Water Usage: design and program evolution

<body stylesrc="lab4e5comment.htm" bgcolor="#FFFFFF"> <p align="center"> </p> <p align="center"> </p> <table border="4" width="100%" height="60"> <tr> <th><h1><font size="5">CS 150 Introduction to C++ Programming - Spring 1998 </font></h1> </th> </tr> </table> <p align="center">[ <a href="http://www.cs.odu.edu/~cs150" target="_top">Home</a> |<a href="ftp://ftp.cs.odu.edu/pub/ray/150"> Lecture Notes</a>| <a href="http://www.cs.odu.edu/~wild/cs150">WebTutor</a> | <a href="http://www.cs.odu.edu/~wild/cs150/site.cgi" target="_top">WebTutor Site Map</a>]</p> <hr> <h2 align="center">Commentary on Incremental Design</h2> <p align="left">This frame contains commentary on the developing incremental design shown in the right frame.</p> <p align="left">It is also used to move through the developing design stages. You can always start over by <a href="lab4e5s0.htm" target="program">clicking here.</a></p> <p align="left">When you are ready, <a href="lab4e5s1.htm" target="program">click here to show the initial skeletal design.</a></p> <p align="left">WATER Step 1:</p> <p align="left">Basically this is the skeletal C++ program with comments indicating where certain parts of the C++ program should go.<br> We assume that (like most programs), there is an input, process, output structure.</p> <p>This program will compile and execute, but of course does nothing.</p> <p>Now let's give the specification for this case study: the Water Usage Problem</p> <table border="1"> <tr> <td>For planning purposes<strong> The Water Company</strong> wants to classify the water usage of their customers. The water company has two kinds of customers: Home users and Industrial Users.<br> <strong>INPUT STEP: </strong>This program takes as input<br> 1) the category of the customer ('H' or 'h' for home user and 'I' or 'i' for industrial user)<br> 2) the number of gallons consumed last billing period<br> <strong>PROCESS STEP:</strong>It classifies home users as "efficient" is they use less than 3500 gallons, or "abnormal" otherwise.<br> It classifies industrial users as "small" if they use less than 15000 gallons, "medium" if they use between 15000 and 30000 gallons and "large" otherwise<br> <strong>OUTPUT STEP: </strong>It then prints out the appropriate classification.</td> </tr> </table> <p>Let's start by refining the <strong>INPUT STEP</strong>.</p> <p><a href="lab4e5s2.htm" target="program">Click here for WATER step 2:</a></p> <p>(for this and subsequent versions, we will show the new part of the design in <font color="#FF0000"><strong>BOLD red letters</strong></font> and the <em>old part in italics</em>)<br> Since there are two input values, we will need two variables to store them.<br> Since the category of the customer is a single character, it is natural to choose the C++ <strong>char</strong> data type to remember this input. We decide to call this variable, <em>cat</em> (short for category).<br> Since the numbers of gallons is a whole number, we decide to store it in a C++ <strong>int</strong> data type called <em>gallon.</em></p> <p>Now we design the input part of the program. We decide to get the input from the keyboard, so we need to prompt the user so they know which input is being requested when.</p> <p>Notice for this refinement, we added only two C++ statements (the declarations of the variables <em>cat</em> and <em>gallon</em>. The rest of the refinement is still commentary. WHY? because at this stage we don't want to worry about getting the syntax of the C++ correct. We want to focus on solving the problem in English first, then we can worry about making it into legal C++ (in a later refinement). However, we did feel confident enough about declarations to put them directly into C++. And they should compile correctly even at this stage.</p> <p><a href="lab4e5s3.htm" target="program">Click here for WATER step 3:</a></p> <p>We decide to protect the program from typing mistakes by validating the input value and terminating the program if the user makes a mistake.<br> Notice how we use a selection statement ("if") to distinguish between valid and invalid input values. Again notice that this design is expressed as English comments statements with some C++ control stuff (The "if" part of the comment). Some programmers call this "<strong>Structured English</strong>" or <strong>pseudoCode.<br> </strong>Since it is a comment, we don't care how to compute"// if(gallon is ridiculous)", for instance. At this point, we should feel the design will get the job done and that we will eventually be able to translate the design into C++.</p> <form action="lab4e5.cgi" method="POST"> <p><font color="#FF0000">Forgetting about how to translate this into C++, does this design make sense to you? <br> <input type="radio" name="lab4e5q1" value="yes">yes <input type="radio" name="lab4e5q1" value="no">no <input type="radio" name="lab4e5q1" value="confused">I'm confused</font></p> <p><font color="#FF0000">Could you have come up with something similar on your own?<br> <input type="radio" name="lab4e5q2" value="yes">yes <input type="radio" name="lab4e5q2" value="no">no <input type="radio" name="lab4e5q2" value="maybe">maybe</font></p> <p><font color="#FF0000"></font> </p> <p><a href="lab4e5s4.htm" target="program">Click here for WATER step 4:</a></p> <p>You can work on any unfinished part to do the next refinement.<br> But let's work on the <strong>PROCESS STEP</strong>.<br> Since the processing for Home Users and Industrial Users is different, we decide to use a selection statement ("if") to break the processing into two parts).</p> <p><a href="lab4e5s5.htm" target="program">Click here for WATER step 5:</a></p> <p>We decide to continue refinement the <strong>PROCESS STEP</strong>, since processing and output are so closely related for this problem, we distribute the output into the processing part and refine it a little also.<br> Notice the use of the selection statement again to classify the different kinds of water usage.<br> Notice that each classification produces some output.</p> <p><a href="lab4e5s6.htm" target="program">Click here for WATER step 6:</a></p> <p>Let's go back to the <strong>INPUT STEP</strong> and continue refining there a while.<br> Let's put in some C++ code for the prompt using <em>cout</em>, the input using <em>cin</em>, and the validity check using an <em>if</em> statement.<br> Checking the validity for <em>gallon</em> is pretty easy, just make sure it is not a negative number.<br> If the input is not valid, we return 1 to indicate that there was a problem running this program</p> <p>Checking the validity for <em>cat</em> is more complicated since there are only 4 legal values ('H', 'h', 'I', and 'i'). So we combine them into one "if".<br> This may be the most confusing statement in the whole program because it combines four conditions into one statement.<br> You could approach this statement by refining it in smaller steps.. For instance.<br> // if (cat is not any of 'H', 'h', 'I' 'i') then invalid -- which means<br> // if(cat is not 'H' and it is not 'h' and it is not 'I' and it is not 'i') then invalid<br> in C++ the "is not" becomes "!=" and the "and" becomes "&&"</p> <p>NOTE: there are many other ways to check for validity, but this one is the shortest.</p> <p><font color="#FF0000">Do you understand this validity check (the first "if" statement)?<br> <input type="radio" name="lab4e5q3" value="yes">yes <input type="radio" name="lab4e5q3" value="no">no <input type="radio" name="lab4e5q3" value="maybe">kind of</font></p> <p><a href="lab4e5s7.htm" target="program">Click here for WATER step 7:</a></p> <p>Let's refine some more of the <strong>PROCESS STEP</strong> now. We convert the structured selection comments into C++ <em>if</em> statements using the appropriate C++ variables. <br> NOTICE: in checking the category of the user, we use the logical OR operator "||" of C++ and the logical equals "= =" </p> <p><a href="lab4e5s8.htm" target="program">Click here for WATER step 8:</a></p> <p>For the final refinement, we do the <strong>OUTPUT STEP</strong> to produce the final program.</p> <p> </p> <div align="center"><center><pre><img src="images/rainbow.gif" width="540" height="4"></pre> </center></div><div align="center"><center><pre><font size="4"><em><strong>Choose one when done</strong></em></font></pre> </center></div><div align="center"><center><pre><input type="submit" name="WORTHlab4e5" value="Too Detailed"> <input type="submit" name="WORTHlab4e5" value="Just Right"> </pre> </center></div><div align="center"><center><pre><input type="submit" name="WORTHlab4e5" value="More Detail Please"> <input type="submit" name="WORTHlab4e5" value="Waste of time"></pre> </center></div> </form> <hr> <h5>Copyright chris wild 1998.<br> For problems or questions regarding this web contact <a href="mailto:wild@cs.odu.edu">[Dr. Wild]</a>.<br> Last updated: February 10, 1998.<br> </h5>  </body>