What is an array?
In C, an array is a data structure that stores multiple values of the same data type in a single variable.
Instead of creating many variables, you use one array to store all values together.
💡 Simple idea
An array is like a row of boxes, each holding one value.
Why use arrays?
- 📦 Store multiple values in one variable
- ⚡ Faster access using indexes
- 🧹 Cleaner and organized code
- 📊 Useful for loops and data processing
Declaring an array
int numbers[5];
This creates an array that can store 5 integers.
Initializing an array
int numbers[5] = {10, 20, 30, 40, 50};
Accessing array elements
Array elements are accessed using index numbers (starting from 0).
printf("%d", numbers[0]); // 10
printf("%d", numbers[2]); // 30
How arrays work in memory
- All elements are stored in consecutive memory locations
- Each element has the same data type
- Index helps calculate memory address
Looping through arrays
for(int i = 0; i < 5; i++) {
printf("%d\n", numbers[i]);
}
Types of arrays
- 1D arrays — single row
- 2D arrays — rows and columns (matrices)
- Multi-dimensional arrays
Example of 2D array
int matrix[2][2] = {
{1, 2},
{3, 4}
};
Common mistakes
- Accessing out-of-bounds index
- Not initializing arrays properly
- Confusing size and index
⚠️ Important
Array indexes in C always start from 0. Accessing invalid indexes can cause undefined behavior.
Summary
Arrays in C are used to store multiple values of the same type in a single variable, using continuous memory and index-based access.
They are one of the most important and widely used data structures in C programming.