3.6.1+Error+Causes

=**__Error causes__**=


 * To see how to detect and prevent errors presented here can be found on page 3.6.2 Error Detection **

Data Entry
 * Often times human error
 * Origin from
 * Entering data, which is not the original data, i.e. there was an error during the transaction of the data
 * While recording the original data errors might occur
 * Usually occurs accidentally
 * ex. Typing in the number 245 instead of 145, because the user hit the wrong key
 * ex. Using a comma instead of a point for decimal numbers or vice versa

Accidental
 * A user might accidentally produce an error. This could be hitting the wrong key (accidentally) or in form of the data entry errors described above.

Deliberate
 * Errors caused by a user intentionally
 * ex. Students breaking into the school system and changing their grades there

Software
 * Software can cause errors
 * ex. When software contains bugs, they might cause runtime errors or logical errors
 * ex. for logical error: A program to calculate the total expenses of buying certain products. However instead of adding the prices of the products to each other, it is multiplying them, generating a wrong result due to a logic error.
 * ex. for runtime error: A program might try to access an index of an array, which doesn't exist. So it might try to access the 11th element of an array, which only contains 10 elements. This would produce a runtime error.
 * ex. Software might conflict with other software, producing an error. For instance, two programs might try to access the same file at once, possibly resulting in one or both applications to crash.
 * ex. Wrong configurations might make software to act in a wrong or unexpected way . For instance, errors might occur when a wrong graphics driver tries to power the graphics card.

Hardware
 * Hardware failures can cause errors
 * ex. CDs: their surface might be scratched, resulting in errors, as the CD can't be read properly anymore
 * ex. Hard disks might crash, resulting in error
 * Interference - electrical interference might alter the data
 * Electrical interference could flip the bits, i.e. a 1 could become a 0 and vice versa. This could happen during storage but especially during transmission of data, ex. through a network
 * ex. A 13 in decimal is 1101 in binary notation.If the first bit was to be flipped, it would be 0101, which would be 5 in binary - very different to the beginning 13.

Vocabulary? Types of errors:

Desrcibe the following causes of errors with reference to an application in each case:
 * data entry error;
 * logic error;
 * syntax error;
 * runtime error;
 * transmission error;
 * data integrity

Last edit by: Jocbe Last update: 18. April 2011

Sources:
 * Jones, Richard. Computer Science Java Enabled. Victoria: IBID Press, 2004.