Arrays

Let's dive into arrays in C! Arrays are essential when you want to work with collections of data (like a list of numbers, or names).

What is an Array?

An array is a sequence of elements that are stored in contiguous memory locations. Each element in the array is of the same data type, and you can access them using an index.

Key Points:

• All elements in an array are of the same type (e.g., all integers, all floats).

• The index of an array starts at 0.

• Arrays are fixed in size, meaning you must define the size when you declare the array.

---

Array Declaration and Initialization

To declare an array, you specify the type, the name, and the number of elements (size). You can also initialize the array with values.

Syntax:

type arrayName[arraySize];

Example:

int numbers[5];  // Declares an array 'numbers' that can hold 5 integers

---

Array Initialization

You can initialize an array when you declare it by listing its values in curly braces {}.

Example:

int numbers[5] = {10, 20, 30, 40, 50};  // Array with 5 elements

• The array numbers holds the values 10, 20, 30, 40, 50.

If you don’t initialize all the elements, the remaining elements are automatically set to 0.

Example:

int numbers[5] = {1, 2};  // The first two elements are 1 and 2, rest are 0

---

Accessing Elements in an Array

You can access array elements using their index. Remember, the first element has an index of 0.

Syntax:

arrayName[index];

Example:

int numbers[5] = {10, 20, 30, 40, 50};
printf("%d\n", numbers[0]);  // Outputs 10
printf("%d\n", numbers[4]);  // Outputs 50

---

Modifying Elements

You can change the value of a specific element by assigning it a new value.

Example:

int numbers[5] = {10, 20, 30, 40, 50};
numbers[2] = 100;  // Change the value at index 2 to 100
printf("%d\n", numbers[2]);  // Outputs 100

---

Looping through Arrays

Using loops, especially for loops, is the easiest way to work with arrays.

Example:

int numbers[5] = {10, 20, 30, 40, 50};

for (int i = 0; i < 5; i++) {
    printf("%d\n", numbers[i]);
}

• This loop prints all the elements of the numbers array.

---

Multidimensional Arrays

C allows you to create arrays with more than one dimension. A two-dimensional array can be thought of as a grid or matrix.

Syntax:

type arrayName[rows][columns];

Example:

int matrix[2][3] = {
    {1, 2, 3}, 
    {4, 5, 6}
};

• This creates a 2x3 array (2 rows and 3 columns).

You can access elements of a 2D array like this:

printf("%d\n", matrix[0][1]);  // Outputs 2 (row 0, column 1)

---

Practical Example: Sum of Array Elements

Let’s sum all elements of an integer array.

#include <stdio.h>

int main() {
    int numbers[5] = {10, 20, 30, 40, 50};
    int sum = 0;

    for (int i = 0; i < 5; i++) {
        sum += numbers[i];
    }

    printf("Sum of array elements: %d\n", sum);

    return 0;
}

• This code adds up the elements of the numbers array and prints the sum (150 in this case).

---

Arrays Summary

Concept	Explanation
Array Declaration	type arrayName[size]; - Fixed size, elements stored in sequence.
Indexing	Arrays are indexed starting from 0.
Initialization	Arrays can be initialized when declared (e.g., {1, 2, 3}) or left uninitialized.
Access/Modification	Use arrayName[index] to access or modify elements.
Looping Through Arrays	Use loops to iterate over elements (e.g., for loop).
Multidimensional Arrays	Arrays with more than one dimension (e.g., int matrix[2][3]).

---