Software errors: Software bugs in a Soviet early-warning monitoring system nearly brought on nuclear war in 1983, according to news reports in early 1999. The software was supposed to filter out false missile detections caused by Soviet satellites picking up sunlight reflections off cloud-tops, but failed to do so. Disaster was averted when a Soviet commander, based on what he said was a '...funny feeling in my gut', decided the apparent missile attack was a false alarm. The filtering software code was rewritten Designing and testing is critical. See Software QA and Testing faq at [http://www.softwareqatest.com/qatfa q1.html]. Do you like horror stories? http://www.cs.tau.ac.il/~nachumd/horr or.html Therac-25 Incident: Error in radiation doses to cancer patients. [http://courses.cs.vt.edu/cs3604/lib/Th erac_25/Therac_1.html] Also p. 202. Chapter 22 Design Software Life Cycle Analysis (Requirements) Design Implementation Testing Deployment Waterfall Model (p. 827) Appears logical but does not work very well in practice when problems are extremely complex. Not realistic to assume complex processes flow linearly. Imagine designing and building a home this way – with no option for change. True problem solving often occurs after flaws are discovered! Examples: • Often difficult to state all requirements exactly prior to the design phase. • Perhaps there were inconsistent requirements (not unusual when requirements are generated by many people). • Seeing results can change requirement expectations. Imagine the following requirements (among hundreds) for a game. Requirement 14. Only basic food staples shall be carried by game characters ...... Requirement 223. Every game character shall carry water. ...... Requirement 497. Flour, butter, milk and salt shall be considered the only basic food staples. Reference for the preceding slide, and other examples, at [http://www.ie.inf.uc3m.es/grupo/doce ncia/reglada/psii/SwEng2/Unit4.pdf]  Requirements are often changing (new rules or regulations).  A design may be sound in theory, but not in practice due to finite limits on computers (Reason for algorithm analysis).  Bug fixes sometimes require a redesign.  Customers might not like the final product (even though it was designed to their specs). They may have changed their mind or had a change in thinking.  Spiral model (p. 828).  Iterative approach to software development.  Can be more responsive to changes or inexperienced customers.  Can lead to inefficiencies (or sloppiness) because developers know there is another iteration in the process and may not be as complete in the current iteration. Much of this falls into the category of Systems Analysis or Project Management and is covered in depth in CS460. Ultimately, software should be “idiot proof”. OO Design Discover classes Determine class’ responsibilities Describe relationships among classes. Some things to bear in mind: Cohesion Interface features should be closely related to a single concept the class represents. See example on p. 834 If you account for half-dollars or silver dollars, you must change the CashRegister class. This is what you want to avoid. Coupling: Measure of the extent to which classes depend on other classes. Note: dependency relationship on p. 835. Maximize cohesion and remove unnecessary coupling. Class relationships: Inheritance. You’ve seen it and we’ll cover later. Dependency: Class A depends on class B if any of A’s methods use an object of type B in any way. Page 834-5: The CashRegister class depends on the Coin class. Aggregation  If an object of one class contains objects of another class then the first class aggregates the other.  stronger form of dependency.  If a class “is made up of” elements from another class, it may be an aggregation. Based on the information provided we don’t know if the CashRegister class aggregates the Coin class or just depends on it. Does the CashRegister class contain a list of coins or just the total value of the coins. It could be designed either way, though the first is probably best.  Strictly an interpretation of the realities of the model you’re dealing with.  A department is “made up of” employees, so a department may aggregate employees.  That is, the department class probably contains employee objects.  The book makes a reference to pointers. Forget about that for now. See side bar on page 837 Go through example of using inheritance vs aggregation. Multiplicity of an aggregation. See page 839. CRC Cards (Classes, Responsibilities, Collaborators). 1. Discover classes 2. Determine Responsibilities of each class 3. Describe relationships between classes Do the case study starting on page 839. Example: Model the NCAA basketball tournament. Display the scores of all games in a given round. Display the scores of all the games in a region. Display the scores of all games played by a given team. Display points scored by each player in each game played. Comparisons between C++ and Java Both are case sensitive. Both have similar syntax. Often causing some to think the languages are similar. THEY ARE NOT! Java is pure object oriented, C++ is not. C++ can have functions that are not members of a class. This can be an advantage but may also allow sloppy design. Java compilers typically generate byte code, standard C++ compilers generate machine code (.exe) file. Can run simply by double clicking on the .exe file or by specifying the file name in the run command. Byte code usually results in better portability; .exe files generally run faster. Major differences in parameter passing. Java: primitives are pass by value, objects are pass by reference C++: can specify how to pass parameters. C++ supports pointer variables and addresses, Java does not. C++ supports preprocessing and macros (code expansion). C++ allows you to define your own types. Java has automatic garbage collection, standard C++ does not. Java hides more specific machine details from the programmer. Can be good or bad, depending on the application. Also see Appendix I and [http://www.dickbaldwin.com/java/Jav a008.htm]. Can also search google using key words differences Java C++. Visual Studio .NET Specifics: Distinction between Managed (C++/CLI) and Unmanaged (standard C++) applications. This is not important for the course goals (primarily standard C++), but it can NOT be avoided entirely. In addition, it's important to note that the old Visual studio 2003 and 2005 versions of managed code are quite different. Some differences: C++/CLI (Common Language Infrastructure) Microsoft's extension to C++ for the .NET environment. [http://msdn.microsoft.com/enus/magazine/cc163681.aspx] Compiles to an Intermediate Language and runs in a virtual machine environment. Has access to both managed and unmanaged data. To oversimplify, managed provides some garbage collection abilities as in Java. [http://www.developer.com/net/cplus/print.php/219 7621] http://social.msdn.microsoft.com/Forums/en/xnaga mestudioexpress/thread/effcca73-b4f2-4a74-91e3cb92d2008a29 Standard C++ Well established language. Code may still be portable; it would just have to be recompiled. Compiles to machine code. Programmers have to do their own garbage collection. We’ll deal just with standard C++ and design. Managed code adds little to the goals of this course. We’ll distinguish ONLY when we have to. Creating your first unmanaged C++ program in Microsoft Visual Studio .NET 2008 Start Microsoft Visual Studio .NET. You can close the Start page if it appears. Make sure the Solution Explorer pane is visible by selecting ViewSolution Explorer. Select FileNewProject. Select the name of the project and the location in which it will be store. A folder will be created with this name at that location. Under Project Types select Visual C++WIN32. Also select WIN32 Console Application under Visual Studio installed templates. Specify a name and location for your project. Clear the checkbox associated with Create directory for solution next to the Solution name textbox. Checking it creates a subdirectory inside the one you are already creating. It’s not necessary for this course. Click OK. The WIN32 Application Wizard will appear. When it does, click on the Application Settings link. Select the Console Application radio button. Select the Empty Project textbox. Click the Finish button. You now have a project with no associated code and the Solution Explorer pane should contain three items (Header files, Resource files, and Source files) under the name of your project. In this course you will need to be concerned only with the header and source files. In the Solution Explorer pane, right click on Source files and select AddNew Item. In the Categories pane, select Visual C++Code. Select C++ file under Visual Studio Installed Templates. Enter a name for the file in the textbox provided (You do not need to specify .cpp in the name). Leave the location as it is (your solution directory). Click the Add button. A window will appear in which you can enter some C++ code. Enter the C++ Code in the window associated with the file you just created. For example, enter the code below #include <iostream> using namespace std; int main() { cout << "Hello: This is your first C++ Program" << endl; cin.get(); return 0; } Press the F5 key to run the program. A console window will appear with the message above. Press the Enter key to exit the program. At this point you can exit Visual Studio .NET, saving your files. To restart Visual Studio .NET and run the same program, double click on the solution file (File with the ”sln” extension) in the solution folder. To run this program without entering the Visual Studio .NET environment, double click on the “exe” file found in the Debug folder. Creating a C++ Program in Microsoft Visual Studio .NET with a simple user interface (optional). Proceed as describe previously except Under Project Types select Visual C++CLR Also select Windows Form Application under Visual Studio installed templates. You may have to specify “C" drive location to avoid a trusted user warning. A blank form will appear allowing you to drag gui elements onto it. Make the toolbox visible by selecting ViewtoolBox. Use the toolbox to drag and drop various gui elements onto the form Example: Create one button and textbox: Put textBox1->Text = "0" in the form_load method. (You can get to this method by double clicking on the blank form) Put the following in the button_click method. (You can get to this method by double clicking on the button) int t = Int32::Parse(textBox1->Text); t++; textBox1->Clear(); textBox1->AppendText(t.ToString()); We will NOT do much with GUI interfaces. Software often follows a 3-tier design as below. This course focuses on the middle tier. Interface (GUI or console) Program logic Data (files or database)