Guidelines for HW 5: You are encouraged to work teams of two or three (not more than three) for this assignment, although individual submissions will be accepted. When you program as a team, you should work together, using the style of pair programming (http://www.pairprogramming.com), as demonstrated in lecture. If you work in teams then the names of all the students must appear in the program.

Your name must appear at the top of the program in comments, such as:

/************************************************************/
/* Authors:   Amy Apon and Brent Hollosi                    */
/* Filename:  Vending.c                                     */
/*                                                          */
/* This program implements the functions of a vending       */
/* machine. The machine sells three items:  A sweet roll    */
/* for $.85, a candy bar for $.75, and gum for $.45.        */
/*                                                          */
/* A customer is asked to select an item.  After selecting  */
/* an item, the program receives coins ($.05, $.10 or $.25) */
/* from the customer until either the amount of money is    */
/* greater than the cost of the item, or the customer       */
/* selects quit.                                            */
/*                                                          */
/* At the end, the program prints the item purchased, if    */
/* any, and the amount of change, if any.                   */
/************************************************************/

Assignment Part One: [60 points] This assignment is to implement the functionality of a vending machine. The vending machine sells three items: A sweet roll for $.85, a candy bar for $.75, and gum for $.45. A customer is asked to select an item. After selecting an item, the program receives coins ($.05, $.10 or $.25) from the customer until either the amount of money is greater than the cost of the item, or the customer selects cancel. At the end, the program prints the item purchased, if any, and the amount of change, if any.

You will use a switch statement and functions to implement this program.

For interactive execution the screen dialogue should appear similar to this:

aapon@turing:~ $ ./Vending
Welcome to the Vending Machine!  What would you like to buy?

Items:  
   Sweet Roll: $0.85
   Candy Bar:  $0.75
   Gum:        $0.45

Enter an item, or q to quit (s=sweet roll, c=candy bar, g=gum, q=quit): s

You have selected Sweet Roll.  

Enter coins or q to quit (1=nickle, 2=dime, 3=quarter, q=quit):  3

You have entered $0.25.
Enter coins or q to quit (1=nickle, 2=dime, 3=quarter, q=quit):  3

You have entered $0.50
Enter coins or q to quit (1=nickle, 2=dime, 3=quarter, q=quit):  3

You have entered $0.75
Enter coins or q to quit (1=nickle, 2=dime, 3=quarter, q=quit):  3

You have entered $1.00

You have purchased a Sweet Roll.

Your change is $0.15.

Have a Nice Day!

You may use the following pseudocode for the main program:

int main() {
  define variables:  char itemtype, ...
  print welcome message and prompt
  itemtype = getchar();
  switch (itemtype) {
      case 's': print message
                retval = getcoins(85);
                break;
      case 'c': print message
                retval = getcoins(75);
                break;
      case 'g': print message
                retval = getcoins(45);
                break;
      default:  print message
  }
  if (retval < 0) printf("No product purchased!\n");
  else print amount of change
  print Have a Nice Day!
}

int getcoins(int cost);

The getcoins function returns a -1 if the quit is selected. Otherwise it returns the amount of change that is to be returned to the customer. The amount of change is the value of the coins minus the cost of the purchase. You do not need to specify the exact coins that are returned, but you may get extra credit for this and other extra functionality.

You may use the following pseudocode to help you get started on the getcoins function:

    define variables

    print prompt, Enter coins or q to quit (1=nickle, 2=dime, 3=quarter, q=quit): 
    coin = getchar();   
    calculate value

    while coin is not quit and value is less than amount {
       print prompt, Enter coins or q to quit (1=nickle, 2=dime, 3=quarter, q=quit): 
       coin = getchar();   
       calculate value
    } /* end while */
    if (coin == 'q') return(-1);
    else return the amount of the change

In your HW5 directory, place the five example execution traces, as plain text files, similar to that shown above.

For fun: As described the vending machine dispenses a sweet roll, a candy bar, and gun, and accepts U.S. money. If you like you may change the items to something else (e.g., an epic sword, bronze armour, a fish), and you may use another type of money (e.g., gold coins) as long as the monetary units (5, 10 25) and the items costs (85, 75, 45) stay the same.

Grading: Grades on this program will be assigned using these guidelines:

• A program that does not compile but has the appearance of a correct program will receive 15 points.
• A program that compiles and has the appearance of a correct program, but fails to execute close to the expected output will receive 20 points.
• If your program compiles and executes, then you will gain points as follows:
  • Correct implementation of switch and main code: 5 points
  • Correct implementation of function header and parameters for getcoins: 5 points
  • Correct implementation of getcoins function, including the calculation of the value of the coins: 15 points
  • Good formatting, indenting, selection of variable names, and comments where appropriate: 5 points
  • Good test cases that cover the necessary testing of the program: 10 points
  • Up to 3 points extra credit may be awarded to programs that display extra ingenuity or functionality in the solution. For example, you may wish to handle invalid entries.

Grading: Grades on this program will be assigned using these guidelines:

• A program that does not compile but has the appearance of a correct program will receive 12 points.
• A program that compiles and has the appearance of a correct program, but fails to execute close to the expected output will receive 15 points.
• If your program compiles and executes, then you will gain points as follows:
  • Correct generation of random number between 1 and 1000: 5 points
  • Correct implementation of main code, inner loop, and high/low test: 10 points
  • Correct implementation of outer loop to play again: 5 points
  • Good formatting, indenting, selection of variable names, and comments where appropriate: 5 points

What you turn in: Each student must submit a separate program using the submit utility on turing. Do these steps:

1. Write your program in a subdirectory of your home directory called hw5, as described above.
2. Submit your program on turing. That is, from the hw5 subdirectory:

Enjoy!