Chapter 5 Solutions to exercises from the book C Primer Plus by Stephen Prata

Exercise 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.

Exercise 2:

Write a program that asks for an integer and then prints all the integers from
(and including) that value up to (and including) a value larger by 10. (That
is, if the input is 5, the output runs from 5 to 15.) Be sure to separate each
output value by a space or tab or newline.

Exercise 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.

Exercise 4:

Write a program that asks the user to enter a height in centimeters and then
displays the height in centimeters and in feet and inches. Fractional
centimeters and inches should be allowed, and the program should allow the
user to continue entering heights until a nonpositive value is entered. A
sample run should look like this:

Enter a height in centimeters: 182
182.0 cm = 5 feet, 11.7 inches
Enter a height in centimeters (<=0 to quit): 168.7
168.0 cm = 5 feet, 6.4 inches
Enter a height in centimeters (<=0 to quit): 0

Exercise 5:

Change the program addemup.c (Listing 5.13), which found the sum of the first 20
integers. (If you prefer, you can think of addemup.c as a program that calculates
how much money you get in 20 days if you receive $1 the first day, $2 the second
day, $3 the third day, and so on.) Modify the program so that you can tell it
interactively how far the calculation should proceed. That is, replace the 20 with
a variable that is read in.

Exercise 6:

Now modify the program of Programming Exercise 5 so that it computes the sum of the squares of the integers. (If you prefer, how much money you receive if you
get $1 the first day, $4 the second day, $9 the third day, and so on. This looks
like a much better deal!) C doesn’t have a squaring function, but you can use the
fact that the square of n is n * n.

Exercise 7:
 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.

Exercise 8:

 Write a program that displays the results of applying the modulus operation. The

 user should first enter an integer to be used as the second operand, which will

 then remain unchanged. Then the user enters the numbers for which the modulus

 will be computed, terminating the process by entering 0 or less. A sample run

 should look like this:


     This program computes moduli.

     Enter an integer to serve as the second operand: 256

     Now enter the first operand: 438

     438 % 256 is 182

     Enter next number for first operand (<= 0 to quit): 1234567

     1234567 % 256 is 135

     Enter next number for first operand (<= 0 to quit): 0


Exercise 9:

 Write a program that requests the user to enter a Fahrenheit temperature. The

 program should read the temperature as a type double number and pass it as an

 argument to a user-supplied function called Temperatures(). This function should

 calculate the Celsius equivalent and the Kelvin equivalent and display all three

 temperatures with a precision of two places to the right of the decimal. It

 should identify each value with the temperature scale it represents. Here is the

 formula for converting Fahrenheit to Celsius:

     Celsius = 5.0 / 9.0 * (Fahrenheit - 32.0)

 The Kelvin scale, commonly used in science, is a scale in which 0 represents

 absolute zero, the lower limit to possible temperatures. Here is the formula for

 converting Celsius to Kelvin:

     Kelvin = Celsius + 273.16

 The Temperatures() function should use const to create symbolic representations

 of the three constants that appear in the conversions. The main() function

 should use a loop to allow the user to enter temperatures repeatedly, stopping

 when a q or other nonnumeric value is entered. Use the fact that scanf() returns

 the number of items read, so it will return 1 if it reads a number, but it won’t

 return 1 if the user enters q. The == operator tests for equality, so you can

 use it to compare the return value of scanf() with 1.
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