第二章

2.1例2-1

/* 显示"Hello World!" */
# include<stdio.h>
int main(void)
{
    printf("Hello World!\n");

    return 0;
}

2.1例2-2

/* 显示"Hello World!" */
# include<stdio.h>
int main(void)
{
    printf("Hello World!\n");

    return 0;
}

2.2例2-3

/* 将华氏温度转换为摄氏温度 */
#include<stdio.h>
int main(void)
{
    /* 定义两个整型变量,celsius表示摄氏度,fahr表示华氏度 */
    int celsius,fahr;

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

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

    return 0;
}

2.3例2-4

/* 计算二分段函数 */
#include<stdio.h>
int main(void)
{
    double x,y;

    printf("Enter x(x>=0):\n");

    scanf("%lf",&x);

    if(x<=15){
        y=4*x/3;
    }
    else{
        y=2.5*x-10.5;
    }
    printf("y=f(%f)=%.2f\n",x,y);

    return 0;
}

2.3例2-5

/* 计算存款的利息 */
#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\n",sum);

    return 0;
}

2.4例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\n");

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

    return 0;
}

2.4例2-7

/* 计算1+2+3+…+n */
#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",n,sum);

    return 0;
}

2.4例2-8

/* 计算1-1/3+1/5-1/7+…共n项之和 */
#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\n",sum);

    return 0;
}

2.4例2-9

 

/* 输入一个正整数n,求n! */
#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\n",product);

    return 0;
}

 

2.5例2-10

/* 调用幂函数pow()生成乘方表 */
#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\n",i,power);
    }

    return 0;
}

2.5例2-11

/* 定义和调用求阶乘函数生成阶乘表 */
#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\n",i,result);
    }

    return 0;
}