Question

Write C++ statements to do the following. a. Declare int variable num1 and num2. b. Prompt the user to input two numbers. c. Input the first number in num1 and the second number in num2. d. Output num1, num2, and 2 times num1 minus num2. Your output must identify each number and the expression.

Short answer

Declare variables, prompt input, read values, compute, and output results.

Step-by-step solution

Declare Variables

Declare two integer variables named 'num1' and 'num2'. This is done with the C++ syntax for declaring integer variables. ```cpp int num1, num2; ```

Prompt for Input

Print a message to the screen asking the user to enter two numbers. This helps the user understand what is expected. ```cpp std::cout << "Please enter two numbers: "; ```

Read User Input

Read the two numbers entered by the user from the input stream and store them in 'num1' and 'num2'. Use the 'cin' object for this purpose. ```cpp std::cin >> num1 >> num2; ```

Calculate Expression

Calculate the expression '2 times num1 minus num2'. This will be used to show the result. No explicit storing is needed, as it can be calculated directly when displaying the output.

Output Results

Output the values of 'num1', 'num2', and the result of the expression (2 * num1 - num2) with descriptive text. ```cpp std::cout << "num1: " << num1 << ", num2: " << num2; std::cout << ", 2*num1 - num2: " << 2 * num1 - num2 << std::endl; ```

Key concepts

Variable Declaration

In C++ programming, declaring variables is a fundamental task. A variable is like a box in memory where we can store data. Variables must be declared before they can be used, which lets the program know to reserve space in memory.

To declare a variable, we use a specific type. Common types include integers, floating-point numbers, and characters. For example:

• To declare an integer variable (whole numbers) like 'num1' and 'num2', you write: int num1, num2;

This statement tells the compiler that both 'num1' and 'num2' will hold integer values. Understanding how to declare variables is essential for any C++ program.

User Input

User input allows programs to interact with users by receiving data during execution. In C++, this can be done using the 'cin' object for input operations. This helps to dynamically assign values to variables based on user entries.

To prompt the user for inputs, a common method involves the 'cout' object to display messages: ```cpp std::cout << "Please enter two numbers: "; ``` After that, we use 'cin' to read the provided numbers: ```cpp std::cin >> num1 >> num2; ``` It captures the data entered by the user and stores it in 'num1' and 'num2'. This capability to read input makes programs flexible and user-friendly.

Output Statements

Creating output is crucial for communication in C++ programs, letting us display variables or results. The 'cout' object is used for such tasks. This helps users see what the program has computed or captured as input.

To produce output, combine 'cout' with the insertion operator '<<', like this: ```cpp std::cout << "num1: " << num1 << ", num2: " << num2; ``` Here, we're forming a coherent message to describe which number 'num1' and 'num2' represent. To include mathematical results: ```cpp std::cout << ", 2*num1 - num2: " << 2 * num1 - num2 << std::endl; ``` This statement not only prints variables but also immediate calculations, showing results directly to the user.

Expression Evaluation

Expression evaluation in C++ involves computing or interpreting mathematical expressions defined by operators. This enables us to process data and calculations necessary for programming tasks.

Consider the expression '2 * num1 - num2'. When this expression is evaluated:

• First, the multiplication '2 * num1' is performed.
• Then, the result of '2 * num1' is subtracted by 'num2'.

The evaluated result is then outputted or used in further operations. Knowing how to evaluate expressions allows programmers to derive meaningful outcomes from input data.