2、>main(){floatr,s,l;printf("pleaseinputr:");scanf("%f”,&r);if(r>=0){s=pi*r*r;l=2*i*r;printf("theareais%f",s);printf("thecircumferenceis%f",l);}elseprintf("inputerror!");}3、函数y=f(x)可表示为：2x+1(x<0)y=0(x=0)2x-1(x>0)编程实现输入一个x值，输出y值。main(){intx,y;scanf(“%d”,&x);I
3、f(x<0)y=2*x+1;If(x>0)y=2*x-1;If(x==0)y=0;printf(“%d”,y);}28计算机程序设计基础（c语言）习题编程题4、编写一个程序,从4个整数中找出最小的数,并显示此数。main(){inta,b,c,d,t;scanf(“%d,%d,%d,%d”,&a,&b,&c,&d);if(a>b){t=a;a=b;b=t;}if(a>c){t=a;a=c;c=t;}if(a>d){t=a;a=d;d=t;}printf(“min=%d”,a);}5．有一函数当x<0时y=1，当x>0时
4、，y=3，当x=0时y=5，编程，从键盘输入一个x值，输出y值。main(){intx,y;scanf("%d",&x);if(x<0)y=1;elseif(x==0)y=5;elsey=3;printf("x=%d,y=%d",x,y);}6．从键盘输入两个数，求出其最大值（要求使用函数完成求最大值，并在主函数中调用该函数）main(){floatmax(floatx,floaty);floata,b,m;scanf("%f,%f",&a,&b);m=max(a,b);printf("Maxis%f",m);}f
5、loatmax(floatx,floaty){floattemp;if(xmain(){intyourAge,hisAge;printf("Pleaseenteryourage:");scanf("%d",&yourAge);/*输入你的年龄yourAge*/printf("Pleaseenteryourfr
6、iend'sage:");scanf("%d",&hisAge);/*输入你朋友的年龄hisAge*/if(yourAge>=hisAge) {printf("Youareolder!Yourageis=%d",yourAge); }if(hisAge>yourAge) {printf("Yourfriendisolder!HisAgeageis=%d",hisAge); }}8、键盘输入2个加数，再输入答案，如果正确，显示“right”，否则显示“error”#include“stdio.h”main(){int
7、a,b,c;printf(“pleaseinputaandb”);scanf(%d,%d”,&a,&b);printf(“pleaseinputtheanswerfora+b”);scanf(%d”,&c);if(c==a+b)printf(“right”);elseprintf(“error”);}9.编一程序每个月根据每个月上网时间计算上网费用，计算方法如下：要求当输入每月上网小时数,显示该月总的上网费用(6分)main(){inthour;floatfee;printf(“pleaseinputhou
8、r:”);28计算机程序设计基础（c语言）习题编程题scanf(“%d”,&hour);if(hour<=10)fee=30;elseif(hour>=10&&hour<=50)fee=3*hour;elsefee=hour*2.5;printf(“Thetotalfeeis%f”,fee);}10
