Wednesday, June 29, 2011

How Much Data Is That?

How Much Data Is That? - - - Close up photo of a tape measure - - - Original photo copyright Brian Evans - - - Licensed through iStockphoto.com


Note: The information shown below uses measures only associated with data. For example, a kilo-anything is 1000 . . . except that when it is a kilobyte, it is 1024, an even power of two.  

Whenever we discuss quantities of data, we tend to do it in the abstract. We speak of a kilobyte, or a megabyte or a gigabyte without really knowing what it represents.
The following table shows various quantities of bytes, in each power of ten. Usually, they are shown with multiples of 2 and 5 also. For example, 1 Kilobyte, 2 Kilobytes, 5 Kilobytes.
All the examples are approximate and are rounded. For example, a computer card has 80 columns. If 50 columns contain data on a card, then two cards will be 100 bytes. Also, a 3-1/2 inch diskette can contain 1.4 Megabytes. Showing it as 1 Megabyte reflects both (a) the diskette not typically being filled and (b) rounding. Finally, a CD-ROM can hold more than 500 Megabytes. However, it is listed at that level as "typical" and as the closest match.
Bytes (8 bits)
  • 0.1 bytes: A single yes/no decision  (actually 0.125 bytes, but I rounded)
  • 1 byte: One character
  • 2 bytes:
  • 5 bytes
  • 10 bytes: One word (a word of language, not a computer word)
  • 20 bytes:
  • 50 bytes:
  • 100 bytes: Telegram; two punched computer (Hollerith) cards
  • 200 bytes:
  • 500 bytes:
Kilobyte
     1,024 bytes; 210;
     approx. 1,000 or 10
 3
  • 1 Kilobyte: Joke; (very) short story
  • 2 Kilobytes: Typewritten page
  • 10 Kilobytes: Page out of an encyclopedia
  • 20 Kilobytes:
  • 50 Kilobytes: Image of a document page, compressed
  • 100 Kilobytes: Photograph, low-resolution
  • 200 Kilobytes: Two boxes (4000) punched computer (Hollerith) cards
  • 500 Kilobytes: Five boxes, one case (10,000 of punched computer (Hollerith) cards
Megabyte
     1,048,576 bytes; 220;
     approx 1,000,000 or 10
 6
  • 1 Megabyte: Small novel; 3-1/2 inch diskette
  • 2 Megabytes: Photograph, high resolution
  • 5 Megabytes: Complete works of Shakespeare; 30 seconds of broadcast-quality video
  • 10 Megabytes: Minute of high-fidelity sound; digital chest X-ray; Box of 3-1/2 inch diskettes
  • 20 Megabytes: Two boxes of 3-1/2 inch diskettes
  • 50 Megabytes: Digital mammogram
  • 100 Megabytes: Yard of books on a shelf; two encyclopedia volumes
  • 200 Megabytes: Reel of 9-track tape; IBM 3480 cartridge tape
  • 500 Megabytes: CD-ROM
Gigabyte
     1,073,741,824 bytes; 230;
     approx 1,000,000,000 or 10
 9
  • 1 Gigabyte: Paper in the bed of a pickup; symphony in high-fidelity sound; broadcast quality movie
  • 2 Gigabytes: 20 yards of books on a shelf
  • 5 Gigabytes: 8mm Exabyte tale
  • 10 Gigabytes:
  • 20 Gigabytes: Audio collection of the works of Beethoven; five Exabyte tapes; VHS tape used to store digital data
  • 50 Gigabytes: Library floor of books on shelves
  • 100 Gigabytes: Library floor of academic journals on shelves; large ID-1 digital tape
  • 200 Gigabytes: 50 Exabyte tapes
Terabyte
     1,099,511,627,776 or 240;
     approx. 1,000,000,000,000 or 10
 12
  • 1 Terabyte: Automated tape robot; all the X-ray films in a large technological hospital; 50,000 trees made into paper and printed; daily rate of EOS (Earth Orbiting System) data (1998)
  • 2 Terabytes: Academic research ligrary
  • 10 Terabytes: Printed collection of the U. S. Library of Congress
  • 50 Terabytes: Contents of a large mass storage system
Petabyte
     1,125,899,906,842,624 bytes or 250
     approx. 1,000,000,000,000,000 or 10
 15
  • 1 Petabyte: 3 years of EOS data (2001)
  • 2 Petabytes: All U. S. academic research libraries
  • 20 Petabytes: 1995 production of hard-disk drives
  • 200 Petabytes: All printed material; 1995 production of digital magnetic tape
Exabyte
     1,152,921,504,606,846,976 bytes or 260
     approx. 1,000,000,000,000,000,000 or 10
 18  
  • 5 Exabytes: All words ever spoken by human beings.
Zettabyte
     1,180,591,620,717,411,303,424 bytes or 270
     approx. 1,000,000,000,000,000,000,000 or 10
 21
Yottabyte
     1,208,925,819,614,629,174,706,176 bytes or 280
     approx. 1,000,000,000,000,000,000,000,000 or 10
 24


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