Bitwise Operators (<<, >>, |, &, ^, ~)
An additional set of operators that is common to virtually all programming languages is the set of operators for manipulating values in their binary formats: the bit operators.
Shift Operators (<<, >>, <<=, >>=)
Sometimes you want to shift the binary value of a number to the right or left. In executing a left shift, all bits in a number's binary representation are shifted to the left by the number of locations specified by the operand on the right of the shift operator. Zeroes are then used to backfill the locations on the right side of the binary number. A right-shift operator does almost the same thing in the opposite direction. However, if the number is negative, then the values used to backfill the left side of the binary number are ones and not zeroes. The shift operators are >> and <<, the right-shift and left-shift operators, respectively. In addition, there are combined shift and assignment operators, <<= and >>=.
Consider the following example. Suppose you had the int value 7, which would have a binary representation of 1111 1111 1111 1111 1111 1111 1111 1001. In Listing 3.36 you right-shift the binary representation of the number7 by two locations.
Listing 3.36. Using the Right-Shift Operator
Output 3.17 shows the results of Listing 3.36.
Because of the right shift, the value of the bit in the rightmost location has "dropped off" the edge and the negative bit indicator on the left shifts by two locations to be replaced with ones. The result is -2.
Bitwise Operators (&, |, ^)
In some instances, you might need to perform logical operations, such as AND, OR, and XOR, on a bit-by-bit basis for two operands. You do this via the &,|, and ^ operators, respectively.
Listing 3.37 demonstrates how to use these bitwise operators. The results of Listing 3.37 appear in Output 3.18.
Listing 3.37. Using Bitwise Operators
In Listing 3.37, the value 7 is the mask; it is used to expose or eliminate specific bits within the first operand using the particular operator expression.
In order to convert a number to its binary representation, you need to iterate across each bit in a number. Listing 3.38 is an example of a program that converts an integer to a string of its binary representation. The results of Listing 3.38 appear in Output 3.19.
Listing 3.38. Getting a String Representation of a Binary Display
Notice that within each iteration of the for loop (discussed shortly), you use the right-shift assignment operator to create a mask corresponding to each bit in value. By using the & bit operator to mask a particular bit, you can determine whether the bit is set. If the mask returns a positive result, you set the corresponding bit to 1; otherwise, it is set to 0. In this way, you create a string representing the binary value of an unsigned long.
Listing 3.38 again used the keyword new, but this time, you instantiated a StringBuilder object, not an array. Chapter 5 covers the concept of instantiation and using the new operator in depth.
Bitwise Assignment Operators (&=, |=, ^=)
Not surprisingly, you can combine these bitwise operators with assignment operators as follows: &=, |=, and ^=. As a result, you could take a variable, OR it with a number, and assign the result back to the original variable, which Listing 3.39 demonstrates.
Listing 3.39. Using Logical Assignment Operators
The results of Listing 3.39 appear in Output 3.20.
Bitwise Complement Operator (~)
The bitwise complement operator takes the complement of each bit in the operand, where the operand can be an int, uint, long, or ulong. ~1, therefore, returns 1111 1111 1111 1111 1111 1111 1111 1110 and ~(1<<31) returns 0111 1111 1111 1111 1111 1111 1111 1111.