某公司管理流程图(英文版).pptx

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1、Ch5 Selection StatementsProgramming ConstructProgramming Construct1）We divide the basic programming construct into three types:Sequential Structure 、Selection Structure and Loop Structure.2）Flow Chart(流程图)：is a graphical representation in which specific symbols and necessary letters are used to desc

2、ribe the steps.3）The flow chart about the three basic programming construct is as follows：ABconditionABconditionASequential structureSelection StructureSelection Structure1、relation operator andrelation expression 2、logical operators and logical expression3、if statements4、switch statements5、examples

3、Chapter OutlineThree forms：（1）if（expression）statements（2）if（expression）statements1elsestatements2（3）if（expression1）statements1elseif(expression2)statements2elseif(expression3)statements3elseif（expressionm）statementsmelsestatementsnexexex第第五五章章选选择择结结构构If语语句句的的形形式式Brief Summary Forme1：if（expression）st

4、atementsexpressionstatementsF(0)T(not0)ex：if(xy)printf(“%d”,x);Firstly,solvetheexpression.Ifthevalueoftheexpressionisnotzero，thenthecorrespondingststementsequenceisexcuted.Ifnoneoftheexpressionisfalse,thenexcutethestatementsafterifderectly.第第五五章章选选择择结结构构If语语句句的的形形式式exampleexpressionstatements1statem

5、ents2TFex：if(xy)printf(“%d”,x);elseprintf(“%d”,y);Form2：if（expression）statements1elsestatements2第第五五章章选选择择结结构构If语语句句的的形形式式exampleexpression1expression2expression3expression4statements1 statements2statements3statements4 statements5FFFFTTTTex：if(number500)cost=0.15;elseif(number300)cost=0.10;elseif(nu

6、mber100)cost=0.075;elseif(number50)cost=0.05;elsecost=0;Form3：nested-if statements第第五五章章选选择择结结构构If语语句句的的形形式式example（1）Theexpressionofthreeformsbehindif-statementsalwaysislogicalorrelationexpression.DCL of three if-statements forms：（2）Inform2andforme3，thereisasemicoloninfrontofelse,alsointheendofalls

7、tatements.（3）Behindiforelse,itmayincludeonlyoneoperatestatements,alsoincludemanystatements,butshouldbedrawedtogetherwithbrace.()第第五五章章选选择择结结构构If语语句句的的形形式式Ex:#include main()int x,y;scanf(“%d,%d”,&x,&y);if(xy)x=y;y=x;else x+;y+;printf(“%d,%dn”,x,y);Compile Error!ex：if(a+ba&c+ab)s=0.5*(a+b+c);area=sqrt

8、(s*(s-a)*(s-b)*(s-c);printf(“area=%6.sf”,area);elseprintf(“itisnotatrilateral”);Notice：Thebrace(“”)souterfaceneednotsemicolon。Becauseinthebrace()thereisafullcompoundstatement.第第五五章章选选择择结结构构If语语句句的的形形式式 original program:main()floata,b,t;scanf(“%f,%f”,&a,&b);if(ab)t=a;a=b;b=t;printf(“%5.2f,%5.2f”,a,b)

9、;ex1：Input twe real numbers，please output there numbers according to the order of little to big.Need three float variables:a,b,t第第五五章章选选择择结结构构If语语句句举举例例ex2：Input three real numbers，please output there numbers according to the order of little to big.original program:main()floata,b,c,t;scanf(“%f,%f,%f

10、”,&a,&b,&c);if(ab)t=a;a=b;b=t;if(ac)t=a;a=c;c=t;if(bc)t=b;b=c;c=t;printf(“%5.2f,%5.2f,%5.2f”,a,b,c);第第五五章章选选择择结结构构If语语句句举举例例Return#include main()int a,b;printf(Enter integer a:);scanf(%d,&a);printf(Enter integer b:);scanf(%d,&b);if(a=b)printf(a=bn);else printf(a!=bn);ex3：Iputtwonumbers,decidethemtob

11、eequallyornot.Result：Enter integer a:12 Enter integer b:12 a=b Result：Enter integer a:12 Enter integer b:9 a!=b 第第五五章章选选择择结结构构If语语句句嵌嵌套套举举例例ReturnGeneralform：expression1？expression2：expression3 Condition operator commands three operate objects,it is a operator alonely in C language.ex：max=(ab)?a:b;E

12、qual to：if(ab)max=a;elsemax=b;第第五五章章选选择择结结构构条条件件运运算算符符Condition operator DCL：（1）Executionorder：Firstly,solve the expression 1，If the value is ture,then solve the expression 2,this moment here is the value of whole expressions.If the value is false,then solve the expression 3,this moment here is the

13、value of whole expressions.ex：max=(ab)?a:b;If a=3,b=4;max=4；If a=6，b=4;max=6；第第五五章章选选择择结结构构条条件件运运算算符符（2）Condition operator overmatch assigned operator,but under relation and arithmetic operator.（3）Condition operators combined direcion is from right to left.ex1：max=(ab)?a:b;max=ab?a:b;ex2：max=ab?a:b+

14、1;max=ab?a:(b+1);ex3：max=ab?a:cd?c:d；max=ab?a:（cd?c:d）;Suppose a=1,b=2,c=3,d=4第第五五章章选选择择结结构构条条件件运运算算符符（4）Condition operator cannt replce ordinary if-statements,only when the embed statements in it is assigned statements(and two branches assign to the same variable).ex：if(ab)printf(“%d”,a);elseprintf

15、(“%d”,b);printf(“%d”,ab?a:b);（5）Thetypeofexpression1andexpression2canbesame,alsobedifferent.ex：intx;x?a:b;ex：xy?1:1.5;第第五五章章选选择择结结构构条条件件运运算算符符Ex5:Input a letter，iudge it is a capital letter or not ，if is，then change it to lower-case letter；if not，then nothing changed。Finally,output this letter。main(

16、)charch;scanf(“%c“,&ch);ch=(ch=A&ch=Z)?(ch+32):ch;printf(“%c“,ch);第第五五章章选选择择结结构构条条件件运运算算符符Returnex6：Function-1（x0)y=Writeaprogramme，inputthevalueofx.Thenouputy.main()float x;int y;scanf(“%f”,&x);if(x 0)y=1;printf(“n%f,%d”,x,y);第第五五章章选选择择结结构构If语语句句嵌嵌套套举举例例ReturnAlgorithm 2 2：input x input x ifx0 y=-1

17、 ifx0 y=1 ifx0 y=1 output y output yAlgorithm 3：inputxifx0y=-1else：ifx=0y=0else：y=1ouputy第第五五章章选选择择结结构构If语语句句嵌嵌套套举举例例p1：main()floatx;inty;scanf(“%f”,&x);if(x=0)if(x0)y=1;elsey=0;elsey=-1;p3：modifyto：y=-1;if(x!=0)if(x0)y=1;elsey=0;p4：modifyto：y=0;if(x=0)if(x0)y=1;elsey=-1;第第五五章章选选择择结结构构If语语句句嵌嵌套套举举例例Return#include main()int x,y;printf(Enter an integer:);scanf(%d,&x);y=x;if(yabsolute value:%dn,x,y);ex运行：Enter an integer:-12 integer:-12-absolute value:12第第五五章章选选择择结结构构If语语句句嵌嵌套套举举例例