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August 25, 2006
Thanks for the Memories
Dear Larry,
A few weeks back you discussed the difference between disk
space and memory, something that still confuses me to this day. Can you
elaborate please?
F. C.
Dear F. C.,
This still confounds many people and all too often someone
will refer to one when they mean the other. So once again, I’ll rely on
analogies to help elucidate the differences.
Consider your own short-term memory and long-term memory.
Stored in your long-term memory are the people, places, and events that occurred
in your early life. While you may think about some of these events from time to
time, many of these memories are dormant and only awakened occasionally. Now
contrast this with your short-term memory, the forefront of your mind where you
process all your day-to-day tasks. Stored here are all the telephone numbers you
frequently use, your memories about who you’re meeting for lunch tomorrow,
playing tennis with on Tuesday, the items you have to pick up at the store on
your way home, and don’t forget about your dentist appointment later in the
week. It’s where all of your active mental processing happens.
In this vein, your short-term memory represents what we call
memory in your computer and your long-term memory represents that computer’s
hard disk drive where your documents, spreadsheets, and financial records are
tucked away for safe-keeping. Your computer’s memory is only “on” when the
computer is turned on while the information and data on your hard drive remains
intact even when the PC is turned off. When you want to work on a Word document,
for example, your computer pulls the program files for Microsoft Word along with
the document you requested from the hard drive and copies them into the system’s
memory so that you can type in some new text, make some changes, or perhaps
print a copy of the document. Your computer does this, because as fast as your
hard drive can read and write lots of data, your computer’s memory works
significantly faster. When you close Word and save your changes, you’re telling
your computer to rewrite your document back to the hard drive and to free up the
memory space that it was using while you were working with the program. (Note
that the Word program files aren’t rewritten to the hard drive as they were
never changed; the only modifications that have occurred were those relating to
your document.)
Here’s a better analogy I like to use to distinguish between
hard drive space and memory. Your hard drive is like the filing cabinets in and
around your desk while the computer’s memory is the free space on top of your
desk where the work actually gets done. Say you want to work on your taxes; you
look in your filing cabinets and pull out the manila file folders you need
containing your tax information and transfer them to your desktop where you
actually perform your work. When you’re finished, you put the altered tax
folders back where they came from and move them from your desk to your filing
cabinet
Just like a computer, we too, can multitask, and sometimes
we’ll have tax folders on one part of our desk, office work on another, possibly
a desktop calendar off to the right, and a scratch pad sitting to the left.
Eventually, if we try to work on too much, our desktop will become overly
cluttered and we’ll have to file some stuff away to make more room. Your
computer works in much the same way. The more memory your computer has, the more
room is available for it to process multiple programs: your Word document, your
ongoing game of Solitaire that’s currently minimized, your antivirus software
that never stops running behind the scenes, and so forth. Ask your computer to
do too much at the same time, however, and it will start to bog down as it runs
low on precious memory. Eventually, your computer will have to move current data
back to the hard drive just to make temporary space for something else you’re
trying to do. When this happens, your PC is essentially extending your
computer’s memory onto the hard drive, a desperate measure indeed as this will
slow down processing even more.
No surprise therefore that as memory and hard drive prices
fall, newer computers ship with more of each. A typical desktop computer that
was manufactured three years ago probably shipped with 256 megabytes of memory
and 40 gigabytes of hard drive space. The average computer today comes with a
gigabyte of memory (4 times the 256 from three years ago) and easily double the
hard drive space. After all, you need the storage capacity to hold all those
picture and music files!
This is Larry Schneider, logging off.
