CS 16, Summer 2012
Programming Project 2

Due: Friday, August 10, 11:59pm
Worth: 5% of final grade

1. Write a C program to print diamond shapes composed of '*' characters like this example, and as further specified below.

   Here the user asks for a diamond of size 5, and then no more diamonds (user input is boldface).

   -bash-4.2$ ./diamond enter ODD size > 0: 5 * *** ***** *** * more? n -bash-4.2$

   • The source code file must be named diamond.c and we suggest you create a directory named ~/cs16/p2 to store it in. Type your name and the date in a comment at the start of the file.
   • For full credit, the program must behave and produce results exactly like our solution. You can run that solution from your CSIL account as follows:
     
     ~kyledewey/cs16/p2/diamond
     Notice especially:
     (a) The program keeps printing diamonds as long as the user answers Y or y to the "more?" question, but quits if the user enters anything else.
     (b) The program makes certain that the user enters an odd, positive number in response to the size question. If anything else is entered, the program does not draw a diamond and does not exit or endlessly loop, but instead it calmly informs the user about the mistake and prompts for the size again.
     Here is a longer sample run that demonstrates the proper behavior. [Be sure to read the notes too.]
   • We highly recommend that you do not try to solve all of the problems at once! Partial credit will be available. Here is a sensible order to solve the various problems:
     (a) Work on the diamond shape first, without worrying about the "more?" and error checking problems. And don't even try to solve the whole diamond at once - maybe start with the top left half, then the top right, and then the bottom half.
     (b) Work on the "more?" problem - to print as many diamonds as the user wants.
     (c) Work on the user input checking problems. Print error messages when the user enters a non-number or a non-odd number greater than zero - exactly like the solution does.
   • Remember: functions are your friends, and they can serve as mechanisms to break your code up into different subproblems. Our solution defined nine functions, but you can use as many or as few as you want.
   • Hint (and a gift): our solution found it necessary to "flush" the input stream in order to properly handle user input (especially in the case of faulty input). We used the following function two times (but an alternative solution called it three times!), and you may copy/paste and use it in your solution if you want:

     /* utility function flushes input buffer */
     void flush(void) {
         while (getchar() != '\n')
             ;
     }

2. Compile the program and thoroughly test it at CSIL. Make sure the version that you turn in will successfully compile and execute, so we will be able to test it too. Remember that partial credit will be awarded for partial solutions - but only if we can test your solution. That means you should only turn in working code, and remove (or completely "comment out") any failed attempts to solve the more advanced problems. If we cannot compile and test your program, then we cannot award more than minimal credit for your efforts.
3. Go to CSIL (in person unless you can manage this step remotely without any assistance from us). Open a terminal window, cd to the same directory as your source code file, then type the following:
   
   turnin p2@cs16 diamond.c
   

Optional Challenges

Do not change diamond.c to accomplish these challenges. Write new programs instead. Do not turn in these challenges - they are just for you to practice and learn. By the way, this part doesn't count, and so it is okay to work with a partner on it.

• Allow the user to select the character to print (instead of just always '*').
• If you did the previous challenge, then modify it to verify that the user enters one of the printable characters. See the table of ASCII codes in the text's Appendix B.
• Try printing two (or more) diamonds side-by-side like this:

    *     *
   ***   ***
  ***** *****
   ***   ***
    *     *

• Write programs to print other shapes and combinations. For example, here are four different triangles side-by-side:

  *      ****** ******      *
  **     *****   *****     **
  ***    ****     ****    ***
  ****   ***       ***   ****
  *****  **         **  *****
  ****** *           * ******

• If you have the textbook, try any of the programming problems at the end of Etter chapters 3 and 4, pp. 142-147 and 200-205.

Adapted by Kyle Dewey from C. Michael Costanzo