Data storage

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. 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". 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.

Tip: Just in case you're some kinda math brain who's wondering where the actual numbers come from, K=2¹⁰, M=2²⁰, G=2^30.  (Yawn)

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 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 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 2.

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 takes 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.

If you already have files stored on your computer, and know how to get around in folders, you can see that every file has a size. You'll need to use the Details view (choose View > Details from the menu bar above the icons). Figure 1 shows an example where you can see the sizes of some pictures in a folder on my computer.

Figure 1

The first file in in Figure 1 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 a 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

E xactly how much "stuff" you can get on a disk depends on the capacity of the disk. This is no difference 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 size, 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