ECE 264Object-Oriented

Software Development

Instructor: Dr. Honggang WangSpring 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\<username>

For MSDN account, e-mail Andrew Smart (andrew.smart@umassd.edu) MUST contact Andrew using your UMassD e-mail After 2 weeks

Software design cycle General overview

Software engineering steps Types of testing

Requirements specifications Introduce UML, use case diagrams

C++ basics

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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 statementsint 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. 1 b. 2 c. 4 d. 5

 2. Now, if x = 5, y is equal to: a. -2 b. 3 c. 5 d. 6

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Pretest review: loopsint 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. 2 b. 3 c. 4 d. an infinite number of

4. The final value of x is: a. 2 b. 3 c. 8 d. 16  5. 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--)

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Pretest review: arrays, I/Oint 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\nb. A[i] + 3 = A[i] + 3c. A[0] + 3 = 3 d. A[1] + 3 = 10

  7. The value of A[4] is: a. 4 b. 5 c. 12 d. non-existent

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Notes: http://www.cplusplus.com/reference/clibrary/cstdio/printf/

Pretest review: switch statementsswitch (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. 1 b. 4 c. 5 d. 6  9. var = 2? a. 2 b. 3 c. 6 d. 7  10. var = 5? a. 0 b. 5 c. 10 d. 25

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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

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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

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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

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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

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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.

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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?

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Use case modeling

Source: http://newportoregon.gov/dept/npd/atmsafety.asp

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15

Fig. 2.18 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

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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

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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

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Basic Program 1// Adapted from figure 2.1 in text// Text-printing program#include <iostream> // Allows program to

// output data to the screenusing std::cout;

// function main begins program executionint main() {

// display messagecout << "Welcome to C++!\n";

return 0; // indicate program ended successfully

} // end function main

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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

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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

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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

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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

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Modified program: two cout statements// Adapted from figure 2.3 in text// Printing a line of text with multiple statements#include <iostream> // Allows program to

// output data to the screenusing std::cout;

// function main begins program executionint main() {

// display messagecout << "Welcome " cout << "to C++!\n";

return 0; // indicate program ended successfully

} // end function main

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Modified program: multiple output lines

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// Adapted from figure 2.4 in text// Printing multiple lines of text with one statement#include <iostream> // Allows program to

// output data to the screenusing std::cout;

// function main begins program executionint main() {

// display messagecout << "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;

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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

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Basic program 2// Adapted from figure 2.5 in text// Addition program that displays the sum of two integers.#include <iostream>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

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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, 8th ed. Etter & Ingber, Engineering Problem Solving with

C++, 2nd ed.

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