Bool array

In a C# program, a bool array requires one byte per element. It can store many true and false values, and are easy to use.

Boolean arrays are simple and allow for safe and clear code. They are not optimally memory-efficient, but often they are good enough.

To start, we allocate and initialize bool arrays. The syntax is the same as other arrays, in that you need to specify the array length inside the square brackets.

using System;

// Initialize new bool array.
bool[] array = new bool[10];
array[0] = false;
array[1] = true;
array[2] = false;
array[3] = true;

// Loop through all values.
foreach (bool value in array)
{
    Console.WriteLine(value);
}
False
True
False
True
False
False
False
False
False
False

Memory

The bool value can be expressed with a single bit in memory—one means true and zero means false. However, the bool type in C# is expressed in eight bits, or one byte.

using System;

//
// Initialize new bool array.
//
bool[] array = new bool[1000000];
//
// Initialize each other value to true.
//
for (int i = 0; i < array.Length; i += 2)
{
    array[i] = true;
}
Size of the array in memory: 1,000,012 bytes [CLRProfiler].
Each bool requires 1 byte.
Array reference requires 12 bytes.

Sorting bool arrays is useful for certain algorithms. It can help methods that favor some object, but do not want to remove objects.

Arguments

As with other arrays, you can pass bool arrays as arguments by using the bool[] type for the parameter. You can also return bool arrays from methods with the same type.

BitArray

There is a BitArray class in the System.Collections namespace. This is more compact than bool arrays, and can reduce memory usage.

The program showed that elements in bool arrays are initialized to false automatically. We saw that bool arrays require one byte for each element.