Question

include using namespace std; int main() { int x, y, z; x = 4; y = 5; z = y + 6; while(((z - x) % 4) != 0) { cout… # What is the output of the following program? #include using namespace std; int main() { int x, y, z; x = 4; y = 5; z = y + 6; while(((z - x) % 4) != 0) { cout << z << " "; z = z + 7; } cout << endl; return 0; }

Short answer

The output is: `11 18 25 `

Step-by-step solution

Initialize Variables

Three integer variables are declared: `x`, `y`, and `z`. The values are set to `x = 4`, `y = 5`, and `z` is calculated as `z = y + 6`, which means `z` becomes 11.

Understand the While Loop Condition

The `while` loop continues to execute as long as the condition `((z - x) % 4) != 0` is true. This means it continues if the remainder of `(z - x)` divided by `4` is not zero.

Evaluate Initial Condition

Initially, `z = 11` and `x = 4`, so `z - x = 7`. The remainder of `7 / 4` is `3`, which is not zero. The loop condition is satisfied, so the body of the loop will execute.

Loop Execution and Modification of z

Inside the loop, `cout << z << " "` prints the current value of `z`. Then, `z = z + 7` increases the value of `z` by 7. The loop repeats as long as the condition is true.

Iteration Details

- Start: `z = 11`; `(11 - 4) % 4 = 3`, print `11`. - Next: `z = 18`; `(18 - 4) % 4 = 2`, print `18`. - Next: `z = 25`; `(25 - 4) % 4 = 1`, print `25`. - Next: `z = 32`; `(32 - 4) % 4 = 0`, condition becomes false.

End of Loop and Program Conclusion

When `z = 32`, the condition becomes false, terminating the loop. The program then prints a newline with `cout << endl;` and returns `0`, ending the program.

Key concepts

Problem Solving

Problem-solving in C++ often involves breaking down complex tasks into manageable steps. Let's take the given program as an example. To predict output, you need to understand the sequence of operations. This involves:

• Understanding how variables interact with each other.
• Determining how loops affect the flow of the program.
• Recognizing patterns and predicting the end condition of loops.

By examining how each line of code contributes to the overall purpose, you can clarify each part's role and assess the effect it has on the program's outcome.

Loops in C++

Loops in C++ allow sections of code to be executed repeatedly under certain conditions. In our example, a `while` loop repeatedly executes its code block as long as the condition evaluates to true. The syntax of the `while` loop is quite straightforward: ```cpp while(condition) { // code block to be executed } ``` In our program, the loop evaluates `((z - x) % 4) != 0`. This means the loop will continue until the difference between `z` and `x` is a multiple of 4. With each iteration, `z` is increased by 7, pushing the program towards the loop's termination.

Output Prediction

Predicting output is a critical skill in programming and can often be done by simulating the code. Look at how variables change over iterations to foresee the end result. In our example, the `cout << z` command within the loop belongs at predicting values:

• First iteration prints `z = 11`.
• Next it prints `z = 18` as `z` increases by 7.
• Following iterations produce `z = 25`, and finally,
• when `z` becomes `32`, the condition fails and loop exits.

Understanding how variables update through iterations is key for making accurate predictions about what will be displayed.

C++ Syntax

Understanding C++ syntax is fundamental to writing correct programs. Let’s break down some key parts: - **Include Directive:** `#include ` tells the compiler to include the standard input-output library. - **Namespace Declaration:** `using namespace std;` allows access to standard functions like `cout` without prefixing `std::`. - **Variable Declaration and Initialization:** Variables are declared with `int x, y, z;` and initialized within the program. - **Main Function:** Every C++ program must have a `main`, which serves as the entry point for the execution. - **Loop Control Structure:** Use of `while` for iteration. - **Output Statements:** `cout` prints output to the screen. Familiarity with these basics ensures clarity on how each piece connects to functionally create the program’s behavior.