实验 3 简单的分支与循环结构

/计算圆面积/
#include<stdio.h>
int main()
{
    double r,s;
    printf("enter r:");
    scanf("%lf",&r);
    if(r>0){
        s=r*r;
        printf("s=%.2f
",s);
    }
        else if(r<=0){
            printf("you are wrong
");
        }
    return 0;
}

#include<stdio.h>
int main()
{
    int c1,c2,c3,c4;
    scanf("%d%d",&c1,&c2);
    printf("%d
",c1+c2);
    getchar();
    c3=getchar();
    c4=getchar();
    printf("%d
",c3+c4);
    return 0;
}

#include<stdio.h>
int main()
{
    int c1,c2,c3,c4;
    scanf("%c%c",&c1,&c2);
    printf("%c%c
",c1,c2);
    getchar();
    c3=getchar();
    c4=getchar();
    printf("%c%c
",c3,c4);
    printf("%c%c%c%c
",c1,c2,c3,c4);
    return 0;
}