第三章1

#include<stdio.h>
int main(void)
{
	int mynumber=38;
	int yournumber;

	printf("Input your number:");
	scanf("%d",&yournumber);
	if(yournumber==mynumber)
	   printf("OK!you are right!\n");
    else
       if(yournumber>mynumber)
		   printf("Sorry!your number is bigger than my number!\n");
	   else
	       printf("Sorry!your number is smaller than my number!\n");
	
	return 0;
}

　　

#include<stdio.h>
int main(void)
{
	int number;

	printf("Enter a number:");
	scanf("%d",&number);
	if(number%2==0){
		printf("The number is even.\n");
	}
	else{
		printf("The number is odd.\n");
	}

	return 0;
}

　　

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

	printf("Enter n:");
	scanf("%d",&n);
	total=0;
	count=0;
	for(i=1;i<=n;i++){
		printf("Enter grade#%d:",i);
		scanf("%lf",&grade);
		total=total+grade;
		if(grade<60){
			count++;
		}
	}
	printf("Grade average=%.2f\n",total/n);
	printf("Number of failures=%d\n",count);

	return 0;
}

　　

#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\n",x,y);

	return 0;
}

　　

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

	return 0;
}

　　

#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\n",letter,digit,other);

	return 0;
}

　　

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

	for(i=1;i<=5;i++){
		printf("[1]Select crisps\n");
		printf("[2]Select popcorn\n");
		printf("[3]Select chocolate\n");
		printf("[4]Select cola \n");
		printf("[0]exit \n");

		printf("Enter choice:");
		scanf("%d",&choice);
		if(choice==0)
			break;
		switch(choice){
		case 1:price=3.0;break;
		case 2:price=2.5;break;
		case 3:price=4.0;break;
		case 4:price=3.5;break;
		case 5:price=0.0;break;
		}
		printf("price=%0.1f\n",price);
	}
	printf("Thanks\n");

	return 0;
}

　　

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

	printf("Type in an expression:");
	scanf("%lf%c%lf",&value1,&op,&value2);
	switch(op){
	case'+':
		printf("=%.2f\n",value1+value2);
		break;
	case'-':
		printf("=.2f\n",value1-value2);
		break;
	case'*':
		printf("=.2f\n",value1*value2);
		break;
	case'/':
		printf("=.2f\n",value1/value2);
		break;
	default:
		printf("Unknown operator\n");
		break;
	}

	return 0;
}

　　

#include<stdio.h>
int main(void)
{
	int blank,digit,other;
	char ch;
	int i;
	blank=digit=other=0;
	printf("Enter 10 characters:");
	for(i=1;i<=10;i++){
		ch=getchar();
		switch(ch){
		case' ':

		case'\n':
			blank ++;
			break;
			case'0':case'1':case'2':case'3':case'4':
			case'5':case'6':case'7':case'8':case'9':
				digit ++;
				break;
			default:
				other ++; 
				break;
		}
	}
	printf("blank=%d,digit=%d,other=%d\n",blank,digit,other);

	return 0;
}

　　

#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\n",value1+value2);
	else if(op=='-')
		printf("=%.2f\n",value1-value2);
	else if(op=='*')
		printf("=%.2f\n",value1*value2);
	else if(op=='/')
		if(value2!=0)
			printf("=%.2f\n",value1/value2);
		else
			printf("Divisor can not be 0!\n");
   	else
			printf("Unknown operator!\n");

	return 0;
}