Arrays in C

1. Definition

An array is a collection of elements of the same data type stored in contiguous memory locations. Arrays allow you to store and manage multiple values under a single variable name.

2. Syntax

data_type array_name[size];

Explanation:

• data_type: The type of elements in the array (e.g., int, float, char).
• array_name: The name of the array.
• size: The number of elements the array can hold (must be a constant value).

Example:

int numbers[5];

3. Types of Arrays

1. One-Dimensional Arrays

   • A linear collection of elements.

   • Example:

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

2. Two-Dimensional Arrays

   • A table or matrix-like structure with rows and columns.

   • Example:

     int matrix[3][3] = {
         {1, 2, 3},
         {4, 5, 6},
         {7, 8, 9}
     };
     

3. Multi-Dimensional Arrays

   • Arrays with more than two dimensions.

   • Example:

     int tensor[2][3][4];
     

4. Accessing Array Elements

Array elements are accessed using their index, which starts from 0.

Example:

int numbers[5] = {10, 20, 30, 40, 50};
printf("%d", numbers[2]); // Outputs: 30

5. Array Initialization

1. At Declaration:

   int numbers[3] = {10, 20, 30};
   

2. Partially Initialized:

   • Remaining elements are set to 0.

   int numbers[5] = {10, 20}; // Remaining elements: 0, 0, 0
   

3. Uninitialized:

   • Contains garbage values.

   int numbers[5];
   

6. Iterating Through Arrays

Use loops to process all elements in an array.

Example:

int numbers[5] = {1, 2, 3, 4, 5};
for (int i = 0; i < 5; i++) {
    printf("%d ", numbers[i]);
}

7. 2D Array Example

Input and Output of a 2D Array:

#include <stdio.h>

int main() {
    int matrix[2][2];

    // Input
    printf("Enter 4 elements:\n");
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 2; j++) {
            scanf("%d", &matrix[i][j]);
        }
    }

    // Output
    printf("Matrix:\n");
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 2; j++) {
            printf("%d ", matrix[i][j]);
        }
        printf("\n");
    }

    return 0;
}

8. Advantages of Arrays

• Efficient storage and retrieval of multiple elements.
• Easy to iterate and manipulate using loops.
• Useful for data structures like matrices, stacks, and queues.

9. Limitations of Arrays

• Fixed size: Once defined, the size of an array cannot be changed.
• Stores only one type of data.
• Insertion and deletion operations are not efficient.