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Introduction To Bitwise Operations


Introduction To Bitwise Operations

Bitwise operators are used to change individual bits in an operand.
The main use of bitwise operations are to perform calculations at a more optimized level as these operations are directly supported by the processor.
  • & (bitwise AND) Takes two numbers as operands and does AND on every bit of two numbers. The result of AND is 1 only if both bits are 1.
    eg: 1010 & 0010 = 0010
  • | (bitwise OR) Takes two numbers as operands and does OR on every bit of two numbers. The result of OR is 1 any of the two bits is 1.
    eg: 1001 | 0010 = 1011
  • ^ (bitwise XOR) Takes two numbers as operands and does XOR on every bit of two numbers. The result of XOR is 1 if the two bits are different.
    eg: 0110 ^ 1000 = 1110
  • << (left shift) Takes two numbers, left shifts the bits of the first operand, the second operand decides the number of places to shift.
    eg: 0101 << 1 = 1010
  • >> (right shift) Takes two numbers, right shifts the bits of the first operand, the second operand decides the number of places to shift.
    eg: 0010 >> 1 = 0001
  • ~ (bitwise NOT) Flips all the bits.
    eg : ~1001 = 0110
*Note : When it comes to shifting bits there are mainly 3 types : Arithmetic Shift, Logical Shift & Circular Shift.
These variations are there to handle the cases where the bits at the edge of the bit field are about to be shifted out of the bit field.

Let's Look At A C# Example

using System;
namespace BitshiftProductions
{
    public class Program
    {
        public static void Main(string[] args)
        {
            int x = 14; // 00001110
            int y = 28; // 00011100
            
            Console.WriteLine("x = " + x + " in binary : " + Convert.ToString(x, 2));
            Console.WriteLine("y = " + y + " in binary : " + Convert.ToString(y, 2));
            
            int k = x|y;
            Console.WriteLine("X OR Y = " + k + " in binary : " + Convert.ToString(k, 2));
            
            k = x&y;
            Console.WriteLine("X AND Y = " + k + " in binary : " + Convert.ToString(k, 2));
            
            k = x^y;
            Console.WriteLine("X XOR Y = " + k + " in binary : " + Convert.ToString(k, 2));
            
            k = x<<2;
            Console.WriteLine("Left Shifted x(14) by 2 places = " + k + " in binary : " + Convert.ToString(k,2));
            k = x>>2;
            Console.WriteLine("Right Shifted x(14) by 2 places = " + k + " in binary : "+ Convert.ToString(k,2));
            
            k = ~x;
            Console.WriteLine("NOT x = " + k + " in binary : "+ Convert.ToString(k,2));
        }
    }
}
x = 14 in binary : 1110
y = 28 in binary : 11100
X OR Y = 30 in binary : 11110
X AND Y = 12 in binary : 1100
X XOR Y = 18 in binary : 10010
Left Shifted x(14) by 2 places = 56 in binary : 111000
Right Shifted x(14) by 2 places = 3 in binary : 11
NOT x = -15 in binary : 11111111111111111111111111110001
*Note : Leading zeros are not printed with Convert.ToString(object, base) method. All these are 32 bit numbers so the actual bit string would have 32 spaces.

Common Use Cases Of Bitwise Operations

using System;
namespace BitshiftProductions
{
    public class Program
    {
        public static void Main(string[] args)
        {
            int num = 8;
            // 1. Dividing By 2
            int k = num >> 1;
            Console.WriteLine("Num = 8, Divide By 2 = " + k);
            // 2. Multiply By 2
            k = num << 1;
            Console.WriteLine("Num = 8, Multiply By 2 = " + k);
            // 3. Checking If A Number Is Odd Or Even
            k = num & 1;//(num & 1) would be non-zero only if x is odd, otherwise the value would be zero.            
            Console.WriteLine("Is num Odd Or Even : " + ((k != 0)?"Odd":"Even"));
            // 4. Check If 2 integers Have Opposite Signs
            Console.WriteLine("Do -100 & 50 have same sign ? : " + ((-100 ^ 50) >= 0));
            // 5. Find log base 2 of 32 bit integer
            int res = 0;
            int temp = num;
            while (temp > 1)
            {
                temp = temp >> 1;
                res++;
            }
            Console.WriteLine("Log Base 2 of NUM(8) : " + res);
        }
    }
}
Num = 8, Divide By 2 = 4
Num = 8, Multiply By 2 = 16
Is num Odd Or Even : Even
Do -100 & 50 have same sign ? : False
Log Base 2 of NUM(8) : 3
I hope to have introduced you to the world of bit manipulation. All the things you learnt today can be easily implemented into your existing projects.
That's it! Hope you learnt something. Support Bitshift Programmer by leaving a like on Bitshift Programmer Facebook Page and be updated as soon as there is a new blog post.
If you have any questions that you might have about Shaders / Unity development / C# in general don't be shy and leave a message on my facebook page or down in the comments.
For more C# development tutorials, go : HERE
For Unity development tutorials, go : HERE

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