Note The bitwise operators count the positions of bits from right to left, so bit 0 is the in Visual Studio .NET

Encoder PDF 417 in Visual Studio .NET Note The bitwise operators count the positions of bits from right to left, so bit 0 is the

Similarly, if you want to set the bit at position 6 to 1, you can use a bitwise OR (|) operator. The following complicated expression is based on the compound assignment operator |=:

bits |= (1 << 6)

The trouble with these examples is that although they work, it s not clear why or how they work. They re complicated, and the solution is a very low-level one: it fails to create an abstraction of the problem that it solves.

You might have noticed some unfamiliar symbols in the expressions shown in these examples in particular, ~, <<, |, and &. These are some of the bitwise and shift operators, and they are used to manipulate the individual bits held in int and long data types. The NOT (~) operator is a unary operator that performs a bitwise complement. For example, if you take the 8-bit value 11001100 (204 decimal) and apply the ~ operator to it, you obtain the result 00110011 (51 decimal) all the 1s in the original value become 0s, and all the 0s become 1s.

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The left-shift (<<) operator is a binary operator that performs a left shift. The expression 204 << 2 returns the value 48. (In binary, 204 decimal is 11001100, and left-shifting it by two places yields 00110000, or 48 decimal.) The farleft bits are discarded, and zeros are introduced from the right. There is a corresponding right-shift operator >>. The OR (|) operator is a binary operator that performs a bitwise OR operation, returning a value containing a 1 in each position in which either of the operands has a 1. For example, the expression 204 | 24 has the value 220 (204 is 11001100, 24 is 00011000, and 220 is 11011100). The AND (&) operator performs a bitwise AND operation. AND is similar to the bitwise OR operator, except that it returns a value containing a 1 in each position where both of the operands have a 1. So 204 & 20 is 8 (204 is 11001100, 24 is 00011000, and 8 is 00001000). The XOR (^) operator performs a bitwise exclusive OR operation, returning a 1 in each bit where there is a 1 in one operand or the other but not both. (Two 1s yield a 0 this is the exclusive part of the operator.) So 204 ^ 24 is 212 (11001100 ^ 00011000 is 11010100).

Let s pull back from the preceding low-level solution for a moment and stop to remind ourselves what the problem is. We d like to use an int not as an int but as an array of 32 bits. Therefore, the best way to solve this problem is to use an int as if it were an array of 32 bits! In other words, what we d like to be able to write to access the bit at index 6 of the bits variable is something like this:

bits[6]

And, for example, to set the bit at index 6 to true, we d like to be able to write:

Unfortunately, you can t use the square bracket notation on an int it works only on an array or on a type that behaves like an array. So the solution to the problem is to create a new type that acts like, feels like, and is used like an array of bool variables but is implemented by using an int. You can achieve this feat by de ning an indexer. Let s call this new type IntBits. IntBits will contain an int value (initialized in its constructor), but the idea is that we ll use IntBits as an array of bool variables. Tip The IntBits type is small and lightweight, so it makes sense to create it as a structure rather