Question

Suppose that you have the following declarations: int times[30][7]; int speed[15][7]; int trees[100][7]; int students[50][7]; a. Write the definition of the function print that can be used to output the contents of these arrays. b. Write the C++ statements that call the function print to output the contents of the arrays times, speed, trees, and students.

Short answer

Define a `print` function to output 2D arrays and call it with each array, specifying its dimensions.

Step-by-step solution

Understanding the Function Purpose

The task requires writing a function `print` that outputs the contents of arrays with different sizes and then calling this function for each array given. The key point is that this function must handle the printing of arrays with varying numbers of rows.

Writing the Print Function Definition

To output arrays, we define a `print` function that accepts a 2D array and its dimensions as arguments. The function uses nested loops to access and print each element. ``` void print(int array[][7], int num_rows, int num_columns) { for (int i = 0; i < num_rows; i++) { for (int j = 0; j < num_columns; j++) { std::cout << array[i][j] << " "; } std::cout << std::endl; } } ```

Constructing Print Calls for the Arrays

To correctly call the `print` function defined above, you need to specify each array along with its number of rows and columns. Note that all arrays have 7 columns in this scenario. ``` // Assume all needed `#include`s are present int main() { print(times, 30, 7); print(speed, 15, 7); print(trees, 100, 7); print(students, 50, 7); return 0; } ```

Explanation of the Code

The function `print` is designed to handle any 2D array with 7 columns by iterating through each row and column using nested loops, printing each element in sequence. The `main` function demonstrates calls to `print`, where each array is printed by passing its specific number of rows.

Key concepts

2D Arrays

In C++ programming, a 2-dimensional (2D) array is essentially an array of arrays. It is used to store data in a tabular form, with rows and columns. Imagine a spreadsheet; each cell in the spreadsheet is an element in the array.

In the original exercise, we have four 2D arrays declared: `times`, `speed`, `trees`, and `students`. Each of these has a fixed number of columns (7 in this case) but varies in the number of rows. Here's how to envision the arrays:

• `times` has 30 rows.
• `speed` has 15 rows.
• `trees` has 100 rows.
• `students` has 50 rows.

Each element within these arrays can be accessed using two indices: one for the row and another for the column. For instance, to access the element in the first row and second column, you would use `array[0][1]`.

Understanding 2D arrays is crucial when it comes to managing and processing grid-based data effectively in C++.

Function Definition

Defining a function in C++ allows you to reuse code without rewriting it multiple times. Functions are blocks of code designed to perform specific tasks. For the exercise problem, we defined a function named `print`.

This function's purpose is to print the contents of the 2D arrays provided. To define a function to output the arrays, we need to pass:

• The array itself.
• The number of rows (`num_rows`).
• The number of columns (`num_columns`).

Function definitions typically include the return type, the function name, and parameters in parentheses. In our case, `void print(int array[][7], int num_rows, int num_columns)` means:
The function will not return a value (`void`). It accepts a 2D array, the number of rows, and columns, thus offering flexibility in handling arrays with varying row counts.

Learning to define functions effectively is a significant step in writing modular and clean C++ code.

Nested Loops

Nested loops are loops within other loops. They are essential for iterating over elements in multi-dimensional data structures, like 2D arrays.

In the function `print`, we use nested loops to traverse the 2D arrays: an outer loop for rows and an inner loop for columns. The purpose of these loops is to access and print each element in the array.

• The outer loop runs from the first to the last row (`for (int i = 0; i < num_rows; i++)`).
• The inner loop runs through each column in the current row (`for (int j = 0; j < num_columns; j++)`).

This process allows for comprehensive access to each element, ensuring all the array data is processed and printed. Understanding nested loops is fundamental in programming, especially for handling complex data structures like arrays.

They provide an organized method to perform repeated tasks within the structure, making it a powerful tool in C++.

Array Printing

In programming, especially in C++, printing arrays involves displaying the content of the entire array in a readable format. For a 2D array, this means ensuring the output reflects the grid-like structure of the data.

Our `print` function demonstrates how to print a 2D array using standard output in C++:

• Each element is printed with a space between them in a single row.
• An entire row is output before moving to the next line (`std::cout << std::endl`).

This approach maintains the tabular format, making the printout easy to read and understand. Such output methods become critical when debugging or analyzing data, as they offer a clear view of the array contents.

Learning to print arrays correctly aids in both the presentation and interpretation of results, an indispensable skill in C++ programming when working with complex data sets.