Question

What is the output of the following code? int num = 12; while (num >= 0) { if (num % 5 == 0) break; cout << num << " "; num = num - 2; } cout << endl;

Short answer

The output is "12 ". The loop breaks when `num` becomes 10.

Step-by-step solution

Understand the Code Structure

The given code is a `while` loop that continues as long as the variable `num` is greater than or equal to 0. Within the loop, there's an `if` condition that checks if `num` is divisible by 5, and if true, it breaks out of the loop. Otherwise, it prints the current value of `num` and decreases `num` by 2.

Initial Variables Setup

The variable `num` is initialized to 12. The loop will begin its execution by assessing the `while` condition, which is true since 12 is greater than or equal to 0.

First Iteration

In the first iteration, the code checks the `if` condition `num % 5 == 0`, which checks if `num` is divisible by 5. Since 12 is not divisible by 5, it proceeds to print `num`, which is 12, followed by a space. Then, `num` is decremented by 2, making it 10.

Second Iteration

With `num` now being 10, the loop begins again. The condition `num % 5 == 0` is true because 10 is divisible by 5. Hence, the `break` statement is executed, and the loop is terminated. Nothing more is printed, and the `cout << endl;` statement is executed, which only moves the cursor to a new line.

Key concepts

while loop

When coding in C++, the `while loop` is an essential control structure used to repeat a block of code as long as a specified condition remains true. In simple terms, it tests a condition before executing the loop's code block. If the condition evaluates to true, the code block runs; if false, the loop terminates.

The basic syntax for a `while loop` in C++ is: ```cpp while (condition) { // code to be executed } ``` In our example, the loop checks if `num` is greater than or equal to 0. This means the loop continues to execute as long as `num` is at least 0.

It's crucial to ensure that the condition will eventually become false. Otherwise, we might encounter an infinite loop, where the code executes endlessly. This can crash programs or devices, so proper use of loops is fundamental.

conditional statements

Conditional statements, like `if-else`, are building blocks in C++ that allow decision-making in code execution. They enable the program to choose different execution paths based on specified conditions.

The `if` statement evaluates a condition inside parentheses. If true, the code block under the `if` statement is executed. If not, the code block is skipped. Here is how it works: ```cpp if (condition) { // execute if condition is true } ``` In our example, the `if` statement checks whether `num % 5 == 0`. This checks if `num` is divisible by 5 without leaving a remainder.

Understanding conditional statements is key to programming logic because they determine how a program makes decisions and reacts to different inputs.

break statement

The `break` statement is used in C++ to exit a loop prematurely, halting its execution before the condition naturally turns false. It becomes handy when we want to stop loop execution once a specific condition is met.

In the provided code, the `break` statement occurs within an `if` conditional. If `num` is divisible by 5, the `break` halts the loop regardless of the `while` condition. This efficient control mechanism prevents unnecessary iterations, optimizing program performance.

Using `break` statements responsibly is essential in managing loops. Without them, programs might conduct unneeded computations or accidentally generate infinite loops, making them inefficient or even non-functional.

programming logic

Program logic refers to the systematic approach used to solve a problem in programming, where control structures such as loops and conditionals play a vital role. Understanding programming logic involves recognizing patterns and systematically breaking down tasks into an ordered sequence of operations.

In our sample problem, the logic shifts from initializing variables to creating conditions that control the flow of the loop. Specifically, `while` and `if` determine the program's decision-making process. Logic involves:

• Identifying what checks need to be made
• Understanding possible outcomes
• Efficiently managing loop exits upon meeting conditions

Developing solid programming logic is foundational for writing clear, efficient, and bug-free code, making it easier to troubleshoot and refine any program.