2

#include <stdio.h>

int main(void)
{
  char name[40];

  printf("请输入你的姓名: ");
  scanf("%s", name);
  printf("\"%s\"\n", name);
  printf("\"%20s\"\n", name);
  printf("\"%-20s\"\n", name);
  printf("\"%s   \"\n", name);

  getchar();
  getchar();
  return 0;
}

3

#include <stdio.h>
#define X 21.29

int main(void)
{
  printf("%+.3f %.3e\n", X, X);

  getchar();
  return 0;
}

 

4

#include <stdio.h>

int main(void)
{
  char name[40];
  float h;

  printf("请输入你姓名: ");
  scanf("%s", name);
  printf("请输入你的身高[cm]: ");
  scanf("%f", &h);
  printf("%s, 你有 %.3f m 感觉挺高的. \n", name, h / 100);

  getchar();
  getchar();
  return 0;
}

 

5

#include <stdio.h>

int main(void)
{
  float a, b, c;

  printf("文件下载速度计算工具\n\n");
  printf("请输入你的网速[Mb/s]: ");
  scanf_s("%f", &a);
  printf("请输入下载文件的大小[MB]: ");
  scanf_s("%f", &b);
  c = b / a;
  printf("你的网速 %.2f Mb/s 下载一个 %.2f MB 的文件 \n", a, b);
  printf("需要 %.2f s \n", c);

  getchar();
  getchar();
  return 0;
}

 

6

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

int main(void)
{
  char name[20], name2[20];
  
  printf("请输入你的姓: ");
  scanf("%s", name);
  printf("请输入你的名: ");
  scanf("%s", name2);
  printf("%*s %*s\n", strlen(name), name, strlen(name2), name2);
  printf("%*d %*d\n", strlen(name), strlen(name), strlen(name2), strlen(name2));

  getchar();
  getchar();
  return 0;
}

 

7

#include <stdio.h>
#include <float.h>

int main()
{
  double x = 1.0/3.0;
  float y = 1.0/3.0;

  printf("double\n%.6f %.12f %.16f\n", x, x, x);
  printf("float\n%.6f %.12f %.16f\n", y, y, y);
  printf("double类型最少有效数字位数:%d \nfloat类型最少有效数字位数:%d\n", DBL_DIG, FLT_DIG);

  getchar();
  return 0;

}

 

8

#include <stdio.h>
#define A 1.609344
#define B 3.785

int main()
{
  float x, y, c, d, e;

  printf("请输入旅行的里程[Km]: ");
  scanf_s("%f", &x);
  printf("请输入消耗的汽油量[L]: ");
  scanf_s("%f", &y);
  c = x / y;
  d = c * B;
  e = d / A;
  
  printf("汽车每耗油 1L 行驶 %.1fKm \n", c);
  printf("消耗每加仑汽油行驶了 %.1f 英里. \n", e);
  printf("每100公里消耗汽油: %.1fL \n", 100 / c);

  getchar();
  getchar();
  return 0;
}