Error: It is the term used to describe a non-conformance to
the explicitly stated requirement.
For example: Let me explain with an example. If the
requirement mentions 5 Plus 3 Divided by 4; the programmer
codes to add 5 and 3 first; and then divides the result [8]
by 4 to arrive at result 2.
But if the actual/intended application requirement is to
first divide 3 by 4 and then add 5; expecting a result 5.75
then this is a classic Design/Code Error.
Bug: Assume that the programmer has actually understood the
intended requirement correctly but has declared/stored the
result as an integer to show a result of 5 instead of 5.75 –
this is called a Bug. Here the programmer has to declare the
variable as “double or float” and not “int”.
Defect: A defect is any of the above but found/un-covered in
the “released-application” - running in the “Production
Servers” [gone “Live”] or may be in “Beta-Release”.

Please Explain Mathematically.Its Very Important.please

HI Priya, Please Explain Mathematically.Its Very
Important.please

error: means mistakes in the program
bug:means if the error is  rectified it is called bug
defect:if the error is not rectified it is called defect
small example for above scenario:
 take a pen it consists of cap,stiker....if stiker is lost 
that is called (ERROR),u can replace it with another stiker 
that is called (BUG),if pen has hole we can't replace 
it ,in that condition we called as (DEFECT)

the terms error,bug,defect are nearly inter connect to each 
other.
error:mistake in the program
defect:mistake found by the test engg is called defect
bug:if the defect is accepted by the developer is called 
BUG: in other words Expected result not equalto Actual 
result is called bug,
for other clarification mail me at 
phani555chintapalli@gmail.com
no:9247585911

If in the Req it is to first divide 3 by 4 and then add 5; 
Error : the programmer codes to add 5 and 3 first and then 
divides the result ( calculation is not doone as mentioned 
in the req )
Bug: programmer understands but declares the variable 
differently ie in this case, it must be double or float 
but declares it as int.

Defect:deviation from the requirement specification

Bug:deviation from the Functional specification

Error:related to source code like syntax error,logical 
error etc

In an interview point of vie all these sounds same which 
interrupts the succesful execution and expected out. But in 
general
Error: i sthe mistake performed by the developer like 
syntax error
Bug: is the deviation between the Actual out put and the 
expected output.
Defect: Bugs that are accepted by the developer is called 
defect

error : A mistake in a coding is called error

defect or issue:  due to errors in coding testing engineers 
are getting mismatches of our app. build this is defect or 
issue

bug: these defects or issues are accepted by the developers 
then it is bug.

Error: problem related to a program is called error.
Defect: problem that is identified by testing department is 
called defect.
Bug:error that is identified by development department is 
called bug.

In my opinion error and bug are same.