Ryan Thomson
Computer Science 35IB
Sir Winston Churchill High School
There are six basic types of computer errors: data entry,
accidental, deliberate, software, hardware and transmission.
An error must not fall under only one of these types, a
single error can also be of one or more types.
Data entry errors occur when a user inputs a value to the
computer that is either invalid or of bad type. Suppose
that a user inputted a real floating point number when an
integer was expected, this would cause a data entry error.
Also data entered can be of the correct type but be out of
bounds or otherwise invalid and still cause a data entry
error.
An accidental error occurs when it was not the intent of the
the user to initiate the error. This means that if the user where
to somehow crash the computer accidentally then that would
be classified as an accidental error. Accidental errors also
include hardware failure because it was not the intent of the
hardware manufacturer for their product to fail( hopefully ).
Deliberate errors occur when the user intentionally causes a
computer error. This can be done in any number of ways including,
known bad input, viruses, trojan horses and other malicious
software.
A software error occurs when any piece of software causes any
type of computer error that is possible by software. This
includes all errors that do not have anything to do with
hardware errors. Examples of this are a program crash.
Hardware errors occur when an actual hardware component of
a computer fails and thus creates the error. All hardware
can be classified as all errors that is not software based.
This can be a malfunctioning drive, bad RAM, a burnt-out
CPU, etc.
A transmission error occurs when there is a problem sending
or receiving data between two separate parts of a computer or
two separate computers. These errors can be software or
hardware based.
Errors can be detected by using validation. Errors in user
input can be detected by validating the inputted value through
the use of validation algorithms. After validation has found
the presence of an error, appropriate action can be taken to
eliminate or prevent the error. Data validation is can be in
the form of a full algorithm or a quick code snippet depending
on the data type and valid/invalid data range.
Another method of detecting errors is to use parity checks.
Parity checks can be used when ever data is transmitted from
one computer to another or from separate parts of the computer.
A "parity bit" is sent along with the data. This "parity bit"
is used to determine whether or not the data was sent or moved
correctly.
Here is how it works: before sending or moving the data, the
still valid data is checked to see whether it is even or odd
(in binary). If it is even, the parity bit is set to "1", if
the data is odd, the bit is set to "0". This bit is sent along
with the data and when it arrives, it is checked against the
data to determine if the data has changed or not.
Errors can be prevented through the use of two methods: validation
and verification. Validation was already covered in the previous
section on detecting errors. When talking in terms of preventing
errors, validation is a little different.
Validation is used mainly by programmers in their code to
properly check data for validity. Many algorithms exist to do this
and most of them are very specific to the data type and its valid
range. These algorithms check through the data and then determine
whether or not the data is valid.
Verification if similar to validation but it does not always have
to be in the form of algorithms or code. Any user can verify his
or her data and system to prevent errors. This verification can
be in the form of checking that you typed in data correctly to a
form or even running a disk scanner on your drives to check for
errors.
Methods of recovery from errors vary quite widely depending on
the type of error and/or the severity of the error.
Errors caused by bad user input can easily be handled through
the use of re-input. Re-input is very simple, the program just
asks the user for new, valid data and throws the old data away
in a safe manner.
Transmission errors are as easy to recover from as data entry
errors except they are harder to detect in some cases. If a
transmission errors occurs, the data can simply be re-transmitted.
this method is the only true way to recover from transmission
errors.
When a hard drive crash or another error of similar result
occurs, the only way to fully restore your old data is to
maintain a back-up copy of all the your software on some type
of external media. This can be either floppies for small back-up
needs, CDR's for larger amounts, and tape drives for even
larger amounts of data. Many back-up programs exist to that work
with all types of media. These programs automatically compress
( optionally ) your data and store it on the selected media for
later use. These programs can also be used in reverse to
uncompress ( if compressed ) data and restore is back to the
hard disk.
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