What is meant by the term 'Capacity' in a list data structure?

In the List data structure in C#, the Capacity property indicates the number of elements the list can contain without needing to allocate additional memory.

• Capacity is always greater than or equal to the current number of elements (Count).
• When adding elements, if Count exceeds Capacity, the list automatically increases Capacity by allocating a new, larger array and copying the data.

This is important for performance: if the approximate number of elements is known in advance, you can set Capacity to avoid frequent memory reallocations.

Example:

List<int> numbers = new List<int>(10); // Capacity = 10

for (int i = 0; i < 10; i++) {
    numbers.Add(i);
}

Console.WriteLine(numbers.Capacity); // 10

numbers.Add(11); // Capacity will increase, for example, to 20
Console.WriteLine(numbers.Capacity); // 20

Thus, Capacity is the internal size of the array used by the list, and Count is the actual number of elements.