Castellini on Computers: Technology Watch

Most of us still struggle with the metric system. Then in the 90's we were thrown into a completely new way of measuring things...this time digital. It can be very confusing when working with computers if you aren't sure of the lingo. This month in our Technology Watch feature, you will learn how to make sense of these digital measurements and how they affect what you do with your computer.

In this first installment, let's start with the measurement of digital storage. The smallest unit of storage on a computer is a byte (actually 'bits' are smaller yet, but I'm not going there in this article). A byte is the equivalent of one character. For example, the word it takes up two bytes of space. The numeral 5 takes up one byte of space and the numeral 146 takes up three bytes of space. Speaking of space, spaces between words are considered characters. So a single space occupies one byte of space. Making sense yet?

Now let's grow those bytes into there larger brethren kilobytes. Normally a kilo equals 1000, but in the binary (digital) world, a kilo equals 1024. Thus a kilobyte (Kb) measures out to be 1024 bytes or 2 to the 10th power (2¹⁰). A megabyte is 2²⁰ or 1,048,576 bytes. And a gigabyte is 2³⁰ or 1,073,741,824 bytes.

In practical terms, a standard 3 1/2 floppy disk holds 1.44 megabytes of information. This translates to approximately 3000 typed pages, one high resolution photo, or about ten low resolution photos.

In contrast, a CD holds 650 megabytes of information... 1.3 million typed pages, 500+ high resolution photos and nearly 4500 low resolution photos.

Now let's talk pixels. Pixels measure the height and width of digital images and the resolution or clarity of out computer monitors. Pixel stands for "picture element" and represents a single point in a digital picture or image.

Similar to measuring the size of a photograph in inches, digital images are measured in rows of pixels (width) and columns of pixels (height) .

As you might guess, the larger numbers are capable of displaying larger images on a monitor. In other words, if you have a digital photo that is 730 X 550 pixel, you would have to scroll both horizontally and vertically on a computer displaying 640 X 480, but it would fit in the screen with no scrolling at 800 X 600 or above. Note the comparisons below:

This photo is being shown at normal size (no zooming). It is a digital photo from a one mega pixel camera (1152 X 864 pixels):

This example dramatically illustrates why it is important to resize photos for email. When taking pictures with a digital camera or scanning a photo, if the photo isn't resized, then the recipient may not see the whole picture AND the larger the photo the more room (bytes) it occupies which slows down transmission.

Study this chart for a general understanding of how the size of a photo relates to the space it occupies:

Photo Size (pixels)	File Size (bytes) jpeg format
400 X 300	~ 75 kilobytes (kb)
640 X 480	~ 150 kb
800 X 600	~ 230 kb
1152 X 864 (one mega pixel camera)	~ 350 kb
1600 X 1200 (two mega pixel camera)	~ 2000 kb (2mb)
2048 X 1536 (three mega pixel camera)	~ 2600 kb (2.6 mb)

Scanning images can produce file sizes that approach 50 or more megabytes if scanned at high resolutions.

In the previous section, we discussed the concept of screen or image resolution as they relate to pixels. Again, a pixel represents a single color (any one of millions of colors or shades of colors) or portion of our screen or image. In this section, we will explore printer resolution and how it relates to the screen resolution discussed above.

Today's printers measure the quality of the images/text they can produce in DPI (dots per inch). Since printers usually have four colors (black, yellow, cyan, and magenta), the printer has to use combinations of these colors to reproduce a single color we see on our screens. Therefore, the printer squirts out many 'dots' of ink per pixel of screen resolution.

So, when you read the theoretical maximum resolution of a printer, scanner and/or camera, take into consideration the following information:

Maximum printer resolution	Recommended Image (scanner) resolution
300 dpi	60 to 120 dpi
600 dpi	120 to 240 dpi
1200-1440 dpi	240-480 dpi
2880 dpi	500-700 dpi

Again, remember that the printer has to reproduce a single pixel of an image with as many as ten to fifteen drops of ink and use a complex mathematical "guess" (called dithering) to simulate the pixel of the image it is printing. So a scanner that can produce a 2400 dpi image doesn't do you any good at all with any of today's printers. These high resolutions are meant for commercial print quality photos for advertising or magazine layout.

Printer resolution depends greatly on the type of media you are printing on as well. So check your manuals for details about what paper types produce what types of resolutions.

One last thing to keep in mind as well is that the higher resolution an image is scanned or saved in, the larger the amount of space (bytes) it will require.

If you are in the market for a digital camera, this handy chart will help you select the one most appropriate for your needs:

Final Output Needed	Camera Type	Cost
small web (or email) picture or business card sized print	640x480	less than $100
4x6 print	1 megapixel	$175-200
8x10 print	2 megapixels	$350-500
11x14 print	3 megapixels	$700 and up

Let's leave the world of bytes and pixels (sort of) and talk about Internet speed. As we start using the Internet more and more for things like banking, research, shopping, and even entertainment, getting the information faster becomes paramount.

Speed, in the Internet sense, is measured in kbs (kilobits per second). When you download a form or software from the Internet, the measurement you are seeing is k/s (kilobytes per second). Ok, so I lied about getting away from the bytes thing...sorry about that.

When it comes down to the details, we don't care how many bytes, bits or rats are flying through our computer, we just want to see the end result...our information!! Study the following table for a few minutes and then read onward for further details:

Service*	Speed (kbps)	Time to view the CNN web page	Time to download an average song (4.5 megabytes)
Dialup modem (local provider, AOL, etc)	28.8 to 56	45-90 seconds	16-32 minutes
Cable Service (AT&T, Roadrunner, etc)	300-2000	3-8 seconds	1:30-2 minutes
DSL (Qwest, local provider)	300-8000	2-8 seconds	1-2 minutes
T1 line (typically used in large businesses or for Internet providers)	1000-1500	1-5 seconds	40-100 seconds
T3 line (known as the 'backbone' to the Internet)	up to 45000 (44.7 Mbps)	blink of an eye!	can download the entire Netscape or Internet Explorer program in less than 30 seconds!!

*Satellite Internet access comes in many flavors, but most closely resembles an entry level DSL connection.

This table should give you a practical idea of how speed affects your experience on the Internet. Most Internet users connect via a phone line and one of the most common questions revolves around "why my 56K modem only connects at 26,400 or 28,800". Here are the obstacles our modems must hurdle to gain a connection to the Internet:

First let's look at the local connection. When you click on the Dial or Connect button from your computer, our modems dial a phone number that we programmed in to connect with our local provider's server.

Time out: I've mentioned server a few times already, let me define it. A server is simply a specialized computer that directs incoming traffic from outside computers, provides security, and a few other functions behind the scenes.

When we start to connect to our provider, we hear the screeching and scratching of the two computers negotiating (a.k.a. handshaking). Once the handshaking finishes, the provider's server authenticates us (checks our user name and password), then finally lets us 'online'.

During the handshaking process, the two computers try to figure out the optimum speed at which they can talk to each other. This speed is determined by many things including but not limited to:

Wow, what a month for Technology watch. We hope you are enjoying this feature and the in-depth information we cover. You can learn more about this topic and any computer related topic by visiting my favorite technical dictionary...Webopedia.