Kilobyte--Megabyte--Gigabyte

Dr. Kenneth Hoffman

A kilobyte equals 1000 bytes (actually 1024 bytes but we normally round it off). A megabyte equals 1,000,000 bytes. A gigabyte equals one billion bytes. For comparison, a standard 3 1/2 inch floppy disk holds 1.44 megabytes (1,440,000 bytes). A Zip disk holds 100 or 250 megabytes. CD-ROM disks hold 650-700 megabytes. A byte is the equivalent of one ASCII character like the letters I am typing now. So you can count up the number of bytes in this message by counting the number of characters on this page including spaces. The unformatted text on this page takes 2.4 KB as an ASCII file, but the MSWord Doc file takes 26 KB. (Just take away the KB and add 000, i.e., 2,400 bytes vs. 26,000 bytes.)

Graphics and media files are memory intensive. Much more so than ASCII text. A 1024x768 medium resolution digital image (pixels times the number of lines) containing 3 bytes of color information per pixel, allowing approximately 16.8 million colors per pixel, takes 2.4 MB of storage space (1024x768x3) in uncompressed form. Images from a digital camera saved with JPG compression take between .5 MB (low resolution image) and 2.5 MB (high resolution image). High resolution images that are not compressed take approximately of 11-18 megabytes. So, we can store sixty-six 15 MB images on a 1 GB drive. Since most computer hard drives hold anywhere from 20 to 80 gigabytes that sounds like a lot of storage space. But remember, multimedia projects also contain video and music in addition to images. A DVD disk holds 4.7 Gigabytes and will store one feature film plus some additional "extras". One minute of stereo audio requires 10 MB of file space. One minute of low quality video takes about 30 MB of file space.

When preparing images for the Web small file size is extremely important. No full-screen images--320x240 pixels or smaller is best. The number of pixels per inch should not be greater than the resolution of a display monitor--72 pixels per inch. No individual image should be larger than 50 kilobytes. If there are several images on a page then make them very small, less than 10 KB per image.

So, lets look at Bytes this way:

GB = Billion $$ -- 1,000,000,000

MB = Million $$ -- 1,000,000

KB = Thousand $$ -- 1,000

Byte = 1 $