Question

Given that the following code is correctly inserted into a program, state its entire output as to content and form. (Assume all variables are properly declared.) num = 0; for (i = 1; i <= 4; i++) { num = num + 10 * (i - 1); cout << num << " "; } cout << endl;

Short answer

0 10 30 60

Step-by-step solution

Understand the Code Loop

The given code has a `for` loop that iterates from 1 to 4. Within each iteration, the variable `num` is updated based on the formula `num = num + 10 * (i - 1)`. After updating `num`, it is printed followed by a space.

Analyze Each Iteration

Let's analyze what happens during each iteration of the for loop: - **Iteration 1 (i = 1):** - Calculate: `num = num + 10 * (1 - 1) = 0 + 10 * 0 = 0` - Output: `0 ` - **Iteration 2 (i = 2):** - Calculate: `num = num + 10 * (2 - 1) = 0 + 10 * 1 = 10` - Output: `10 ` - **Iteration 3 (i = 3):** - Calculate: `num = num + 10 * (3 - 1) = 10 + 10 * 2 = 30` - Output: `30 ` - **Iteration 4 (i = 4):** - Calculate: `num = num + 10 * (4 - 1) = 30 + 10 * 3 = 60` - Output: `60 `

Final Output With Line Break

After the loop completes all its iterations, a newline character is printed. The final output will therefore be composed of the numbers separated by spaces and ending with a newline.

Key concepts

For Loop in C++

A `for loop` is a crucial component in C++ programming, allowing you to execute a block of code multiple times. The loop runs based on a specified condition. In the given exercise, the loop starts with `i = 1` and continues until `i <= 4` is no longer true.
The structure of a `for loop` consists of three parts:

• Initialization: Sets the starting point of the loop, here it is `i = 1`.
• Condition: Determines when the loop will end. In this exercise, the loop ends when `i` exceeds 4.
• Iteration Expression: Modifies the loop variable, here it is `i++`, which increments `i` by one in each iteration.

These components help control the loop execution efficiently. The `for loop` is especially useful when you know in advance how many times a block of code should run, as demonstrated in the code.

Variable Initialization

Variable initialization is the process of assigning a starting value to a variable when it is created. In C++, it is a critical step before using variables in your program.
In the example provided, `num` is initialized to 0. This step ensures that the variable `num` has a known initial value before it enters the loop and participates in calculations.
Initialization prevents garbage values or unintended results, making sure the code behaves as expected. This practice contributes to reliable and predictable code execution. Especially in loops, having initialized variables can prevent logical errors from occurring.

Output Formatting

Proper `output formatting` is essential in making sure your output is human-readable and understandable. In C++, various operators and functions are available to aid in formatting outputs.
In the given exercise, the `cout` function is used to print the variable `num` followed by a space. Each iteration concatenates its output to the sequence `0 10 30 60`, each separated by a space. The program ends with printing a newline character using `cout << endl;`, which neatly closes the output sequence and moves the cursor to the next line.
Formatting is crucial for both debugging and presenting results. Well-formatted output ensures clarity and readability, making it easier to see results at a glance.

Increment Operation

In programming, an `increment operation` is a fundamental arithmetic operation that increases the value of a variable by a fixed amount. In C++, the `++` operator is used to increment an integer variable by one.
In the exercise, the loop variable `i` is incremented in each pass through the loop using the `i++` syntax. This action continues until the loop condition `i <= 4` is false. Incrementing by one allows the loop to proceed smoothly through its iterations without manual intervention.
The `increment operation` helps in traversing through data structures or simply controlling the flow of loops, providing a concise way to manage iteration within the loops.