ECE 264 Object-Oriented Software Development Instructor: Dr. Honggang Wang Spring 2013 Lecture 2: Software Design Cycle, Requirements Specification and C++ Basics

Lecture outline Announcements/reminders  Class folder now set up on M:\ drive Should have folder under M:\ECE-264\  For MSDN account, Andrew Smart MUST contact Andrew using your UMassD After 2 weeks Software design cycle  General overview Software engineering steps Types of testing Requirements specifications  Introduce UML, use case diagrams C++ basics 9/28/2016 ECE 264: Lecture 2 2

9/28/2016 ECE 264: Lecture 2 3 Pretest review Pretest intended to review the following  Control structures (if/else, switch, loops)  Basic data types  Array accesses  C output First three topics use exactly the same syntax in C++! We’ll cover C++ output starting in lecture 3

Pretest review: if/else statements int x, y;. if (x < 5) { y = x + 1; } else { y = x – 2; } 1. At the end of the if/else statement above, if x = 4, y is equal to: a. 1b. 2 c. 4d Now, if x = 5, y is equal to: a. -2b. 3 c. 5d. 6 9/28/2016 ECE 264: Lecture 2 4

Pretest review: loops int x = 1; int i = 0; while (i <= 3) { x = x * 2; i++; } 3. Fill in the blank: The body of the while loop executes ______ times. a. 2b. 3 c. 4 d. an infinite number of 4. The final value of x is: a. 2b. 3 c. 8 d Which of the following is a for loop that can replace the while loop and produce the same result for x? a. for (i = 1; i < 4; i++) b. for (i = 0; i < 3; i++) c. for (x = 0; x <= 3; x++) d. for (i = 3; i >= 0; i--) 9/28/2016 ECE 264: Lecture 2 5

Pretest review: arrays, I/O int A[5] = {0, 7, 13, 12, 5}; for (i = 0; i < 5; i++) { printf(“A[%d] + 3 = %d\n”, i, A[i] + 3); } 6. In the first iteration, the program will display the following text on the screen: a. A[%d] + 3 = %d\n b. A[i] + 3 = A[i] + 3 c. A[0] + 3 = 3 d. A[1] + 3 = The value of A[4] is: a. 4 b. 5 c. 12 d. non-existent 9/28/2016 ECE 264: Lecture 2 6 Notes:

Pretest review: switch statements switch (var) { case 0: case 1: x = x + var; break; case 2: x = x – var; case 3: x = x * var; break; default: x = var; } Assume x always equals 5 at the start of the switch statement. What is the value of x at the end of the statement if: 8. var = 1? a. 1b. 4 c. 5 d var = 2? a. 2b. 3 c. 6 d var = 5? a. 0 b. 5 c. 10 d. 25 9/28/2016 ECE 264: Lecture 2 7

Software design cycle Software engineering: application of systematic approach to development, operation, and maintenance of software  Not just programming!  Lots of management involved Traditional software design cycle  Requirements engineering  Design  Programming  Integration  Delivery  Maintenance 9/28/2016 ECE 264: Lecture 2 8

Software engineering cycle phases Requirements: Client needs  Translate these into requirements specification Design:  Developers translate requirements to actual product  Iterative process Start with broad outline: what’s the overall functionality we need? Break that down into smaller pieces: what modules are needed? What details are needed for each module? How do modules interact? Final result of this stage: design specification Can include  Verbal description of design, both at high & low level  UML diagrams showing varying levels of detail about project 9/28/20169 ECE 264: Lecture 2

Software engineering cycle phases (cont.) Programming: Write the actual code  Translate the design spec into language of choice  May have multiple programmers handling different modules Integration: Merge modules together  The different pieces of software are merged together. Testing is crucial in this phase to ensure the software works and meets all the requirements of the clients. Delivery: Get product to client  Client typically conducts acceptance testing to ensure product meets requirements Maintenance:  Fix remaining bugs  Modify product to meet new requirements 9/28/ ECE 264: Lecture 2

Testing Testing is key from design stage on  Unit testing: does a given module function in the expected manner? You use unit testing every time you debug an individual method, class, etc.  Integration testing: do modules fit together? Multiple functions calling one another; compatibility among classes; merging files from different parts of the program  System testing: does whole system work together?  Acceptance testing: user-designed tests with developer support to ensure product meets requirements Good idea to formulate testing plans in design stage  As you determine design spec, think about how you’re going to test your software 9/28/2016 ECE 264: Lecture 2 11

Use case modeling Often preceded by “requirements gathering”  Formal name for “figure out what the clients want”  Can be done through use case modeling Formally model interactions of user(s) with system  Can then go from use cases to requirements specification Take general use cases and break down into more specific examples Formalize these steps into a specification for actions May also have to specify data to be stored, states to be kept, etc. 9/28/2016 ECE 264: Lecture 3 12

Use case diagrams Textbook example: ATM system  Assume we’re designing software for basic ATM  Given hardware description of user interface Screen to display messages Keypad for numeric input  Assume account # must be entered Cash dispenser Deposit slot  For what operations might someone want to use this ATM? 9/28/2016 ECE 264: Lecture 3 13

Use case modeling Source: 9/28/2016 ECE 264: Lecture 3 14

15 Fig Use case diagram for the ATM system from the user’s perspective.

From use case to requirements spec. What steps occur before accessing account?  Screen displays basic welcome message  Enter account #  Screen prompts user to enter PIN  Screen displays main menu if PIN correct; error otherwise (and returns to welcome) What steps should we take to withdraw money?  Choose “Withdraw money” option from menu  Screen displays amounts to be withdrawn, option to cancel, potentially option to enter different amount  Based on user input, system either proceeds with withdrawal or cancel To proceed, must check two conditions: account has enough money, and ATM has enough cash available Display error message if either condition is not true Supply money and debit account otherwise 169/28/2016 ECE 264: Lecture 3

UML diagrams Use case diagram is example of Unified Modeling Language (UML) diagram  General-purpose modeling language  Uses graphical techniques to create abstract system models Can use UML to describe  Requirements: how can someone use system?  Design: both at high and low level Overall and specific structures Overall and specific behaviors 9/28/2016 ECE 264: Lecture 3 17

UML diagrams Thirteen types of UML diagram  Model either system structure or system behavior  We’ll focus on: Use case diagram: model interactions between system and external entities in terms of system capabilities Class diagram: shows classes: building blocks of system State machine diagram: models way in which object changes state (i.e., attributes change value) Activity diagram: models actions performed and specifies order for an object Communication diagram: shows interaction between objects; focus on what interactions occur Sequence diagram: shows interaction between objects; focus on when interactions occur 9/28/2016 ECE 264: Lecture 3 18

Basic Program 1 // Adapted from figure 2.1 in text // Text-printing program #include // Allows program to // output data to the screen using std::cout; // function main begins program execution int main() { // display message cout << "Welcome to C++!\n"; return 0; // indicate program ended successfully } // end function main 9/28/2016 ECE 264: Lecture 3 19

Namespaces; using Directive The using directive instructs the compiler to use files defined within a specific namespace  Namespaces allow us to declare different scopes  Typically written right after the relevant header file(s) Example: using namespace std;  std is the name of the Standard C++ namespace  Including this line allows you to avoid specifying namespace for every identifier in your headers …  … but allows everything in the std namespace  Compromise: list namespace members actually used using std::cout; Otherwise, you’d have to write “ std::cout ” every time 9/28/2016 ECE 264: Lecture 3 20

Input/output streams C++ has three standard input/output streams  cin is the standard input (e.g., keyboard)  cout is the standard output  cerr is the standard error 9/28/2016 ECE 264: Lecture 3 21

Input/output streams (cont.) Standard output  Use the stream output operator << to direct data to cout  General Form: cout << expression << expression;  Note: An expression is a C++ constant, identifier, formula, or function call.  endl can be used to place an output character in the buffer and flush the buffer 9/28/2016 ECE 264: Lecture 3 22

23 Modifying Our First C++ Program Two examples  Print text on one line using multiple statements (Fig. 2.3) Each stream insertion resumes printing where the previous one stopped  Print text on several lines using a single statement (Fig. 2.4) Each newline escape sequence positions the cursor to the beginning of the next line Two newline characters back-to-back outputs a blank line 9/28/2016 ECE 264: Lecture 3

Modified program: two cout statements // Adapted from figure 2.3 in text // Printing a line of text with multiple statements #include // Allows program to // output data to the screen using std::cout; // function main begins program execution int main() { // display message cout << "Welcome " cout << "to C++!\n"; return 0; // indicate program ended successfully } // end function main 9/28/2016 ECE 264: Lecture 3 24

Modified program: multiple output lines 9/28/2016 ECE 264: Lecture 3 25 // Adapted from figure 2.4 in text // Printing multiple lines of text with one statement #include // Allows program to // output data to the screen using std::cout; // function main begins program execution int main() { // display message cout << "Welcome\nto\n\nC++!\n"; return 0; // indicate program ended successfully } // end function main

Another C++ Program: Adding Integers Variable  Is a location in memory where a value can be stored  Common data types (fundamental, primitive or built-in) int – for integer numbers char – for characters double – for floating point numbers  Declare variables with data type and name before use int integer1; int integer2; int sum; 9/28/2016 ECE 264: Lecture 3 26

Input streams Standard input  Use the stream input operator >> to direct keyboard input to variables  General Form: cin >> identifier >> identifier;  Input value must be compatible with identifier type 9/28/2016 ECE 264: Lecture 3 27

Basic program 2 // Adapted from figure 2.5 in text // Addition program that displays the sum of two integers. #include using std::cout; using std::cin; using std::endl; int main() { // variable declarations int number1; int number2; int sum; // prompt user for data and read into appropriate variables cout << "Enter first integer: "; cin >> number1; cout << "Enter second integer: "; cin >> number2; sum = number1 + number2; // add the numbers; store result in sum cout << "Sum is " << sum << endl; // display sum; end line return 0; // indicate that program ended successfully } // end function main 9/28/2016 ECE 264: Lecture 3 28

Final notes Next time Continue with C++ basics More examples of basic I/O Acknowledgements: this lecture borrows heavily from lecture slides provided with the following texts: Deitel & Deitel, C++ How to Program, 8 th ed. Etter & Ingber, Engineering Problem Solving with C++, 2 nd ed. 9/28/2016 ECE 264: Lecture 3 29