c primer plus 4编程练习

1、编写一个程序，提示用户输入名和姓， 然后以“名，姓”的格式打印出来。

#include <stdio.h>

int main(void)
{
    char name[128];
    char surname[128];
    
    printf("please input your name: "); 
    scanf("%s", name);
    
    printf("please input your surname: ");
    scanf("%s", surname);
    
    printf("your whole name: %s,%s.
", name, surname);
    
    return 0;
}

2、编写一个程序，提示用户输入名字，并执行以下操作：

a、打印名字，包括双引号

#include <stdio.h>

int main(void)
{
    char name[128];
    
    printf("please input your name: ");
    scanf("%s", name);
    
    printf("your name: "%s"
", name);
    
    return 0;
}

b、在宽度为20的字段右端打印名字，包括双引号：

#include <stdio.h>

int main(void)
{
    char name[128];
    
    printf("please input your name: ");
    scanf("%s", name);
    
    printf("your name: "%20s"
", name);
    
    return 0;
}

c、在宽度为20的字段右端打印名字，包括双引号：

#include <stdio.h>

int main(void)
{
    char name[128];
    
    printf("please input your name: ");
    scanf("%s", name);
    
    printf("your name: "%20s"
", name);
    
    return 0;
}

d、在比姓名宽度宽3的字段中打印名字

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

int main(void)
{
    char name[128];
    int namelen;
    
    printf("please input your name: ");
    scanf("%s", name);
    
    namelen = strlen(name) + 3;
    
    printf("your name: "%*s"
", namelen, name);
    
    return 0;
}

3、编写程序，读取一个浮点数，首先以小数点计数法打印，然后以指数计数法打印。 用下面的格式进行输出（系统不同，指数计数法显示的位数可能不同）：

a. input is 21.3 or 2.1e+001.

#include <stdio.h>

int main(void)
{
    float num;
    
    printf("please input an float: ");
    scanf("%f", &num);
    
    printf("The input is %.1f or %.1e.
", num, num);
    
    return 0;
}

b. The input is +21.290 or 2.129E+001.

#include <stdio.h>

int main(void)
{
    float num;
    
    printf("please input an float: ");
    scanf("%f", &num);
    
    printf("The input is %+.3f or %.3E.
", num, num);
    
    return 0;
}

4、编写一个程序，提示用户输入身高（单位：英寸）和姓名，然后以下面的格式显示用户当输入的信息：

Dabey，you are 6.208feet tall。

#include <stdio.h>

int main(void)
{
    float  height;
    
    printf("please input your height in inch:");
    scanf("%f", &height);
    
    printf("Dabney, you are %.3f feet tall.
", height / 12);
    
    return 0;
}

5、……

#include <stdio.h>

int main(void)
{
    float netspeed, filesize, time;
    
    printf("please input the netspeed: ");
    scanf("%f", &netspeed);
    
    printf("please input the filesize: ");
    scanf("%f", &filesize);
    
    time = filesize * 8 / netspeed;
    
    printf("download im %.2f second.
", time);
    
    return 0;
}

6、……

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

int main(void)
{
    char name[128];
    char surname[128];
    
    int namelen;
    int surnamelen;
    
    printf("please input your name: ");
    scanf("%s", name);
    
    printf("please input your surname: ");
    scanf("%s", surname);
    
    namelen = strlen(name);
    surnamelen = strlen(surname);
    
    printf("%s %s
", name, surname);
    printf("%*d %*d

", namelen, namelen, surnamelen, surnamelen);
    
    printf("%s %s
", name, surname);
    printf("%-*d %-*d

", namelen, namelen, surnamelen, surnamelen);
    
    return 0;
}

 7、……

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

int main(void)
{
    double num1 = 1.0/3.0;
    float  num2 = 1.0/3.0;
    
    printf("time1 num1: %.6f.
",  num1);
    printf("time2 num1: %.12f.
", num1);
    printf("time3 num1: %.16f.

", num1);
    
    printf("time1 num2: %.6f.
", num2);
    printf("time2 num2: %.12f.
", num2);
    printf("time3 num2: %.16f.

", num2);
    
    printf("FLT_DIG: %d.
", FLT_DIG);
    printf("DBL_DIG: %d.
", DBL_DIG);
    
    return 0;
}

8、……