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| Figure 1 |
What is an error?
Error is deviation from
actual and expected value.
It represents mistake made
by people.
What is a fault?
Fault is incorrect step,
process or data definition in a computer program which causes the program to
behave in an unintended or unanticipated manner.
It is the result of the
error.
What is a bug?
Bug is a fault in the
program which causes the program to behave in an unintended or unanticipated
manner.
It is an evidence of fault
in the program.
What is a failure?
Failure is the inability of
a system or a component to perform its required functions within specified
performance requirements.
Failure occurs when fault
executes.
What is a defect?
A defect is an error in
coding or logic that causes a program to malfunction or to produce
incorrect/unexpected results.
A defect is said to be
detected when a failure is observed.
So I wrote a C program as
mentioned below:
Add two numbers program
Example
1:
As mentioned this program
is required to add two numbers.
1 #include<stdio.h>
2
3 int
main ()
4 {
5 int
value1, value2, ans;
6
7 value1
= 5;
8 value2
= 3;
9
10 ans
= value1 - value2;
11
12 printf("The
addition of 5 + 3 = %d.", ans);
13
14 return
0;
15 }
When you compile and run
this program you see the printed statement as below:
The
addition of 5 + 3 = 2.
So after compiling and
running this program we realize the program has failed to do what it was
supposed to do.
The program was supposed to
add two numbers but it certainly did not add 5 and 3. 5 + 3 should be 8,
but the result is 2. There could be various reasons as to why the program
displays the answer 2 instead of 8. For now we have detected a failure.
As the failure has been
detected a defect can be raised.
Now lets go back to the
program and analyze what was the fault in the program.
1 #include<stdio.h>
2
3 int
main ()
4 {
5 int
value1, value2, ans;
6
7 value1
= 5;
8 value2
= 3;
9
10 ans
= value1 - value2; // ----> Bug
11
12 printf("The
addition of 5 + 3 = %d.", ans);
13
14 return
0;
15 }
We notice at line number
10, there is a ‘-’ sign present instead of ‘+’ sign. So the fault in the
program is the ‘-’ sign. Line 10 has the fault which caused the program to
deviate from the functionality.
Error is the mistake I made
by typing ‘-’ instead of ‘+’ sign. We have observed failure in correct
execution of the program. And in this case we can also say we have found the
bug.
A tester does not
necessarily have access to the code and may be just testing the functionality
of the program. In that case the tester will realize the output is
faulty and will raise a defect. Due to the observed wrong result it is known of
the fact that the program has an error which resulted in the fault in the
program and due to which the program failed to give the correct result. But the
tester may not know exactly what is causing the error.
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