data validation / verification / security / errors / testing

Question 1

data validation definition

Answer 1

checks if data conforms to a set of specific requirements (to avoid errors)

Question 2

data validation methods

Answer 2

length check
range check
format check
presence check
check digit

Question 3

types of error that check digits usually detect

Answer 3

letter/digit errors (eg. I <—> 1)
single-digit errors (eg. 1 <—> 2)
transposition errors (eg. 21 <—> 12)

Question 4

data verification definition

Answer 4

ensures data entered is what user intended

Question 5

data verification methods

Answer 5

double entry
proof-reading data
checksum

Question 6

how should data backups be carried out

Answer 6

• carried out regularly (so that backups not too outdated)
• shld be stored offsite by copying info to physical storage like hard disk (so tht disasters causing loss of org data unlikely to affect backup)
• shld be tested regularly to ensure that backups can be restored wo error

Question 7

why backup?

Answer 7

• in case of catastrophic data loss, can restore data from most recent data backup
• minimises disruption to business operations

Question 8

why archive?

Answer 8

• to free up storage resources for frequently used data
• done by archiving data to cheaper storage

Question 9

name the 3 errors

Answer 9

• syntax error
• runtime error
• logic error

Question 10

give 3 examples of runtime error

Answer 10

• infinite loop, keep repeating code till it crashes / memory runs out
• infinite recursion, keep calling itself with (changes to parameter) till it crashes / memory runs out
• input too large in recursion, max recursion limit exceeded / stack overflow (call stack runs out of memory)

Question 11

why didnt data testing identify error that occurred during runtime?

Answer 11

• duration of the test is not long enough
• way of testing is incorrect / insufficient

application: if crash due to too much memory used –> data testing neglected some parts of the program bc usually only test if output right/wrong but X test how much memory it uses

Question 12

why infinite while loop occurs?

Answer 12

• program X reach terminating condition whr (state condition)
• (why X reach terminating condition) bc val (in condition) is not decremented/incremented