output - Calculate z raised to y

In the line `cout << static_cast(pow(z, y)) << endl;`, the program calculates `z` raised to the power of `y`. Here, `z = 2.5` and `y = 3`, so it computes `2.5^3 = 15.625`. This result is cast to an integer, resulting in `15`, which is printed as the second output.

Third Output - Calculate x raised to z

The program calculates `x` raised to `z` with `cout << pow(x, z) << endl;`. For `x = 4` and `z = 2.5`, it computes `4^2.5 ≈ 32`. The result is printed as `32` as this line outputs the floating-point result without casting to an integer.

Fourth Output - Square Root of 36

Using `cout << sqrt(36.0) << endl;`, the program computes the square root of `36`. The result is `6.0`, as `6 * 6 = 36`, and this value is printed in floating-point format.

Fifth Output - Set z and Output

The line `z = pow(9.0, 2.5);` calculates `9` raised to the power of `2.5`, yielding approximately `243.0`. This value is assigned to `z`, and `cout << z << endl;` outputs `243`.

Sixth Output - Length of Message String

Finally, `message` is assigned the value "Using C++ predefined function". The program prints `Length of message = ` followed by `message.length()` which is `28`, since the string "Using C++ predefined function" contains `28` characters including spaces.

Key concepts

C++ Variables

In C++, variables are used to store data that can be accessed and manipulated by the program. Variables have specific data types like `int` for integers, `double` for floating-point numbers, and `string` for text sequences. The original program declares and initializes variables such as `x` and `y` as integers, `z` as a double, and `message` as a string.

Variables are declared by specifying the data type followed by the variable name. For example, `int x;` declares an integer variable `x`. Once declared, variables must be initialized before use, like `x = 4;` assigns the value `4` to `x`. Proper variable initialization is crucial because using a variable before giving it a value can lead to unpredictable results.
It is a good programming practice to choose meaningful variable names to make the code readable and maintainable.

C++ Functions

Functions in C++ are used to perform specific tasks and can be predefined in libraries or user-defined. A function takes inputs, performs a task, and often returns a result. Common predefined functions in C++ include `cout` for output and `cin` for input.

Functions are declared with a return type (like `int`, `void`), followed by the function name and parentheses `()`. Inside the parentheses, function parameters are defined if necessary. In the exercise, C++'s math functions `pow` and `sqrt` are used for calculations. These are part of the `` library, indicating they are not standalone but part of the C++ standard library.
Using functions helps in making the code modular and reusable. It breaks the task into smaller parts and simplifies debugging, as a problem might be isolated to a specific function.

Pow Function

The `pow` function in C++ is used to compute powers. It is part of the `` library and is used to raise a number to a specific power, which can be either an integer or a floating-point number.

The syntax of the `pow` function is simple: `pow(base, exponent)`. In the program, `pow(x, 2.0)` calculates the square of `x`. Another line `pow(z, y)` calculates `z` to the power of `y`. This function returns a double value by default, reflecting the continuous nature of exponents, which can result in decimal outputs.
Keep in mind that the base and the exponent can be of any numeric type, but the function always returns a double, due to the mathematical operations that often result in non-integer numbers.

Sqrt Function

The `sqrt` function provides a simple way to compute the square root of a number in C++. Like `pow`, it is included in the `` library.

Its usage is straightforward: `sqrt(value)`, where `value` is the number whose square root is sought. In the problem's solution, `sqrt(36.0)` calculates the square root of `36`, resulting in `6`. This function returns a double, even if the square root is an integer, to maintain type consistency in mathematical operations.
Using the `sqrt` function is efficient and a preferred way to deal with square roots in C++, ensuring precision and simplicity in code.

String Handling in C++

Handling strings in C++ involves using the `` library, which provides a variety of functions to manipulate text.

In the exercise, the `string message` is used, and `message.length()` computes the number of characters in the string, including spaces. This result is `28`, demonstrating basic string manipulation. The `length()` function returns the size of the string as an integer. In C++, strings can be concatenated using the `+` operator, can be accessed via indices, and possess robust methods for string handling compared to character arrays.
Proper understanding of string handling is crucial in programming, especially for software that heavily deals with text data.