第四章编程练习

*4-2

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

int main(int argc, char const *argv[])
{
    char name[10];
    printf("give me your name：");
    scanf("%s", name );
    printf("\"%s\"\n", name);
    printf("\"%18s\"\n", name);
    printf("\"%-18s\"\n", name);
    int b = strlen(name) + 3;
    printf("\"%*s\"\n", b, name);

    return 0;
}

/* 
give me your name：elon
"elon"
"              elon"
"elon              "
"   elon"
*/

 *4-3

#include <stdio.h>

int main(int argc, char const *argv[])
{
    float a;
    printf("give me a float number：");
    scanf("%f", &a);
    printf("The input is %.1f or %.1e.\n", a, a);
    printf("The input is %+.3f or %.3E.\n", a, a);

    return 0;
}

/* 
give me a float number：21.29
The input is 21.3 or 2.1e+001.
The input is +21.290 or 2.129E+001.
*/

4-4

#include <stdio.h>

int main(int argc, char const *argv[])
{
    float a;
    char name[20];
    printf("give me your height(inches)：");
    scanf("%f", &a);
    printf("your name please:");
    scanf("%s", name);
    printf("%s, you are %.3f feet tall\n", name, a/12.0 );

    return 0;
}

/* 
give me your height(inches)：74.496
your name please:Dabney
Dabney, you are 6.208 feet tall
*/

*4-5

#include <stdio.h>

int main(int argc, char const *argv[])
{
    float speed, file_size, dtime;
    printf("Enter the download speed(Mb/s)：");
    scanf("%f", &speed);
    printf("Enter the size of file(MB)：");
    scanf("%f", &file_size);
    dtime = file_size * 8 / speed;
    printf("At %.2f megabits per second,a file of %.2f megabytes \
download in %.2f seconds.\n", speed, file_size, dtime );

    return 0;
}

/* 
Enter the download speed(Mb/s)：18.12
Enter the size of file(MB)：2.20
At 18.12 megabits per second,a file of 2.20 megabytes download in 0.97 seconds.
*/

*4-6

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

int main(int argc, char const *argv[])
{
    char fname[20];
    char lname[20];
    printf("Enter your first name：");
    scanf("%s", fname);
    printf("Enter your last name：");
    scanf("%s", lname);
    int fname_len = strlen(fname);
    int lname_len = strlen(lname);
    printf("%s %s\n", fname, lname );
    printf("%*d %*d\n", fname_len, fname_len, lname_len, lname_len );
    printf("%s %s\n", fname, lname );
    printf("%-*d %-*d\n", fname_len, fname_len, lname_len, lname_len );

    return 0;
}

/* 
Enter your first name：Melissa
Enter your last name：Honeybee
Melissa Honeybee
      7        8
Melissa Honeybee
7       8

*/

4-7

 

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

int main(int argc, char const *argv[])
{
    float f = 1.0/3.0;
    double d = 1.0/3.0;

    printf("%.6f\n", f );
    printf("%.12f\n", f );
    printf("%.16f\n", f );
    printf("%.6f\n", d );
    printf("%.12f\n", d );
    printf("%.16f\n", d );
    printf("FLT_DIG:%d\n", FLT_DIG);
    printf("DBL_DIG:%d\n", DBL_DIG);

    return 0;
}

/* 
0.333333
0.333333343267
0.3333333432674408
0.333333
0.333333333333
0.3333333333333333
FLT_DIG:6
DBL_DIG:15

*/