Chapter 5 ：Operators，Expressions and Statements

1. Write a program that converts time in minutes to time in hours  and  minutes.  Use #define or const to create a  symbolic constant for 60. Use a while loop to allow the user to enter values repeatedly and terminate the loop if a value for the time of 0 or less is entered.

#include <stdio.h>

int main(void) {
    const int minperhour = 60;
    int minutes, hours, mins;
    printf("Enter the number of minutes to convert: ");
    scanf("%d", &minutes);
    while (minutes > 0) {
        hours = minutes / minperhour;
        mins = minutes % minperhour;
        printf("%d minutes = %d hours, %d minutes
", minutes, hours, mins);
        printf("Enter next minutes value (0 to quit): ");
        scanf("%d", &minutes);
    }
    printf("Bye
");
    return 0;
}

3. Write a program that asks the user to enter the number of days and then converts that value to weeks and days. For example, it would convert 18 days to 2 weeks, 4 days. Display results in the following format: 

18 days are 2 weeks, 4 days.

Use a while loop to allow the user to repeatedly enter day values; terminate the loop when the user enters a nonpositive value, such as 0 or -20.

#include <stdio.h>

int main(void) {
    const int daysperweek = 7;
    int days, weeks, day_rem;
    printf("Enter the number of days: ");
    scanf("%d", &days);
    while (days > 0) {
        weeks = days / daysperweek;
        day_rem = days % daysperweek;
        printf("%d days are %d weeks and %d days.
", days, weeks, day_rem);
        printf("Enter the number of days (0 or less to end): ");

        scanf("%d", &days);
    }
    printf("Done!
");
    return 0;
}

---

5. Write a program that requests a type double number and prints the value of the number cubed. Use a function of your own design to cube the value and print it. The main() program should pass the entered value to this function.

#include <stdio.h>

void showCube(double x);

int main(void) {
    double val;
    printf("Enter a floating-point value: ");
    scanf("%lf", &val);
    showCube(val);
    return 0;
}

void showCube(double x) {
    printf("The cube of %e is %e.
", x, x * x * x);
}