例题第2章

2.1

#include<stdio.h>
int main(void)
{
    printf("Hello World!
");


    return 0;
}

2.2

#include<stdio.h>
int main(void)
{
    printf("Programming is fun.
");
    printf("And programming in C is even more fun!
");

    return 0;
}

2.3

#include<stdio.h>
int main(void)
{
    int celsius,fahr;

    fahr=100;
    celsius=5*(fahr-32)/9;

    printf("fahr=%d,celsius=%d
",fahr,celsius);

    return 0;
}

2.4

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

    printf("Enter x(x>=0):
");
    scanf("%lf",&x);
    if(x<=15){
        y=4*x/3;
    }
    else{
        y=2.5*x-10.5;
    }
    printf("y=f(%f)=%.2f
",x,y);

    return 0;
}

2.5

#include<stdio.h>
#include<math.h>
int main(void)
{
    int money,year;
    double rate,sum;

    printf("Enter money:");
    scanf("%d",&money);
    printf("Enter year:");
    scanf("%d",&year);
    printf("Enter rate:");
    scanf("%lf",&rate);
    sum=money * pow(1 + rate,year);
    printf("sum = %.2f
",sum);

    return 0;
}

2.6

#include<stdio.h>
int main(void)
{
    int fahr,lower,upper;
    double celsius;

    printf("Enter lower:");
    scanf("%d",&lower);
    printf("Enter upper:");
    scanf("%d",&upper);
    printf("fahr celsius
");

    for(fahr=lower;fahr<=upper;fahr++){
        celsius=(5.0/9.0)*(fahr-32);
        printf("%d%6.1f
",fahr,celsius);
    }

    return 0;
}

2.7

#include<stdio.h>
int main(void)
{
    int i,n,sum;

    printf("Enter n:");
    scanf("%d",&n);
    sum=0;
    for(i=1;i<=n;i++){
        sum=sum+i;
    }

    printf("Sum of numbers from 1 to %d is %d
",n,sum);

    return 0;
}

2.8

#include<stdio.h>
int main(void)
{
    int denominator,flag,i,n;
    double item,sum;

    printf("Enter n:");
    scanf("%d",&n);

    flag=1;
    denominator=1;
    sum=0;

    for(i=1;i<=n;i++){
        item=flag*1.0/denominator;
        sum=sum+item;
        flag=-flag;
        denominator=denominator+2;
    }
    printf("sum=%f
",sum);

    return 0;
}

2.9

#include<stdio.h>
int main(void)
{
    int i,n;
    double product;

    printf("Enter n:");
    scanf("%d",&n);
    product=1;
    for(i=1;i<=n;i++){
        product=product*i;
    }
    printf("product=%.0f
",product);

    return 0;
}

2.10

#include<stdio.h>
#include<math.h>
int main(void)
{
    int i,n;
    double power;

    printf("Enter n:");
    scanf("%d",&n);
    for(i=0;i<=n;i++){
        power=pow(2,i);
        printf("pow(2,%d)=%.0f
",i,power);
    }

    return 0;
}

2.11

#include<stdio.h>
double fact(int n);

int main(void)
{
    int i,n;
    double result;

    printf("Enter n:");
    scanf("%d",&n);
    for(i=0;i<=n;i++){
        result=fact(i);
        printf("%d!=%.0f
",i,result);
    }

    return 0;
}

double fact(int n)
{
    int i;
    double product;

    product=1;
    for(i=1;i<=n;i++){
        product=product*i;
    }

    return product;
}