C程序设计ch04 判定、分支和循环.ppt

第四章判定、分支和循环/*absolutevalue*/
#include<stdio.h>
main()
{intx,y;
printf("Enteraninteger:");
scanf("%d",&x);
y=x;
if(y<0)
y=-y;
printf("\ninteger:%d-->absolutevalue:%d\n",x,y);
}引入复合语句：用{…}括起来的一组语句
一般形式：{[数据说明部分；]
执行语句部分；
}
expr例if(x>y)max=x;
elsemax=y;应用扩展例百分制成绩转换为五级制p122
80to100Honours
60to79FirstDivision
50to59SecondDivision
40to49ThirdDivision
0to39Fail

例累进电费p124例根据税前收入计算税后收入/*chartype*/
#include<stdio.h>
main()
{charc;
printf("Enteracharacter:");
c=getchar();
if(c<0x20)printf("Thecharacterisacontrolcharacter\n");
elseif(c>='0'&&c<='9')printf("Thecharacterisadigit\n");
elseif(c>='A'&&c<='Z')printf("Thecharacterisacapitalletter\n");
elseif(c>='a'&&c<='z')printf("Thecharacterisalowerletter\n");
elseprintf("Thecharacterisothercharacter\n");
}
例：if(a==b)
if(b==c)
printf(“a==b==c”);
else
printf(“a!=b”);/*SelectLabel*/
#include<stdio.h>
main()
{intc;
printf("Entermornorhorother:");
c=getchar();
switch(c)
{case'm':printf("\nGoodmorning!\n");break;
case'n':printf("\nGoodnight!\n");break;
case'h':printf("\nHello!\n");break;
default:printf("\n????????\n");break;
}
}switch(表达式)
{caseE1:
语句组1;
break;
caseE2:
语句组2;
break;
…….
caseEn:
语句组n;
break;
[default:
语句组;
break;]
}例百分制成绩转换为五级制p122
80to100Honours
60to79FirstDivision
50to59SecondDivision
40to49ThirdDivision
0to39Fail
用SwitchStatement.例用if和goto语句构成循环，求1+2+…+100例从键盘输入一组数据，以0结束输入，求数据和例pp135RANGEofNumbers:
Asurveyofthecomputermacketshowthatpersonalcomputersaresoldatvaryingcosts
bythevendors.Thefollowingisthelistofcosts(inhundreds)quotedbysomevendors:
35.00,40.50,25.00,31.25,68.15,
47.00,26.65,29.00,53.45,62.50
Determinetheaveragecostandtherangeofvalues.例pp136Pay-BillCalculations:
Amanufacturingcompanyhasclassifieditsexecutivesintofourlevelsforthebenefitofcertainperks.Thelevelsandcorrespondingperksareshownbelow:
Perks
Level------------------------------------------------------------------
ConveyanceEntertainment
allowanceallowance
11000500
2750200
3500100
4250----
Anexecutive’sgrosssalaryincludesbasicpay,houserentallowanceat25%