C Primer Plus第六版第四章复习答案

1. 再次运行程序，输入David mk结果如下图
   由于使用%s读取用户输入，scanf读取到David mk中间的空格处停止，所以name中只接收到了David， 空格停留在输入中，接下来%f也不会读取空格，所以weight没得到数据，执行结果和将scanf("%f", &weight);注释掉的结果是相同的

2. a. He sold the painting for $234.50.

   b. Hi!

   c. His Hamlet was funny without being vulgar.
   has 42 characters.

   d. Is 1.20e+003 the same as 1201.00?

3. 答案1：#define Q ““His Hamlet was funny without being vulgar.”” 答案二,在打印字符串Q的前后加上转换说明/"： printf("\"%s\"\n has %d characters. \n", Q, strlen(Q));

4. 修改后的程序如下：

#include <stdio.h>
#define B "booboo"
#define X 10
int main(void)
{
	int age, xp ;
	char name[40];
	
	printf("Please enter your first name. \n");
	scanf("%s", name);
	printf("All right, %s, what's your age?\n", name);
	scanf("%d", &age);
	xp = age + X;
	printf("That's a %s! You must be at least %d.\n", B, xp);
		
	return 0;
}

printf("This copy of \"%s\" sells for $%.2f.\n", BOOK, cost);
printf("That is %.0f%% of list.", percent);

6.  a. %d
    b. %4X
    c. %10.3f
    d. %12.2e
    e. %-30s
   

7. a. %15lu
   b. %#4x
   c. %-12.2E
   d. %+10.3f
   e. %8.8s

8. a. %6.4d
   

   b. %*o
   c. %2c
   d. %+.2f
   e. %-7.5s

9. a. `int a;  scanf("%d", &a);`
   

   b. double d; scanf("%e", &d);
   c. char array[40]; scanf("%s", array);
   d. char array1[40]; int a1; scanf("%s %d", array1, &a1);
   e. char array2[40]; int a2; scanf("%*s %d", &a2);
10. what is whitespace? space tablet enter 空格 制表符 回车符,补充：C语言使用空白分隔几号，scanf使用空白分隔连续的输入项
11. %只是修饰符，修改后的语句为， printf("The double type is %zd bytes..\n", sizeof(double));
12. 当然不行了
    编译时会报错，如下图所示：