ARRAY

Arrays are like containers that hold multiple values of the same type and stored together under one name.
Instead of creating separate variables like a, b, c, we can declare a single array (e.g., marks[]) that can hold all those values in a structured way.

1] Array :
#include <stdio.h>

int main() {
    int arr[5] = {2, 4, 8, 12, 16};
    
    // Print each element of
    // array using loop
    printf("Printing Array Elements\n"); 
    for(int i = 0; i < 5; i++){
        printf("%d ", arr[i]);
    }
    printf("\n"); 
    
    // Printing array element in reverse
    printf("Printing Array Elements in Reverse\n"); 
    for(int i = 4; i>=0; i--){
        printf("%d ", arr[i]);
    }
    
    return 0;
}


2] Update Array Element:

#include <stdio.h>

int main() {
    int arr[5] = {2, 4, 8, 12, 16};

    // Update the first value
    // of the array
    arr[0] = 1;
    printf("%d", arr[0]);
    return 0;
}


3] Accessing Array Elements:

#include <stdio.h>

int main() {

    // array declaration and initialization
    int arr[5] = {2, 4, 8, 12, 16};

    // accessing element at index 2 i.e 3rd element
    printf("%d ", arr[2]);

    // accessing element at index 4 i.e last element
    printf("%d ", arr[4]);

    // accessing element at index 0 i.e first element
    printf("%d ", arr[0]);
    return 0;
}


4] Size of array :

#include <stdio.h>

int main() {
    int arr[5] = {2, 4, 8, 12, 16};
    
    // Size of the array
    int size = sizeof(arr)/sizeof(arr[0]);
    printf("%d", size);
    return 0;
}


5] Double dimensional array:
// C program to demonstrate working of 2D arrays
#include <stdio.h>

int main() {
    /* 
       Declare and initialize a 2×2 integer array.
       arr[0][0] = 10, arr[0][1] = 20,
       arr[1][0] = 30, arr[1][1] = 40 
    */
    int arr[2][2] = { {10, 20}, {30, 40} };

    printf("2D Array Elements:\n");
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 2; j++) {
            printf("%d ", arr[i][j]);
        }
        printf("\n");
    }

    return 0;
}



#include <stdio.h>

int main() {
  
    // Create and initialize an array with 3 rows
  	// and 2 columns
    int arr[3][2] = { { 0, 1 }, { 2, 3 }, { 4, 5 } };

    // Print each array element's value
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 2; j++) {
            printf("arr[%d][%d]: %d    ", i, j, arr[i][j]);
        }
      	printf("\n");
    }
    return 0;
}