C primer plus 编程练习 4.8

1.

#include <stdio.h>
#include <string.h>
int main(void)
{
	char name[40];
	unsigned width;
	printf("Please enter your name:\n");
	scanf("%s",name);
	width = strlen(name) + 3;
	printf("\"%s\"\n",name);
        printf("\"%20s\"\n",name);
	printf("\"%-20s\"\n",name);
	printf("\"%*s\"\n",width,name);

	return 0;
}

3.

#include <stdio.h>

int main(void)
{
	float num;
	printf("Please input a number:\n");
	scanf("%f",&num);
	printf("The input is %2.1f or %1.1e",num,num);
	printf("The input is %+2.3f or %1.3e",num,num);


	return 0;
}

4.

#include <stdio.h>

int main(void)
{
	char name[20];
	float height;

	printf("Please enter your name and heidgh(cm):\n");
	scanf("%s%f",name,&height);
	printf("%s,you are %1.3f m feet tall",name,height/100);

	return 0;
}

5.

#include <stdio.h>

int main(void)
{
	float speed;
	float space;
	float time;

	printf("Please enter downloads speed: Mb/s\n");
	scanf("%f",&speed);
        printf("Please enter files space: MB\n");
        scanf("%f",&space);
	printf("At %2.2f megabits per second, a file of %1.2f megabytes\n",speed,space);
	time = space * 8 / speed;
	printf("downloads in %1.2f seconds",time);

	return 0;
}

6.

#include <stdio.h>
#include <string.h>

int main(void)
{
	char secname[20];
	char firname[20];
	printf("Please enter your secnd name:\n");
        scanf("%s",secname);
	printf("Please enter your first name:\n");
	scanf("%s",firname);
	printf("your name is: %s %s\n",firname,secname);
	printf("%s %s\n",firname,secname);
	printf("%-*d %-*d\n",strlen(firname),strlen(firname),strlen(secname),strlen(secname));
	printf("%s %s\n",firname,secname);
        printf("%*d %*d\n",strlen(firname),strlen(firname),strlen(secname),strlen(secname));

	return 0;
}

7.

#include <stdio.h>
#include <float.h>
int main(void)
{
	double var1 = 1.0 / 3.0;
	float var2 = 1.0 / 3.0;
	printf("float values: ");
	printf("%0.6f,%0.12f,%0.16f\n",var1,var1,var1);
	printf("double values: ");
	printf("%0.6f,%0.12f,%0.16f\n",var2,var2,var2);
	printf("FLT_DIG: %d\n",FLT_DIG);
        printf("DBL_DIG: %d\n",DBL_DIG);
	return 0;
}

8.

#include <stdio.h>
#define LITRE_PER_GALLON 3.785
#define KM_PER_MILE 1.609

int main(void)
{
	float drive_distance = 0.0;
	float oil_consumption = 0.0;

        printf("Please enter the drive distance(mi): \n");
	scanf("%f",&drive_distance);
	getchar();

	printf("Please enter the oil consumption(gallon):\n");
	scanf("%f",&oil_consumption);
	getchar();

	printf("The distance of per-fuel is: %.1f ml/gallon\n",drive_distance / oil_consumption);
	printf("The fuel of per-distace: %.1f L/100 km\n",
		    LITRE_PER_GALLON * oil_consumption / (KM_PER_MILE * drive_distance) * 100);

	return 0;
}