C Plus Data Structures

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

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Software Design Process
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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

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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.

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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

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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.

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Goals of Quality Software

• It works.
• It can be read and understood.
• It can be modified.
• It is completed on time and within budget.

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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.

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Writing Detailed Specifications

• Detailed Program Specification Includes
• Inputs
• Outputs
• Processing requirements
• Assumptions

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Program Design
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Abstraction

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

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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.

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Two Approaches to Building Manageable Modules
OBJECT-ORIENTED DESIGN

• FUNCTIONALDECOMPOSITION

FOCUS ON processes FOCUS ON data
objects
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Functional Design Modules
Main
Get Data
Prepare File for Reading
Print Data
Print Heading
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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
ltlt
gtgt
setf
get
Private data
Private data
. . .
. . .
ignore
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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.

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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 Isnt Object
  Oriented Design, 1989.

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Verification of Software Correctness

• Testing
• Debugging
• Program verification

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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
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Program Testing

• Testing is the process of executing a program
  with various data sets designed to discover
  errors.

DATA SET 4 . . .
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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.

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Design for Correctness
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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.

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An Assertion

• 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 gt 0
• response has value y or n
• partNumber 5467

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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 . . .
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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.

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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

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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.

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Integration Testing

• Is performed to integrate program modules that
  have already been independently unit tested.

Main
Get Data
Prepare File for Reading
Find Weighted Average
Print Weighted Average
Print Data
Print Heading
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Integration Testing Approaches
BOTTOM-UP

• TOP-DOWN

Ensures individual modules work together
correctly, beginning with the lowest level.
Ensures correct overall design logic.
USES placeholder USES a test driver
to call module stubs to test the
functions being tested. the order of calls.
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Practical Considerations
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Life-Cycle Verification Activities

• Analysis
• Design
• Code
• Test
• Delivery
• Maintenance