表格模板-Chart流程图is 精品.ppt

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1、Programming 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 describe the steps.3）The flo

2、w chart about the three basic programming construct is as follows：ABconditionABconditionASequential structureSelection StructureSelection Structure1、relation operator and relation expression 2、logical operators and logical expression3、if statements4、 switch statements5、 examplesChapter OutlineThree

3、forms： （1）if（expression）statements （2）if（ expression ） statements 1 else statements 2 （3）if（ expression 1） statements 1 else if (expression 2) statements 2 else if (expression 3) statements 3 else if（expression m） statements m else statements nexexex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 if（express

4、ion）statementsexpressionstatementsF(0)T(not 0)ex： if(xy) printf(“%d”,x); Firstly,solve the expression. If the value of the expression is not zero，then the corresponding ststement sequence is excuted. If none of the expression is false,then excute the statements after if derectly.第第五五章章选选择择结结构构If语语句句

5、的的形形式式exampleexpressionstatements1statements2TFex： if(xy) printf(“%d”,x); else printf(“%d”,y);if（expression）statements1 else statements2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exampleexpression1expression2expression3expression4statements1statements2statements3statements4 statements5FFFFTTTTex： if (number500) cost

6、=0.15; else if (number300) cost=0.10; else if (number100) cost=0.075; else if (number50) cost=0.05; else cost=0;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）The expression of three forms behind if-statements always is logical or relation expression.DCL of three if- statements forms（2）In

7、 form2 and forme3，there is a semicolon in front of else, also in the end of all statements.（3）Behind if or else,it may include only one operate statements,also include many statements ,but should be drawed together with brace.( )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

8、,&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(s*(s-a)*(s-b)*(s-c); printf(“area=%6.sf”,area); else printf(“it is not a trilateral”); Notice：The brace( “”)s outer face need not semicolon。Because in the brace() there is a full compoun

9、d statement .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() float a,b,t; scanf(“%f,%f”,&a,&b); if(ab) t=a;a=b;b=t; printf(“%5.2f,%5.2f”,a,b); 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

10、ex2：Input three real numbers，please output there numbers according to the order of little to big.original program : main() float a,b,c,t;scanf(“%f ,%f,%f”,&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 ma

11、in() 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 ：Iput two numbers ,decide them to be equally or not.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

12、结构构If语语句句嵌嵌套套举举例例ReturnGeneral form：expression1？expression2：expression3 Condition operator commands three operate objects,it is a operator alonely in C language.ex： max=(ab) ? a : b;Equal to ： if(ab) max= a; else max=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）Execution order ： Firstly,solv

13、e 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 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

14、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+1;max= ab ? a : (b+1);ex3：max= ab ? a : c d ? c:d ；max= ab ? a : （c d ? c:d）;Su

15、ppose 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); else printf(“%d”,b);printf(“%d”,ab?a:b);（5）The type of express

16、ion 1 and expression 2 can be same,also be different.ex： int x; 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()char ch;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=Write a programme，input the value of x. Then ouput y.main( ) float x ; int