《毛泽东思想和中国特色社会主义理论体系概论重点难点解析和练习》.docx
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《毛泽东思想和中国特色社会主义理论体系概论重点难点解析和练习》.docx
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《毛泽东思想和中国特色社会主义理论体系概论重点难点解析和练习》
二进制(Binarysystem)
1.acomputerindicatesthedecimalrangeinwhichdataisused:
Binary:
indigitalcircuits,useahighlevel(+5V)toindicate1,andalowlevel(0V)means0.
Inactualcircuits,+4.8,+4.9,+5.0,+5.1canbecountedas1,andthecorresponding+0.1+0.2iscountedas0
2.ifthecomputerusesdecimal,youneedmorelevelleveltorepresenteachcharacter,whichispronetoerrorandthecontrolaccuracyistoohigh
Allthedigits,characters,video,etc.thatthecomputercanhandlearebinary
Binary:
binary
Octal:
octal
Decimal:
decimal
Sixteendecimal:
hex
Representationofnumbersin3.java
Javainthesourcecode(.Java),digitalrepresentation,usingthedecimal,octal,sixteenhexadecimal
Intnum1=123;//decimal
System.out.println(num1);
Intnum2=0123;//octal
System.out.println(num2);
IntNum3=0x123;//sixteenhexadecimal
System.out.println(Num3);
Javasourcecodemustbecompiledintobytecode(.Class)toexecuteinJVM.Inthiscompilation,allthenumbersareconvertedintobinaryrepresentationsbythecompiler.
4.hexadecimalconversion
Decimalbinaryoctalsixteendecimal
0000
1111
21022
31133
410044
510155
611066
711177
81000108
91001119
10101012A
11101113B
12110014C
13110115D
14111016E
15111117F
16100002010
Amethodofconvertingdecimal123intobinary,octal,andsixteendecimalsystems:
(1)manualconversion:
decimalconversiontoNhexadecimal,usingNexcept,countingtheremainderfromthebottomup
(2)theuseofcalculators:
theoperatingsystemcomeswiththecalculator,therearehexadecimalconversionfunction
(3)useJavaAPI:
Integer.toBinaryString(),/Integer,.ToOctalString(),/Integer,.ToHexString()/Integer.toString(Num,radix)
Practisenextclass:
(1)donotuseAPItoconvertanintegerintobinary
Convertsbinarytodecimal,octal,andsixteenhexadecimal
(1)manualcalculation
(2)usecalculator
(3)usingAPI:
Integer.parseInt(s,2)/Integer.valueOf(s,2)canconvertbinarytodecimal
Octal:
anoctalnumbercanberepresentedbyabinarynumberthree
Sixteenhexadecimal-asixteendecimalnumbercanbeexpressedinfourbinarynumbers
Therepresentationof5.positiveintegersandnegativeintegersinacomputer
Positiveinteger:
+123positive,astheoriginalcode,complementcomplementform
Binarycode:
0000000000000000(0000000001111011forenough32bit)
One'scomplementsays:
00000000000000000000000001111011
Binarycomplementsaid:
0000000000000000,0000000001111011
Negativeinteger:
-123firstasthesignbit,bybitreversecomplement,complementiscomplement+1
Binarycode:
10000000000000000000000001111011
One'scomplementsays:
111111*********11111111110000100
Binarycomplementsaid:
111111*********1,1111111110000101
Thenumberstoredinacomputeristhecomplement.
Tips:
howtocomplementnegativeconversioniscorrespondingtotheoriginalcode:
bitwisenot+1.
Binaryrelationalapplications
6.representationrangeandoverflowproblemofinteger
Representstherangeofbytes
Byte1bytes-128~+127
Short2bytes-32768~+32767
Int4bytes-2147483648~+2147483647
Long8bytes-2^63~+2^63-1
Interviewquestions:
IntI1=2147483647;
IntI2=1;
IntI3=i1+i2;
Avoidoverflowproblemswithintegerarithmetic:
java.math.BigInteger
Interviewquestions:
FloatF1=2.1f;
FloatF2=0.1f;
FloatF3=f1+f2;//2.19999998
Avoidoverflowproblemswithfloating-pointarithmetic:
java.math.BigDecimal
7.themethodoftimerepresentedinacomputer
Atthebottomofthecomputer,youcanonlyhandlebinarynumbers.Thesourcecodeisrepresentedbydecimal/octal/sixteenhexadecimalnumbers
Thecomputerusesalongvaluetoholdthetimeindicatinghowmuchtimeittakestodisplaythetimefromthefirstyearofthecomputer(1970-0:
0:
0GMT)
8.thememorysizecanbeusedinthecomputer
WindowsXP32bitoperatingsystem:
theoperatingsystemusesmemorytousea32bitbinarynumbertoaddressthememoryaddress.
0000000000000000,0000000000000000
0000000000000000,0000000000000001
0000000000000000,0000000000000010
......
1111111111111111,1111111111111111,2^32,about4G
Windows764bitoperatingsystem:
theoperatingsystemusesmemorytousea64bitbinarynumbertoaddressthememoryaddress.Addressingrange:
0-2^64
2^101Kilo
2^201Mega
2^301Giga
2^401Tega
2^501Pera
2^601E
2^701Z
2^801Yota
Howtostorecharacterdatain9.java
Sincethecomputercanonlystoreandprocessnumbers,characterscanalsobeconvertedtonumbers.Assignacorrespondingnumbertoeachcharacterinanumberofcharacters---characterencoding.Theworld'smajorcharacterencodingscheme:
(1)ASC:
encodesacharacterwith8binarydigits,representingatmost256characters
(2)Unicode:
encoding16characterswithbinarynumberscanrepresent65536characters,enoughtoencodeallthemajorsymbolsoftheworld'smaintext.
TherangeofChinesecharactersinUnicodecode:
19968-40869(0x4E00~0x9FA5)
(3)ISO8859-1:
encodedigitswith8bitbinarynumbers,upto256characters,andencodecommoncharactersinWesterneurope.
(4):
GB2312/GBK/GB18030encodingthedigitalby16binaryChinese,formulatedbytheNationalStandardizationCommittee,theChineseinsimplifiedandtraditionalChinesecharactersencoding
(5)Big5:
encodingdigitsinbinary16bits,developedbyTaiwan.
Exercises:
Lettheuserenterastringfromthekeyboard,usingtheprogramstatisticsinthestringofhowmanyEnglishcharacters,howmanyChinesecharacters,digitalcharacters,andothercharacters?
Therootcauseofthestringgarbledproblem:
theencodingofstoreddataandtheacquisitionofdataaredifferent
Howtorepresentcolorsin10.java
Computer32bittruecolormeaning:
use32bitbinarynumbertorepresentacolor.
0-7:
tableAlphatransparency
8-15:
Redcontent
16-23:
greencontent
24-31:
meansthecontentofblue
Threeprimarycolors:
red,green,andblue.Afterthedifferentproportionsofthesethreecolors,theycanbeblendedinanyothercolor.Incomputer,8binarynumbersareusedtodescribethecontentofaprimarycolor.
Red:
00000000~111111110~255
Green:
00000000~111111110~255
Blue:
00000000~111111110~255
Commoncolors:
Purered:
1111111100000000,00000000
Darkred:
1010101000000000,00000000
Puregreen:
0000000011111111,00000000
Pureblue:
0000000000000000,11111111
Black:
0000000000000000,00000000
White:
111111*********1,11111111
Blackgrey:
0000111100001111,00001111
Lightgrey:
111100*********0,11110000
Thatisoutofproportionof1:
1:
1primarycolors:
blackandwhiteash,thegreaterthevalueofthesmallerandmorewhite,black
Yellow:
111111*********1,00000000
Magenta:
1111111100000000,11111111
Orange:
25016010(decimalnotation)
Demo:
generaterandomauthenticationcode
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