The computer equivalent of human memory is its storage system, which can
consist of a hard drive, a floppy disk drive, a CD or DVD drive, and a few
other forms of electronic filing cabinets. Here is where the machine may have
a bit of advantage over humans. A computer’s storage capacity is essentially
limitless; you can keep adding more and more disk drives, or creating more
and more CDs or DVDs, or connecting to the Internet, which is expanding
almost without limit. I discuss storage systems in Chapters 7, 8, and 9. Your
computer’s brain is its microprocessor. This electronic circuit manipulates
data based on rules and instructions. Though not all that smart, it is very
fast, and that makes a great deal of difference.Now just to make things confusing to humans, sitting in between the com-
puter’s storage system and the microprocessor is its computer memory,more
properly referred to as random access memory (RAM).The computer gets its
work done here: Think of it as the scratchpad, the building block, the assembly
place for your words, numbers, pictures, and sounds before they are displayed,
printed, or put in the file for future reference. The most important thing to
remember about RAM is that it’s volatile,or temporary, memory — quick,
capacious, and relatively inexpensive but requires a near-continuous source
of electrical power and regular refreshing of its contents. Put another way:
Turn off the laptop, and RAM loses its memory.It’s also important to understand exactly what random accessis and see how
it differs from storage.Think of RAM as if all of the information your computer
is working on is spread out on a large tabletop — a very, very large tabletop,
perhaps more like an aircraft carrier. This type of memory is called random
accessbecause the computer’s brain — the microprocessor — is capable of
reaching directly into RAM to retrieve a specific piece of information or
instruction. Your computer’s very smart processor has an index that tells
what’s on the table and its exact location; that’s random access. Compare
that to data stored on a rotating hard drive. On that sort of system, the
drive’s read/write head has to wait until the block bearing the information
moves into position beneath the head.Even slower is data stored on a sequentialmedia like a tape cartridge; here
the system has to wait until the tape physically moves from one reel to
another to a particular spot. If one section of a piece of data is at the begin-
ning of the tape and the other is at the end, there can be a significant lag in
retrieval. Why, then, use sequential media? The only good reason for modern
systems is to store backups of huge files or make ongoing backups of real-
time transactions like those from a bank or a stock exchange.You may have noticed that no computer really duplicates a mind... except
that some deep (human) thinkers believe we’re approaching the point at
which a machine can begin making independent decisions. Today a machine
can “remember” information, make decisions based on very complex sets of78 Part II: Explaining What Could Possibly Go Wrong