Introduction
============
You've been working very hard! In this lab, we will step back a
little and work through some examples of using file streams and
objects. Not to worry though, I promise this will still be a
challenging and rewarding lead in to the next leg of the journey!
Lab 6.1 (Guided) Selling more than 3 things
============================================
The owners of Trillium Inc. have decided to replace their old cash
register system. Their old system was severely limited, so they are
a bit wary of programmers. Also, their cashiers have complained
that the old system is too complicated to use. They want something
simple and menu driven. Finally, the owners have decided that it
would be nice if the cash register could keep a record of its
transactions. You know, that way they can track sales and make sure
they have the right amount of money on hand.
For the first part of this, we are going to create a simple menu
system for the register. It will have 2 modes, transaction entry
and journal review. We will be storing the cash register history in
a file. The first step is to produce a stub of this program in
order to test out the menu system. Enter and execute the following
code, come back when you have it running.
Notice how all the above functions are stubs. This allows us to
test the program and see what functions are getting executed. The
next step is to implement the cashier's interface. What the
cashiers have decided is that they want to enter an item, the
quantity of the item, and its cost. They want to repeat this until
they enter a blank item. Then they want a simple display indicating
the total amount due on the receipt. Also, if we keep in mind that
we want to write all this to a journal, we can go ahead and call our
writeLineItem function as well as our endTransaction function.
We do all this in the newTransaction function. Modify
newTransaction so that it reads as follows:
void
newTransaction() {
string item;
int qty;
double cost;
double total = 0.0;
//go until we get an empty item
do {
//clear out cin
cin.clear(); cin.ignore(1000, '\n');
//mark the end of the transaction
endTransaction();
}
Test your program again to make sure it is working.
We now turn our attention to the journal file. We have to declare
the format that we are going to store transactions in. Because item
names can contain spaces, we will put each field on a line by
itself. Thus the format goes:
item name
quantity
cost
With a blank line separating transactions. Because we are
journaling, we want to open the file in append mode. The two key
operations are "writeLineItem" and "endTransaction". Modify these
two functions so they read as below:
//append a single item to the file, one field at a time
file.open("registerTape", ios::app);
file << item << endl;
file << qty << endl;
file << cost << endl;
file.close();
}
//append a single blank line to the file. This ends the transaction.
file.open("registerTape", ios::app);
file << endl;
file.close();
}
Test this program out now. Note that it creates a file named
"registerTape" in your directory. cat registerTape and verify that
this writes the correct format. You should enter a few transactions
using your program to test it.
Now we only need to provide a way of running the reports. To do
this, we start with the following modification:
void
readReceipts() {
ifstream file; //the journal file;
string item;
int qty;
double cost, lineCost;
double total = 0.0;
//open the file and read to the end
file.open("registerTape");
while(!file.eof()) {
//get the item
getline(file, item);
//handle break in transactions
if(!item.length()){
//display the transaction total and reset
if(total > 0)
cout << setw(32) << total << endl << endl;
total = 0.0;
continue;
}
Run your program a few times, enter some transactions, and verify
that they show up in the reports.
Now as a final exercise, cleanup the output of readReceipts to make
it look better. Add some headers and some dollar signs. This is a
subjective thing, so I want you to be creative. Have fun practicing
your formatting skills and make a display you can be proud of.
When you are done, create a script file containing your complete
code, your run, and a cat of your registerTape file.
Lab 6.2 Computing Your Grade
=============================
Imagine, for a moment, that you are in a CS class who's final grade
is computed by means of weighted averages divided into the following
categories:
Given your present circumstances, you shouldn't have to tax your
imagination too heavily! Now, suppose that you want to keep track
of your grade. A great way to do this would be with a program which
keeps records in a file. Since that is the topic of this lab, I
think you can see where we are headed!
So now, here's your task. You want to design and implement a
program which does the following:
1. Presents the user with the choice of entering a new grade or
reviewing old grades.
2. Stores the grades in a single file.
3. Shows a grade report listing all of your scores (along with the
category of each) and displays the averages for each category,
and the weighted final average.
The design of the interface and the file are completely up to you
this time! Be sure to include a description of your file format in
the pseudocode. Also, include examples of what your user interface
will look like.
HINTS:
- enum is your friend. There are only so many categories.
- You can use a similar strategy to that which was developed in the
guided part of lab 6.
