|
QUESTION: What is compression and why do I need it?
ANSWER:
As the name implies, anything that's compressed is SMALLER than it
was originally. In the kitchen, some of us still use compacters that
compress our garbage so we can cram more of it into the same space,
making it more manageable. With computers, it's our software that
takes up the space on our hard drives.
It used to be that our hard drives could only store a relatively
small amount of software, so space was at a premium. Compression
utilities such as DriveSpace and DoubleSpace were created to compress
software on the fly and effectively double the amount of software you
could store. But there were many problems with these utilities
including the fact that you could lose everything on your hard drive
if some part of it became corrupted. These programs have all but
disappeared primarily because today's multi-gigabyte hard drives
usually have plenty of space on them and if we need more, buying a
second high capacity hard drive is very inexpensive. Compression does
come in handy when it comes to storing data onto a single CD. A CD
typically holds around 650 megabytes. Compressing the data lets you
store a lot more information on a single disc.
Most of the compression we use on our personal computers basically
deals with four categories. They are music, photographic, video and
computer data. But technically it's all digital data, the language of
computers which is all zeros and ones. And while we still use
compression to save space, it's main application is to save time. When
exchanging files online, the smaller the file, the more quickly it
gets transferred. Along with email, the sending and receiving of
software online is one of the primary activities. Say you have a
digital picture you took with your camera and you want to send it to
someone. That picture may be several megabytes in size. Even if you
have high speed Internet access such as DSL or cable modem, it might
still take some time to send it to another location. And if you only
have telephone dialup service, it could take literally hours to send.
Photographs have an industry compression standard known as JPEG. These
compressed files usually have the suffix dot jpg (.jpg) after the
filename. Most photo-manipulative programs such as PhotoShop will let
you create a jpeg from your photographic image file. So since a jpeg
file is typically several times smaller that the original image,
you'll be able to transfer that digital photograph a lot more quickly.
One of the most popular audio compressions is MPEG-3. Music files
compressed using this standard contain the suffix dot mp3 (.mp3) after
the filename. When it comes to audio, a CD can store around 13 songs.
Using mp3 compression, a single CD can hold well over 100 tunes, and
transferring them online can save you hours.
But with any file you send or receive, be it a program, a word
processing document or any kind of data, compressing it down in size
will expedite its transference. Chances are that if you see a file
available for downloading on America Online or some web site, it's
already been compressed.
To compress an application or data file, you have to decide what
compression method you will be using. On the Windows side, one of the
more popular compression schemes is the Zip compression. Files that
have been zipped usually end with a dot zip (.zip) suffix after the
filename. On the Macintosh side, the most popular compression scheme
is called Stuffit and uses the dot sit (.sit) suffix after the
filename. To unzip or unstuff a file, you need to download one of the
many free utilities to do so. Most of the popular compression schemes
offer some sort of free decompression utility mainly because forcing
someone to buy something before they can use your data is generally
not a good idea.
If you plan to create compressed files, chance are you will have to
buy a commercial or shareware program. These compression utilities
offer many extra features such as treating compressed files as though
they were already decompressed. In many cases, you can actually view
the contents of a compressed file without having to actually
decompress it. These programs also let you make self-expanding or
self-extracting compressed files that expand automatically by double
clicking them without the need for any decompression software. This
method insures that whomever receives your compressed file will be
able to immediately decompress it without the bother of having to
locate a free decompression application.
Some companies and their compression products are PKWARE's "PKZip"
available at www.pkware.com, "WinZip" at www.winzip.com, and "ZipMagic"
from Aladdin Systems at www.aladdinsys.com. By the way, Aladdin also
publishes the Stuffit compression standard which is the one most
widely used by the Macintosh platform. "Stuffit Deluxe" is available
for both Macintosh AND Windows systems and the program works with all
of the popular forms of compression including zip, sit, binhex and
others. Check the web sites of all these companies for different
versions and pricing.
So there you have it. Compression makes your files smaller so they
take up less room on your hard drive or a CD, and it makes the sending
and receiving of your files more efficient. These days, getting more
done in less time is what compression is all about. |
