What is an Array?

Think of an array as a row of lockers in a school hallway. Each locker has a number (starting from 0), and you can store something in each locker. Similarly, an array is a collection of variables of the same data type stored in consecutive memory locations.

Why Use Arrays?

Instead of creating separate variables like:

int student1_score = 85;
int student2_score = 92;
int student3_score = 78;
// ... and so on for 100 students!

You can use an array:

int scores[100]; // One array to store all 100 scores!

Array Declaration

The basic syntax for declaring an array is:

data_type array_name[size];

Examples:

int numbers[5];        // Array of 5 integers
char letters[10];      // Array of 10 characters
float prices[3];       // Array of 3 floating-point numbers

Array Initialization

You can initialize arrays in several ways:

Method 1: Initialize during declaration

int ages[4] = {25, 30, 35, 40};
char grades[5] = {'A', 'B', 'C', 'D', 'F'};

Method 2: Initialize without specifying size

int numbers[] = {10, 20, 30, 40, 50}; // Size automatically becomes 5

Method 3: Partial initialization

int values[5] = {1, 2}; // First two elements are 1,2; rest are 0

Accessing Array Elements

Array elements are accessed using index numbers starting from 0.

int scores[5] = {85, 92, 78, 96, 88};

printf("%d", scores[0]); // Prints 85 (first element)
printf("%d", scores[2]); // Prints 78 (third element)
printf("%d", scores[4]); // Prints 88 (last element)

Array Index Table

Index	Value	Description
0	85	First element
1	92	Second element
2	78	Third element
3	96	Fourth element
4	88	Fifth element

Modifying Array Elements

You can change array elements by assigning new values:

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

numbers[1] = 25;  // Changes second element from 20 to 25
numbers[2] = 35;  // Changes third element from 30 to 35

// Now array is: {10, 25, 35}

Complete Example

Here's a practical example showing array basics:

#include <stdio.h>

int main() {
    // Declare and initialize an array
    int temperatures[7] = {22, 25, 28, 30, 27, 24, 21};
    
    // Print all temperatures
    printf("Weekly temperatures:\n");
    for(int i = 0; i < 7; i++) {
        printf("Day %d: %d°C\n", i+1, temperatures[i]);
    }
    
    // Modify a temperature
    temperatures[3] = 32; // Change day 4 temperature
    
    printf("\nUpdated temperature for day 4: %d°C\n", temperatures[3]);
    
    return 0;
}

Important Points to Remember

• Array indices start from 0, not 1
• Array size must be specified during declaration (except when initializing)
• All elements in an array must be of the same data type
• Accessing an index outside the array bounds can cause errors
• Array name represents the address of the first element

Arrays are fundamental building blocks in C programming, making it easy to work with collections of related data!