sdds (1 Viewer)

[1234567]

ok...
reverse back engineering is decompile the code then do something from these code

decompilation is just translate it to source code

the question is
when you translate the program into source code, then learn the code (not develop anything from it, but study it), is this a situation for reverse back engineering or decomplation?

 

[iptteacherssuck]

reverse engineering is

going from source code to algorithm not machine code to source code. EG> Source to UML is reverse engineering

decompile is going from machine to source

 

[CHUDYMASTER]

Eh...no.

That's totally wrong.

Reverse engineering is the analysis of an existing system to obtain ideas to make a new one based on that. Decompilation is the conversion from machine code to assembler - human understandable code. Hence, it can be seen that decompilation is part of the reverse engineering process.

 

[iptteacherssuck]

no its not...

 

[sunny]

I think you might be both right

reverse engineering is going from source code to algorithm

Reverse engineering is the analysis of an existing system to obtain ideas to make a new one based on that

Strictly, reverse engineering does not necessarily require going from code to algorithms - you can analyse the workings of a program in many ways, not just using code converted to algorithms. So a more generic explanation would be chudy's one.

Decompilation is the conversion from machine code to assembler

decompile is going from machine to source

The textbook definition is to go from machine code to "usually assembler", but we all know that in reality its not always assembler. Many languages have decompilers that can take machine code and take it back to the original high-level source code.

But to answer the question, if you are using decompiled code to analyse the workings of the program, then you are using decompilation to reverse engineer the program.

Maybe Sam can get this one cleared up for us all.

 

[blah]

There was a multiple choice question in this year's catholic trials that totally relates to this discussion.

A software developer took a piece of code from a website through the process of reverse engineering. How can this be defined?

a) Compiling code that had yet to be translated
b) Taking a program from the site, fixing the problem then replacing it with a new version
c) Looking at the original design and do an analysis check on it
d) Translating code that is executable back into a higher level programming language

i put "d" and the answer was "d" but i really wasnt sure in the exam coz i learnt that decompiling was from object code to a low-level language.

our skool accepted both "c" and "d".

 

[SamD]

Go Sunny, I think your explanation is great.

Blah, In regard to the Catholic MC, I too think d is the answer. I think your teacher is extremely generous if they paid a mark for c. c gives no indication that reverse engineering has occurred as your looking at the original design. d describes decompilation which is one form of reverse engineering.

 

[blah]

our teachers have no clue...

btw samd do u have a copy of last year's catholic trials coz i got a question

 

[SamD]

I don't...
but now I do....
just downloaded it from the files area here!
So whats the question?

 

[blah]

cool thnx for being so helpful.if only u were my teacher

its 25c)i) about a truth table

i dun how they got the sample answer..

 

[del]

ooh.. i have a question too.

what's the story on using FOR - NEXT loops in pseudocode?

Can we use them or should we use WHILE - END WHILE?

i'm not exactly sure about that.... some say yes, some say no, so I'm just muddled

 

[blah]

the main thing i dun understand is how do u kno the value of C (if A is 1) and D (if B is 1) coz u dunno the other inputs to the AND gates. its obvious that the output would b 0 if either input is 0, but wot bout if u only kno one of them is 1? u kno wot i mean?



and oh yeh isit FOR-NEXT or FOR-ENDFOR ??? or both?

 

[SamD]

The question is terrible! And the suggested solution is even worse!

If I had to answer this question in an exam I'd have 8 rows, two for each A B combination, one with Q and Q dash initially set at 1 0 and the other with them set at 0 1. Even so there will still be inputs that cannot be resolved.

With about 24 hours till the exam I wouldn't waste time on such nonsense questions!

 

[blah]

lol ok i thought it was pretty gay too.

so u cant have only 1 input into logic gates right? except the NOT ones

 

[SamD]

The syllabus is very unclear on this pseudocode FOR loop stuff. When I was working on my prelim book I contacted all the syllabus writers and as a consequence I included both as acceptable.

By the way, I was a Senior Marker for the old 3U course and we never worried about nonsense such as this. The logic of the algorithm is what's being marked. So long as the intent of the keywords is clear it was never an issue.

 

[SamD]

Absolutely you need two inputs, if the gate has two inputs. Logic gates can have more than two inputs, although this is not likely to occur in SDD questions.

 

[blah]

so in that terrible question b4, u would not kno wot C would be if A was 1, and wot D would b if B was 1 right?

 

[SamD]

True

Normally AND gates are used to disable inputs. For example if the input, in this case, from Q is 0 then the input at A has no effect on C.

 

[blah]

thnx a heap sam cya

 

[del]

heya Sam, one last question (it think) to do with file processing

If using EOF to check if its end of file

is this right?

BEGIN
OPEN file
WHILE NOT EOF(file)
Read line
//do stuff
.
.
.


in that we read the line after checking its not EOF?

but if we're using a sentinel value then we read a line first as in
BEGIN
OPEN file
read line
WHILE line <> ####
//do stuff
.
.
.

thanks... hehe your getting lots of questions today as last minute studying sets in