Circle Calculations

CIS 2003 - Introduction to C++ and C Programming
Bob Comer, Professor, CIS/CSC

Assignment 2 - Circle Calculations

Read through Chapter 2 in your textbook before starting this assignment.

Write a C++ program that will calculate and print the diameter, circumference, or area of a circle depending on a command entered by the user. The commands are:

D - calculate and print the diameter of a circle
C - calculate and print the circumference of a circle
A - calculate and print the area of a circle with radius
E - end the program

If the user enters 'D', 'C', or 'A', your program should input a radius for the circle from the user. Your program should have a loop to allow multiple calculations.

Formulas and constants

     diameter = 2 x radius
     circumference = 2 x pi x radius
     area = pi x radius x radius
     use 3.14159 for pi

Error Checking

Your program should check for invalid commands. If the user enters a command other than 'D', 'C', 'A', or 'E', print an appropriate error message and continue with the next command.

Sample Program Dialog

Your screen dialog should look similar to this (user input is shown in bold). You should format your output to display 2 digits to the right of the decimal point for all floating-point numbers.

Circle Calculations Program

Commands:
   D - print circle diameter
   C - print circle circumference
   A - print circle area
   E - end the program

Enter a command: C
Enter circle radius:1.5
A circle with radius 1.50 has circumference 9.42.

Enter a command: D
Enter circle radius: 2
A circle with radius 2.00 has diameter 4.00.

Enter a command: E

Program Notes/Hints

Use a sentinel-controlled loop.

When the user types a line of input and presses the enter key, the entire line of input, including a newline chacter that is generated when the enter key is pressed, is passed to the program. Two common ways of inputting character data from a line are the get() function and the extractor operator. The get() function has the ability to input any character, including spaces, newline characters, and tabs. (The space, newline, and tab characters are called whitespace characters.) When you are interested in reading only non-whitespace characters, the extractor operator is often a better choice.

Here is a quick explanation of how they work:

The following code:

int ch;
ch = cin.get();

will read the very next character from the keyboard and store it in integer variable ch. The next character could be a space, tab, or newline character. It could even be a newline character that was not read by the previous input statement.

The following code:

char ch;
cin >> ch;

will skip over (read and discard) any leading whitespace characters and then read and store the next (non-whitespace) character in variable ch.

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