第二章

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=5d,celsius=%d/n",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;
}

   #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.lf
",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;
}

#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;
}

#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;
}

#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;
}

#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;
}