Question

(Checkerboard Pattern of Asterisks) Write a program that displays the following checkerboard pattern. Your program must use only three output statements, one of each of the following forms: cout << "* "; cout << ' '; cout << endl;

Short answer

Implement a nested loop structure with 8 iterations each. Use an if-else condition to alternate between printing '* ' and ' ' based on the current indices. Output endl after each line to form the checkerboard pattern.

Step-by-step solution

Understanding the Checkerboard Pattern

A checkerboard pattern consists of alternating squares of two different colors. In a typical 8x8 checkerboard pattern, the squares alternate between black and white. To represent this pattern with asterisks, we will print an asterisk (*) for a black square and a space for a white square. Each line of the pattern will have eight elements, and the pattern will have eight lines.

Creating the Outer Loop for Rows

To create the 8x8 checkerboard pattern, we will need to print eight lines of output. This requires an outer loop that will iterate eight times, once for each line. We can use a for loop that starts at 0 and iterates until it is less than 8, incrementing the loop counter by 1 each time.

Creating the Inner Loop for Columns

Inside the outer loop, we need an inner loop to handle the printing of '*' and spaces in each line. The inner loop will also iterate eight times, and within this loop, we will determine whether to print an asterisk or a space based on the current column and row numbers. If the sum of the row and column index is even, print '*', otherwise print a space.

Implementing the Checkerboard Logic

In each iteration of the inner loop, use an if-else statement to check if the sum of the current row index and column index is even. If it is, output '* '; otherwise, output ' '. After the inner loop finishes, output a newline character using 'cout << endl;' to move to the next line of the pattern.

Writing the Main Function

Write the main function and declare it with 'int main()'. Inside, implement the outer and inner loops as described in the previous steps. Ensure to include the proper headers and use the correct syntax for C++ output.

Key concepts

C++ Loops

Loops in C++ are powerful control structures that allow you to repeat a block of code multiple times. They are fundamental in creating patterns, such as the checkerboard discussed in this exercise. There are different types of loops in C++, including 'for', 'while', and 'do-while'. For our checkerboard pattern, we utilize the 'for' loop because we know exactly how many times we want to execute the loop: eight times for the eight rows of the checkerboard pattern.

Here's a basic syntax of a 'for' loop in C++:

for (initialization; condition; update) {
// Code to execute repeatedly
}

In creating our checkerboard pattern, we use two nested 'for' loops. The outer loop runs to create the rows, while the inner loop is used for the columns within each row. The use of nested loops is essential when you want to work with multidimensional data or patterns like our 8x8 checkerboard.

C++ Conditional Statements

Conditional statements in C++, such as 'if' and 'else' are used to perform different actions based on different conditions. They are indispensable when it comes to decision-making in a program. In the context of creating a checkerboard pattern, we use an 'if-else' statement to decide whether to print an asterisk or a space character.

The condition we check is whether the sum of the current row and column index is even. In C++, the modulus operator '%' is used to determine if a number is even or odd by checking the remainder of the division by 2. Here's the general structure:

if (condition) {
// Code to execute if the condition is true
} else {
// Code to execute if the condition is false
}

When applied, the 'if' block in our checkerboard program prints an asterisk for even sums, while the 'else' block prints a space for odd sums. Conditional statements are what make the pattern appear by selectively printing characters based on the position within the loop.

C++ Output

Output in C++ is typically done using the 'cout' stream, which is included in the 'iostream' library. 'cout' is utilized to display information to the user. In the checkerboard pattern exercise, we are given the constraint of using only three output statements: one to print an asterisk followed by a space, another to print a space character, and the last to print a newline character.

To adhere to these constraints, we smartly use the 'cout' statement in strategic places. After determining whether to print an asterisk or a space within the 'if-else' conditional structure, we print them using 'cout'. The 'endl' is used after the inner loop to move to the next line, ensuring our pattern forms correctly on separate lines.

Understanding how to manage output in C++ is crucial because it determines how the user will interact with and understand your program. Correctly structuring the output lets the user see the desired checkerboard pattern, providing visual feedback that the program works as intended.