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Measurements
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b = bit = 0
or 1
B = byte = 8 bits
kb = kilobit = 1024 bits
KB = Kilobyte = 1024 bytes
MB = Megabyte = 1024 Kilobytes
GB = Gigabyte = 1024 Megabytes
TB = Terabyte = 1024 Gigabytes
PB = Petabyte = 1024 Terabytes
EB = Exabyte = 1024 Petabytes |
KB, MB, GHz, and All of
That Stuff
In case you haven't
noticed (fat chance), the computer biz is filled with words that
start with "kilo" and "mega", and abbreviations like "K" and "M"
and "G". These words and abbreviations don't represent "things".
Rather, they represent numbers. Kind of like the old gangster
movies where a bad guy would say fifty g's rather than
fifty thousand dollars. Computer nerds use a different slang
for numbers. But the idea is the same.
K. M, and G are Numbers
Let's start with just the
numbers -- the K and M and G part. We'll talk about the "B" and
"Hz" and stuff in a moment. Table 1 shows what the abbreviations
mean, how they're often spoken, the approximate number each
represents, and the way-too-trivial-a-difference-to-worry-about
actual number each represents.
| Abbreviation |
Stands for |
Spoken as |
Approximate
# |
Actual # |
|
K |
Kilo |
kay or killa |
1,000 (a
thousand) |
1,024 |
|
M |
Mega |
meg |
1,000,000 (a
million) |
1,048,576 |
|
G |
Giga |
gig or giga |
1,000,000,000 (a billion) |
1,073,741,824 |
Table 1 |
If you ignore the
boring "actual" numbers, you'll see there's a simple pattern
to it. Each time you go to from K to M to G, you stick
another ,000 onto the end of the preceding number (also
known as multiplying the previous number by a thousand), as
you can see below:
-
1,000 K (kilo)
-
1,000,000 M (mega)
-
1,000,000,000 G (giga)
So "K" means
"thousand" or ",000", and "M" means "million" or ",000,000"
and G means "billion" or ",000,000,000". Though maybe I
should just shut up now before I make it sound more
complicated than it is. Suffice it to say if you're gonna
buy a used car, and it has 80K miles on it, then that means
the car has 80,000 miles on it. If the car has 20M or 20G
miles on it, don't buy it.
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B is for Byte
Information in your
head doesn't have any particular "size" to it. Just because
Albert Einstein was a genius doesn't mean his head was the
size of hot-air balloon or the Good Year blimp. His head was
probably about the same size as anyone else's, give or take
a couple inches. That's because the human brain stores
information in some really weird abstract way that nobody
understands.
Computers have no
brains, and really don't store "information" the way a human
brain does. In fact, computers don't really store
"information" per se. Except in the sense that a book stores
information -- as letters, numbers, pictures, and words. The
information in a book has no meaning to the book. Likewise,
the information in a computer has no "meaning" to the
computer. Books and computers are a lot alike in that way --
they both can be used to store text, numbers and pictures.
And they're also alike in that the text, pictures, and
numbers inside have no "meaning" to either the book or the
computer.
Anyway, the point is
it takes a certain amount of "space" to store information
outside of our brains. That's because the information needs
to be stored as words, numbers, pictures, or something that
takes up space. In a computer, the basic "unit" of measure
is a byte, which is the amount of space it takes to
store one character, like the letter "A" or an exclamation
point (!). So it takes exactly three bytes to store the word
"cat". It takes about 2,000 bytes to store one double-spaced
page of typed text.
When you see an
uppercase letter "B", that stands for "byte". So instead of
saying it takes "three bytes" to to store the word "cat", I
could have said it takes about 3B to store the word "cat".
Likewise, I could have said it takes about 2,000B to store
the a typed page of text. So now, given all you know about K
and M and G, I bet you can figure out what KB. MB, and GB
mean before you even peek at Table below
| Abbreviation |
Stands for |
Approximate
# |
(or) |
Actual # |
|
KB |
Kilobyte |
1,000 bytes
|
A thousand
bytes |
1,024 bytes |
|
MB |
Megabyte |
1,000,000
bytes |
A million
bytes |
1,048,576
bytes |
|
GB |
Gigabyte |
1,000,000,000 bytes |
A billion
bytes |
1,073,741,824 bytes
|
Table 2
|
So before, when I was
talking about a typed, double-spaced page of text taking up
about "two thousand bytes" or "2,000B", I could have said it
take about 2 KB to store that
page of text. Often, the "B" is assumed, so it would be just
as accurate for me to say it takes about
2 K to store that page.
Figure 1
The first file in in
Figure above has a size of 735 KB, (or roughly 735,000
bytes). The biggest file in that folder is 1,732 KB. That
could actually be expressed as 1.7MB (because a megabyte is
about 1,000 kilobytes). But Windows always shows the file
sizes in kilobytes (KB) just to keep all the numbers on the
same scale.
Of course, not all
information in a computer is typed text. A computer can also
store pictures, sound, and video. We generally refer to
pictures, sound, and video as multimedia or media
files. But like typed text, those files have sizes too.
Table 3 provides some examples of multimedia files.
| Example |
Size |
Or about... |
| The picture shown in
Figure 1 |
61 KB |
61,000 bytes |
| This entire Web page
you're reading |
125 KB |
125,000
bytes |
| A 3-minute CD-quality song |
3.5 MB |
3,500 KB or
3,500,000 bytes |
| 1 minute of DVD-quality
video with sound |
11 MB |
11,000 KB
or 11,000,000 bytes |
Table 3
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Exactly how much
"stuff" you can get on a disk depends on the capacity
of the disk. This is no different from the capacity of a
container for water (e.g. cup, bucket, bathtub). But of
course, we don't use "pint", "quart", "gallon" and such for
describing disk capacities. We use (what else?), KB, MB, and
GB.
There are lots of
different "types" of disks out there. You've probably
already heard of most of them -- floppy disks, CDs, DVDs,
and of course the hard disk that lives inside every
computer. Hard disks come in many different sizes., usually
in the range of 20GB to 120GB. Table 4 lists the storage
capacities of common types of disks. The column on the right
describes the capacity in relation to the capacity of a
floppy disk, just to give you some perspective on how
greatly these capacities vary.
| Disk type |
Capacity |
Equals this
many floppy disks |
| Floppy disk |
1.4 MB |
1 |
| CD |
700 MB |
700
|
| DVD |
4.7 GB |
4,700 |
| Hard disk |
20 GB to 120
GB |
20,000 to
120,000 |
Table 4
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bps is for "bits per
second"
The letters bps
are short for bits per second. A byte (described
earlier) is actually 8 bits. But that's not important.
What's important is that unlike a byte, which is a measure
of size, bps is a measure of speed. Simply stated,
the higher the bps, the less time it takes. It's a lot like
Miles Per Hour (MPH) in that sense. Think how long it would
take to get from New York to California in a car going
55MPH. Now think how long that same trip would take in a jet
going 700MPH. Simply stated, the higher the MPH (or bps),
the less time it takes.
As a rule, we use
bps as a measure of the speed of getting data from one
computer to another across a network (including the
Internet). And we use "K" for a thousand, "M" for a million,
and "G" for a billion, as usual. Table 5 sums it all up. The
fourth column shows some alternative abbreviations. The
rule-of-thumb is that an uppercase B always stands for
"bytes" while a lowercase "b" always stands for "bits per
second".
| Abbreviation |
Spoken |
Bits per
Second |
(English) |
Alternative
Abbreviations |
| Kbps |
Kilobits |
1,000 |
Thousand |
Kb or
Kbits |
| Mbps |
Megabits |
1,000,000 |
Million |
Mb or
Mbits |
| Gbps |
Gigabits |
1,000,000,000 |
Billion |
Gb or
Gbits |
Table 5
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The most common use for
the bps measurements is in types of Internet accounts. To give
you a sense of how the speeds relate to one another in terms of
"wait time", Table 6 compares the amount of time it would take
to download (copy) a 1MB file from a computer on the Internet to
your own computer. (Since a byte is equal to 8 bits, a 1 MB file
is roughly 8,000,000 bits.) Also, I'm using "Broadband" as a
general term for Cable and DSL accounts, which are actually
available in speeds ranging from about 256 Kbps to 1,000 Kbps.
Note, too, that 1,000 Kbps is the same as 1 Mbps.
| Account type |
Speed |
Bits per
Second |
Time to download 1MB |
| Dial-up |
56 Kbps |
56,000 |
143 seconds |
| ISDN |
128 Kbps |
128,000 |
63 seconds |
| Broadband |
1 Mbps
|
1,000,000 |
8 seconds |
| T1 |
1.5 Mbps |
1,500,000 |
5 seconds |
Table 6
Hz is for
Hertz
The Hz abbreviation
stands for Hertz, but has nothing to do with pain or
car rentals. In this context, "Hertz" pays homage to a guy
named Heinrich Rudolf Hertz who figured out that radio and
electricity have frequencies that you can measure in
cycles per seconds. But that's getting more technical
(and boring) than we need to be.
The workhorse of your
computer is its microprocessor - a little chip about
the size of a toenail that can work at a pretty fast speed.
Exactly how fast it can work is measured in terms of
"instructions per second", which roughly corresponds to
Hertz's idea of frequency. Of course, microprocessors can do
thousands, millions, or billions of instructions per second.
So that brings good old K, M, and G into the picture once
again, as summarized in Table 7.
| Abbreviation |
Stands for |
Cycles per
Second |
That is... |
| KHz |
KiloHertz |
1,000 |
Thousand |
| MHz |
MegaHertz |
1,000,000 |
Million |
| GHz |
GigaHertz |
1,000,000,000 |
Billion |
Table 7
As is always the case
with speed, "faster" means "less time waiting" for a human.
The speed of the processor only affects "local tasks". It
has nothing to do with how long it takes to get your e-mail
or download stuff from the Internet. The speed of your
Internet connection is all that matters there. The speed of
your microprocessor has more to do with how long it takes to
render changes to huge graphic images, or produce movies, or
similar complex tasks that require a lot of internal
calculations on the computer's part.
So there you have it.
To summarize, K, M, and G are all abbreviations for numbers:
The letters that come
after are either a measure of size or capacity, or a measure
of speed, as follows:
-
B = Bytes
or "how much" information.
-
bps (or b) = "bits
per second" or "how fast across some wire"
-
Hz =
Hertz of "how many calculations can be done in
one second"
You're becoming
dangerously close to be a full-fledged computer nerd here...
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