Cable Forum - What is a RAR file?

Cable Forum (https://www.cableforum.uk/board/index.php)

- General IT Discussion (https://www.cableforum.uk/board/forumdisplay.php?f=19)

- - What is a RAR file? (https://www.cableforum.uk/board/showthread.php?t=27565)

What is a RAR file?

I know I have asked before, but I can't find it again.

what is a RAR file and I have a few files that i got sent from someone, it has a lot of files
like:
this.r00
this.r01
this.r02
this.rar
this.sfv

I am not sure what to do with these, or how to open them up, does the r00 r01 etc have anything to do with the rar file? and what is sfv?

also where can i find out about file extensions?

ik

Re: What is a RAR file?

http://www.rarlab.com/rar_file.htm answers part of your questions.

Re: What is a RAR file?

Rar files is an alternative form of compression to zip.

Check this link: http://www.rarlab.com/rar_file.htm

edit: someone is a tad quicker at googleing than me ;)

Re: What is a RAR file?

Hi, sorry for the terse answer, but am a bit rushed here, hope this helps

RAR is a type of compression similar to ZIP, you will need a program like WinRAR to open them http://www.rarlab.com/

I am guessing here that the ".r01" ".r02" etc are similar to winzip's multi-floppy spanning feature.

SFV stands for Simple File Verification, its is basically a mathematical short checksum number based on the original file. ie a poor mans MD5 hash.

http://www.wotsit.org/ is a reasonable place to start looking up what file extensions mean

EDIT
dealing with my other chat windows meant most of this is was not necessary,oh well,c'est la vie.

Re: What is a RAR file?

sfv files (Simple File Verificator) are used to check if all parts of a rar download are present and correct. http://dreamlover.tecbox.com/faqsfv.htm

Re: What is a RAR file?

Open up the .rar.

This in turn will open up the all the split files and display all the files between them ready to extract.

Re: What is a RAR file?

if the rar files are being accessed via newsgroups, it is much easier if you use a client that understands them - outlook & express fail to understand rar & Yenc, atm ...

Re: What is a RAR file?

Aah .rar - the warez community's best friend. ;)

Re: What is a RAR file?

Surely .par or .par2 :LOL:

Theres a rep for anyone who can explain how they work in words i understand :)(not how you use them but how they make something out of nothing they must be female)

Re: What is a RAR file?

Firstly, you take a very big file -- say a disk image of a CD, about 700MB. Then you compress it, using a type of compression called RAR. This is similar to Zip, but can create smaller files.

When you've done this, you might have got it down to 400MB or so. The trouble is, that's still far too big for lots of people to download. Fortunately, the RAR format has a rather clever method of splitting one blig compressed file into lots of little ones. In this way, the data files are labled file.r01, file.r02, etc. There is also a "control" file called file.rar, which knows how many subfiles there are, and how to put them back together. When you open this control file in WinRAR, it automatically loads all the r01, r02 etc files (or gives you an error if they aren't all there).

As to how they work internally, well that starts simple but quickly gets very complicated and mathematical. What happens is that the compressor looks for patterns in the file. So, for example, if the sequence 1234567890 occurs several times in a file, then the compressor will say, let a=1234567890, and replace that list of numbers with the reference a. In this way, the new file is smaller than the previous one. The compressor also puts an instruction at the beginning of the file for the decompressor to do the opposite, so that you get the original file back just as it was.

Okay, so it's about a billion times more complicated than that -- maths PhDs have been done on file compression -- but that's how it starts....

EDIT: Read all about it here: http://computer.howstuffworks.com/file-compression.htm

Re: What is a RAR file?

Quote:

Originally Posted by zinglebarb

Surely .par or .par2 :LOL:

Theres a rep for anyone who can explain how they work in words i understand :)(not how you use them but how they make something out of nothing they must be female)

Quote:

Originally Posted by Tristan

This is a very good discription of a rar , I will rep you for that once Ive spread enough love as it were ,
Its par files i do not understand ,I can use them , But i just don't understand them :D

Re: What is a RAR file?

Quote:

Originally Posted by zinglebarb

This is a very good discription of a rar , I will rep you for that once Ive spread enough love as it were ,
Its par files i do not understand ,I can use them , But i just don't understand them :D

In this instance PAR is short for parity, and ".Par" files can be thought of as being analogous to a RAID unit, but for a RAR archive. See these links for further reading.

http://www.techsono.com/faq/rar.html

http://www.slyck.com/ng.php?page=6

Re: What is a RAR file?

Many programs can unpack RAR - even some of the free ones, but nothing else can create this closed, proprietary format.

The OPEN alternative to RAR, is 7-zip's "7Z" format, becoming a standard among the free ones, though only the current 7-zip betas can do multipart in it.

Just say no to proprietary formats!

PAR has two forms, the older and easir to understand one - the basic concept is similar to that used in an old tape backup - the "XOR Group".

In that, an additional block of data that is the bitwise exclusive-or of all the grouped blocks is recorded. If one block is missing, all the remaining ones can be xor'ed back out of the XOr group, leaving the missing one.

That's still an oversimplification, as extending it to cover more than one lost block in a group is difficult.

The use of PAR2, which allows partial blocks to be used, is even harder to explain, especially as it can also use data blocks that have been "cut & shut" where segments are missing.