Question

(Square of Asterisks) Write a program that reads in the size of the side of a square then prints a hollow square of that size out of asterisks and blanks. Your program should work for squares of all side sizes between 1 and \(20 .\) For example, if your program reads a size of \(5,\) it should print ***** * * * * * * *****

Short answer

Validate the input, print a line of asterisks for the top edge, print lines with asterisks at the beginning and end for the hollow body, and print a line of asterisks for the bottom edge.

Step-by-step solution

Validate Input

Ensure the input is an integer between 1 and 20. If the input is outside this range, ask the user to enter a valid size.

Print the Top Edge of the Square

Print a line with the number of asterisks corresponding to the size of the side of the square.

Print the Hollow Body of the Square

For each line from the second to the second-to-last, print an asterisk, followed by the appropriate number of spaces, and then another asterisk. The number of spaces is the input size minus 2.

Print the Bottom Edge of the Square

Repeat Step 2 to print the bottom edge of the square.

Key concepts

Programming Logic

When approaching a C++ programming challenge, understanding the underlying programming logic is crucial. In the context of creating a hollow square with asterisks, programming logic involves identifying the steps required to achieve the desired output and implementing them in a sequential and logical manner.

For this exercise, the logic consists of four primary steps: input validation, drawing the top edge, constructing the hollow body, and finishing with the bottom edge. Each step corresponds to a specific part of the output. Breaking down a problem into such logical steps simplifies coding and debugging, ensuring that each component functions correctly before moving on to the next. This modularity also aids in maintaining and updating the code in the future.

Input Validation

A vital aspect of any program receiving user input is input validation. This ensures that the program behaves correctly and can handle unexpected or incorrect input gracefully. In our exercise, the size of the square's side must be an integer between 1 and 20.

To implement input validation, one might use a while loop that continues to prompt the user until a valid input is provided. Proper validation not only prevents the program from crashing but also guides the user to enter appropriate data, improving the user experience. Input validation is, therefore, both a guardrail for program integrity and a feature that supports user interaction.

Loop Constructs

C++ includes several loop constructs that allow for repetitive tasks to be completed with ease. The exercise in question takes advantage of loops in multiple steps.

For Loops for Structured Repetition

For instance, when printing the top and bottom edges of the square, a for loop is used to print a row of asterisks equal to the input size. For example, a for loop might look as follows:
for(int i = 0; i < size; i++) { std::cout << '*'; }
This ensures a predictable and structured repetition.

While Loops for Input Validation

Meanwhile, while loops are an excellent choice for input validation, as they can keep prompting until a correct input is received. This adaptability enables loops to handle a broad range of repetitive tasks in programming efficiently.

Conditional Statements

The use of conditional statements enables a program to make decisions based on criteria, allowing for different execution paths. In our C++ exercise, conditional statements are used to determine what to print on each line of the square. For lines that are not the first or last, the program only prints an asterisk at the beginning and end, and spaces in between.

If-Else Construct

An if statement might check whether the current line is the first or last line. If it is, then a row of asterisks is printed; otherwise, the program resorts to an else clause to handle the hollow inside of the square. This ability to course-correct based on conditions is a cornerstone of programming, allowing for dynamic and responsive code based on input and other variables.