《计算机科学导论》课件Unit 4Data Operations知识讲稿.pptVIP

* Applications OR: Setting specific bits Figure 4.3 Example of setting specific bits of a bit pattern * Applications XOR: Flipping specific bits The XOR operator is used to flip specific bits (0 becomes 1 and vice versa). The flip operation is functionally similar to the NOT operator. To flip a specific bit in the target bit pattern, the corresponding bit in the flipping mask is set to 1. Otherwise, to leave a bit in the target bit pattern unchanged, the corresponding bit in the mask is set to 0. Figure 4.4 shows an example of flipping specific bits. * Applications XOR: Flipping specific bits Figure 4.4 Example of flipping specific bits * Applications XOR: Flipping specific bits Other interesting applications of XOR operator are to do parity check of bit strings and to verify whether bytes sent across a network were corrupted and need retransmission, or they were sent without errors. There are interesting applications of XOR operator. XOR can be used to exchange two numbers without using any intermediate variable. If we have aand b then after taking three XOR operations, we will finally exchange the value of a and b. * Arithmetic Operations on integers Arithmetic Operations on reals 4-2 Arithmetic Operations * Arithmetic operations on integers The four basic arithmetic operations are addition, subtraction, multiplication, and division. These operations can apply to both integers and floating-point numbers. Among the four basic arithmetic operations, the addition and subtraction operations are fundamental and essential. So we focus on addition and subtraction operation of integers in this section as multiplication and division essentially boil down to 【归结为】the addition and subtraction. The corresponding procedure of multiplication and division operations can be found in books on computer architecture, such as “Computer Organization and Architecture: Designing for performance * Arithmetic operations on integers Addition and subtraction in two