20131002国庆作业例3-4,3-5,3-7

3-4

运行结果1

结果2

结果3

#include<stdio.h>
int main(void)
{
    double x,y;


    printf("Enter x:");
    scanf("%lf",&x);
    if(x<0){
        y=0;
    }
    else if(x<=15){
        y=4*x/3;
    }
    else{
        y=2.5*x-10.5;
    }

    printf("f(%.2f)=%.2f
",x,y);

    return 0;
}

3-5

#include<stdio.h>
int main(void)
{
    double value1,value2;
    char op;

    printf("Type in an expression:");
    scanf("%lf%c%lf",&value1,&op,&value2);

    if(op=='+')
        printf("=%.2f
",value1+value2);
    else if(op=='-')
        printf("=%.2f
",value1-value2);
    else if(op=='*')
        printf("=%.2f
",value1*value2);
    else if(op=='/')
        printf("=%.2f
",value1/value2);
    else
        printf("Unknown operator
");

    return 0;
}

 3-7

#include<stdio.h>
int main(void)
{
    int digit,letter,other;
    char ch;
    int i;
    digit=letter=other=0;
    printf("Enter 10 characters:");
    for(i=1;i<=10;i++){
        ch=getchar();
        if((ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z'))
            letter++;
        else if(ch>='0'&&ch<='9')
            digit++;
        else
            other++;
    }
    printf("letter=%d,digit=%d,other=%d
",letter,digit,other);

    return 0;
}