Table Of ContentErgonomics and industrial EnginEEring
Computer
Computer systems have become an important element of the world economy,
with billions of dollars spent each year on development, manufacture, oper-
ation, and maintenance. Combining coverage of computer system reliability,
safety, usability, and other related topics into a single volume, Computer System
System Reliability: Safety and Usability eliminates the need to consult
many different and diverse sources in the hunt for the information required to
design better computer systems.
Reliability
After presenting introductory aspects of computer system reliability such as
safety, usability-related facts and figures, terms and definitions, and sources
for obtaining useful information on computer system reliability, safety, and
usability, the book:
• Reviews mathematical concepts considered useful to understanding
Safety and Usability
subsequent chapters
• Presents various introductory aspects of reliability, safety, and usability
and computer system reliability basics
• Covers software reliability assessment and improvement methods
• Discusses important aspects of software quality and human error and
software bugs in computer systems
• Highlights software safety and Internet reliability
• Details important aspects of software usability including the need for
considering usability during the software development phase, software
usability engineering process, software usability inspection methods,
software usability test methods, and guidelines for conducting software
usability testing
• Elucidates web usability facts and figures, common design errors,
web page design, tools for evaluating web usability, and questions to
evaluate website message communication effectiveness
• Examines important aspects of computer system life cycle costing
Written by systems reliability expert B.S. Dhillon, the book is accessible
to all levels of readership, making it useful to beginners and seasoned
professionals alike. Reflecting practical trends in computer engineering
especially in the area of software, Dhillon emphasizes the importance of
usability in software systems and expands reliability to web usability and
management. It provides methods for designing systems with increased
reliability, safety, and usability.
K16634 B. S. D h i l l o n
ISBN: 978-1-4665-7312-3
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9 781466 573123
K16634_Cover_mech.indd All Pages 4/11/13 4:08 PM
Computer
System
Reliability
Safety and Usability
Computer
System
Reliability
Safety and Usability
B. S. D H I L L O N
Boca Raton London New York
CRC Press is an imprint of the
Taylor & Francis Group, an informa business
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Version Date: 20130410
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This book is affectionately dedicated to all my Scythian ancestors
for their firm belief in number 40. (This is my 40th book!)
Contents
Preface .....................................................................................................................xv
About the Author ...............................................................................................xvii
1. Introduction .....................................................................................................1
1.1 Background ............................................................................................1
1.2 Facts, Figures, and Examples ..............................................................1
1.3 Terms and Definitions ..........................................................................3
1.4 Sources To Obtain Information Related to Computer System
Reliability, Safety, and Usability .........................................................4
1.4.1 Journals and Magazines .........................................................5
1.4.2 Conference Proceedings .........................................................5
1.4.3 Standards and Handbooks .....................................................5
1.4.4 Data Sources .............................................................................6
1.4.5 Books..........................................................................................7
1.5 Scope of the Book ..................................................................................8
References .........................................................................................................9
2. Basic Mathematical Concepts ....................................................................13
2.1 Introduction .........................................................................................13
2.2 Arithmetic Mean and Mean Deviation ............................................13
2.2.1 Arithmetic Mean ....................................................................14
2.2.2 Mean Deviation ......................................................................14
2.3 Boolean Algebra Laws ........................................................................15
2.4 Probability Definition and Properties ..............................................16
2.5 Probability-Related Definitions .........................................................17
2.5.1 Cumulative Distribution Function ......................................17
2.5.2 Probability Density Function ...............................................18
2.5.3 Expected Value .......................................................................19
2.6 Probability Distributions ...................................................................19
2.6.1 Exponential Distribution ......................................................20
2.6.2 Rayleigh Distribution ............................................................21
2.6.3 Weibull Distribution ..............................................................21
2.6.4 Bathtub Hazard Rate Curve Distribution ..........................22
2.7 Laplace Transform Definition, Common Laplace
Transforms, and Final-Value Theorem’s Laplace Transform ........22
2.7.1 Laplace Transform: Final-Value Theorem ..........................23
2.8 Laplace Transforms’ Application in Solving First-Order
Differential Equations ........................................................................24
References .......................................................................................................26
vii
viii Contents
3. Reliability, Safety, and Usability Basics ..................................................29
3.1 Introduction .........................................................................................29
3.2 Bathtub Hazard Rate Curve ..............................................................29
3.3 General Reliability-Related Formulas ..............................................31
3.3.1 Failure (or Probability) Density Function...........................31
3.3.2 Hazard Rate (or Time-Dependent Failure Rate)
Function .................................................................................31
3.3.3 General Reliability Function ................................................32
3.3.4 Mean Time to Failure ............................................................33
3.4 Reliability Configurations .................................................................34
3.4.1 Series Network .......................................................................34
3.4.2 Parallel Network ....................................................................37
3.4.3 k-out-of-m Network ................................................................39
3.4.4 Standby Redundancy ............................................................41
3.4.5 Bridge Network ......................................................................42
3.5 Reliability Evaluation Methods ........................................................44
3.5.1 Failure Modes and Effect Analysis (FMEA) ......................44
3.5.2 Fault Tree Analysis (FTA) .....................................................45
3.5.2.1 Common Fault Tree Symbols ...............................45
3.5.2.2 Steps Involved in Developing a Fault Tree .........46
3.5.2.3 Probability Evaluation of Fault Trees ..................46
3.5.3 Markov Method .....................................................................48
3.6 Need for Safety and the Role of Engineers
in Designing for Safety ......................................................................51
3.7 Classifications of Product Hazards ..................................................52
3.8 Human Factors Basics for Engineering Usability ..........................53
3.8.1 Comparisons of Humans’ and Machines’
Capabilities/Limitations .......................................................54
3.8.2 Typical Human Behaviors and Their Corresponding
Design Considerations ..........................................................55
3.8.3 Human Sensory Capacities ..................................................55
3.8.3.1 Touch ........................................................................56
3.8.3.2 Sight ..........................................................................56
3.8.3.3 Vibration ..................................................................57
3.8.3.4 Noise ........................................................................58
References .......................................................................................................59
4. Computer System Reliability Basics.........................................................61
4.1 Introduction .........................................................................................61
4.2 Hardware Reliability Versus Software Reliability .........................61
4.3 Major Sources of Computer Failures and
Issues in Computer System Reliability ............................................62
4.4 Fault Classifications and Computer Reliability Measures ............64
4.5 Fault Masking ......................................................................................65
