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Computer Faults Explained

Computer faults can originate from specification mistakes, implementation mistakes, component defects, or external factors. A fault is a malfunction in the physical state or software code of a system that can lead to a logical error. An error is a logical state that may cause a failure. A failure occurs when a system does not meet its specified service. Faults are classified according to models including the physical-logical-effective machine model and the fault-error-failure model.

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Basit Khan
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67 views8 pages

Computer Faults Explained

Computer faults can originate from specification mistakes, implementation mistakes, component defects, or external factors. A fault is a malfunction in the physical state or software code of a system that can lead to a logical error. An error is a logical state that may cause a failure. A failure occurs when a system does not meet its specified service. Faults are classified according to models including the physical-logical-effective machine model and the fault-error-failure model.

Uploaded by

Basit Khan
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PPT, PDF, TXT or read online on Scribd
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1.

1 Fault Classification (ebook)

chp03 1
What are computer faults? Before answering,
we need to conceptualise faults in computer
systems.
• To better understand the fault tolerance
phenomena in a computer system, we need
fundamental concepts of computer faults, errors
and failures
– Analogous to the study of how electric current is generated in relation to the flow-

.
of-an-electron concept

• Here we need two models: physical-logical-


effective machines model and fault->error-
>failure model.
chp03 2
Fault-Error-Failure Three-
Machine Model
• Physical Machine
– system’s physical parts and software code
• Logical Machine
– system’s logical part at the circuitry/gate level,
where programs are executed and data manipulated
• Effective Machine
– system’s universe, in which the external effect of
an error is exhibited

chp03 3
Faults -> Errors -> Failures
• A fault: that part of the system’s physical state or
software code which malfunctions (per system
spec), leading to a logical error in the system (may
not be instant, ie a latent fault)
• An error: that part of the system’s logical state
which is liable to lead to a failure (may not be
instant, ie a latent error)
• A system failure: that state of delivered service not
complying with the specified service
chp03 4
Pondering:
• We know a computer failure is caused by a computer error
that is in turn caused by a computer fault. But what are the
possible causes of a computer fault? See next slide…

chp03 5
What are the causes/origin of
computer faults?
• specification mistakes
– incorrect algorithms, incorrectly specified requirements (timing, power,
environmental)
• implementation mistakes
– poor design, software coding mistakes
• component defects
– manufacturing imperfections, random device defects,
– components wear-outs
• external factors
– radiation, lightning, operator mistakes

chp03 6
chp03 7
How could we classify faults
according to their temporal
nature? … next lecture…

chp03 8

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