软硬件系统编程PPT (9).pdf

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1、计算机与二进制计算机与二进制 Computer and the Binary Number System DDecimal ecimal MechanicalMechanical C Co omputingmputing DeviceDevice Decimal number system has only ten(10)digits from 0 to 9.It is the numerical base most widely used by humans.Early mechanical calculators are decimal digital machines.Number va

2、lues are represented by gear wheels and each digit of a number has its own wheel.E.g.A cascade of four gears can represent a number from 0 to 9999 3 The decimal system has 10 symbols,which indicates 10 stabale states to correspond to it.Using 10 states in electronic devices is very difficult.Using 2

3、 states in electronic devices is very easy.DDecimal ecimal MechanicalMechanical C Co omputingmputing DeviceDevice Binary Number System The modern binary number system was devised by German mathematician Leibniz represent numeric values using two different symbols:typically 0(zero)and 1(one).The Chin

4、ese Eight Diagrams of Fuxi involved Leibniz discovery of a de facto representation of the binary number system in the sixty-four-hexagram Fu Xi Yijing.4 Two complementary forces generate four aggregates:named lesser yin(少陰少陰,shaoyin),greater yin(太陰太陰;taiyin,which also refers to the Moon),lesser yang

5、(少陽少陽,shaoyang),and greater yang(太陽太陽;taiyang,which also refers to the Sun).Four aggregates generate eight trigrams:named Heaven,Earth,Thunder,Water,Mountain,Wind,Flame,Lake 6 bits(0 or 1)can represent 64 hexagram Computers use binary numeral system Everything in the universe Reasons for use of bina

6、ry system in computers There are many advantages to using binary codes in computers Binary devices are simple and easy to build.Using 2 stable states in electronic devices is very easy.Simple arithmetic operations Binary has only two symbols,0 and 1.Its easy to convert to decimal Correspond to logic

7、al operations Logic is actually for True or False,corresponding to two states X 1X 2YRV1V2I Inputnput OOutput utput X1 X2 Y False False False False True False True False False True True True I Inputnput OOutput utput X1 X2 Y 0 0 0 0 1 0 1 0 0 1 1 1 E.g So.No matter how powerful the computer is,how r

8、ich the information can be processed,the computer hardware can understand only 0 and 1“Summary:computers can directly understand only two binary codes;All information that needs to be stored and processed by the computer must be converted to binary.Please think about:Why can computers handle text,images,videos,and music?