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được hiển thị bằng cách sử dụng những gì được gọi là một bảng sự thật. Cho thấy điều này, đối với các kết hợp khác nhau có thể của các toán hạng, kết quả là. Bảng sự thật cho & như sau:Đối với mỗi hàng và sự kết hợp cột, kết quả của & kết hợp hai là nhập cảnh tại các giao lộ của các hàng và cột. Bạn có thể thấy cách làm việc này trong một ví dụ | Chapter 2 There are six bitwise operators bitwise AND bitwise OR A bitwise exclusive OR bitwise NOT shift right shift left The next sections take a look at how each of them works. The Bitwise AND The bitwise AND is a binary operator that combines corresponding bits in its operands in a particular way. If both corresponding bits are 1 the result is a 1 bit and if either or both bits are 0 the result is a 0 bit. The effect of a particular binary operator is often shown using what is called a truth table. This shows for various possible combinations of operands what the result is. The truth table for is as follows Bitwise AND 0 1 0 0 0 1 0 1 For each row and column combination the result of combining the two is the entry at the intersection of the row and column. You can see how this works in an example char letterl A letter2 Z result 0 result letterl letter2 You need to look at the bit patterns to see what happens. The letters A and Z correspond to hexadecimal values 0x41 and 0x5A respectively see Appendix B for ASCII codes . The way in which the bitwise AND operates on these two values is shown in Figure 2-8. 82 Data Variables and Calculations You can confirm this by looking at how corresponding bits combine with in the truth table. After the assignment result will have the value 0x40 which corresponds to the character 0 . Because the produces zero if either bit is zero you can use this operator to make sure that unwanted bits are set to 0 in a variable. You achieve this by creating what is called a mask and combining with the original variable using . You create the mask by specifying a value that has 1 where you want to keep a bit and 0 where you want to set a bit to zero. The result of ANDing the mask with another integer will be 0 bits where the mask bit is 0 and the same value as the original bit in the variable where the mask bit is 1. Suppose you have a variable letter of type char where for the purposes of illustration you want to eliminate the high order 4
