1. C++ Plus Data Structures
Nell Dale
Chapter 1
Software Engineering Principles
Modified from the Slides made by Sylvia Sorkin, Community College of Baltimore County - Essex Campus

2. Software Design Process

3. Programming Life Cycle Activities
Problem analysis understand the problem
Requirements definition specify what program will do
High- and low-level design how it meets requirements
Implementation of design code it
Testing and verification detect errors, show correct
Delivery turn over to customer
Operation use the program
Maintenance change the program

4. Software Engineering
A disciplined approach to the design, production, and maintenance of computer programs
that are developed on time and within cost estimates,
using tools that help to manage the size and complexity of the resulting software products.

5. Toolboxes: Hardware. Software
Ideaware (focus of the course!): the shared body of knowledge that programmers have collected over time, including algorithms, data structures, programming methodologies, tools…

6. An Algorithm Is . . .
A logical sequence of discrete steps that describes a complete solution to a given problem computable in a finite amount of time.

7. Goals of Quality Software
It works.
It can be read and understood.
It can be modified.
It is completed on time and within budget.

8. Specification: Understanding the Problem
Detailed Program Specification
Tells what the program must do, but not how it does it.
Is written documentation about the program.

9. Writing Detailed Specifications
Detailed Program Specification Includes:
Inputs
Outputs
Processing requirements
Assumptions

10. Program Design

11. Abstraction
A model of a complex system that includes only the details essential to the perspective of the viewer of the system.

12. Information Hiding
Hiding the details of a function or data structure with the goal of controlling access to the details of a module or structure.
PURPOSE: To prevent high-level designs from depending on low-level design details that may be changed.

13. Two Approaches to Building Manageable Modules
FUNCTIONAL DECOMPOSITION
OBJECT-ORIENTED DESIGN
Divides the problem
into more easily handled
subtasks, until the
functional modules
(subproblems) can
be coded.
Identifies various
objects composed of
data and operations,
that can be used
together to solve
the problem.
FOCUS ON: processes FOCUS ON: data objects

14. Functional Design Modules
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15. Object-Oriented Design
A technique for developing a program in which the solution is expressed in terms of objects -- self- contained entities composed of data and operations on that data.
cin
cout
>>
<<
get
Private data
setf
Private data . .
ignore

16. More about OOD
Languages supporting OOD include: C++, Java, Smalltalk, Eiffel, and Object-Pascal, C, …
A class is a programmer-defined data type and objects are variables of that type.
In C++, cin is an object of a data type (class) named istream, and cout is an object of a class ostream. Header files iostream.h and fstream.h contain definitions of stream classes.

17. Procedural vs. Object-Oriented Code
“Read the specification of the software you want to build. Underline the verbs if you are after procedural code, the nouns if you aim for an object-oriented program.”
Brady Gooch, “What is and Isn’t Object Oriented Design,”

18. Verification of Software Correctness
Testing
Debugging
Program verification

19. Program Verification
Program Verification is the process of determining the degree to which a software product fulfills its specifications.
SPECIFICATIONS
Inputs
Outputs
Processing
Requirements
Assumptions
PROGRAM

20. Program Testing
Testing is the process of executing a program with various data sets designed to discover errors.
DATA SET 1
DATA SET 2
DATA SET 3
DATA SET 4
. . .

21. Origin of Bugs Various Types of Errors:
Design errors occur when specifications are wrong
Compile errors occur when syntax is wrong
Run-time errors result from incorrect assumptions, incomplete understanding of the programming language, or unanticipated user errors.

22. Design for Correctness

23. Robustness
Robustness is the ability of a program to recover following an error; the ability of a program to continue to operate within its environment.

24. An Assertion studentCount is greater than 0
Is a logical proposition that is either true or false (not necessarily in C++ code).
EXAMPLES
studentCount is greater than 0
sum is assigned && count > 0
response has value ‘y’ or ‘n’
partNumber == 5467

25. Preconditions and Postconditions
The precondition is an assertion describing what a function requires to be true before beginning execution.
The postcondition describes what must be true at the moment the function finishes execution.
The caller is responsible for ensuring the precondition, and the function code must ensure the postcondition.
FOR EXAMPLE . . .

26. Design Review Activities
Deskchecking: tracing an execution of a design or program on paper (checklist Fig1.4, pg31).
Walk-through: a verification method in which a team performs a manual simulation of the program or design.
Inspection: a verification method in which one member of a team reads the program or design line by line an the others point out errors.

27. Program Testing Unit Testing: testing a module or function by itself
Data Coverage: testing all possible input values (Black Box Testing)
Code Coverage: testing program paths (Clear/White Box Testing)
Test Plans
Planning for Debugging
Integration Testing

28. Tasks within each test case:
determine inputs that demonstrate the goal.
determine the expected behavior for the input.
run the program and observe results.
compare expected behavior and actual behavior. If they differ, we begin debugging.

29. Integration Testing
Is performed to integrate program modules that have already been independently unit tested.
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30. Integration Testing Approaches
TOP-DOWN
BOTTOM-UP
Ensures correct overall
design logic.
Ensures individual modules
work together correctly,
beginning with the
lowest level.
USES: placeholder USES: a test driver to call
module “stubs” to test the functions being tested.
the order of calls.

31. Practical Considerations

32. Life-Cycle Verification Activities:
Analysis
Design
Code
Test
Delivery
Maintenance