SHCC WYSIWYG Article from May 2012

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This article was written by Don VanSyckel, the club president, as a part of "The President's Pen".  This article appeared in the May 2012 WYSIWYG newsletter.

Disk Space

by Don VanSyckel

So with hard drives peaking into the terabyte range and thumb drives well into the gigabyte range, I thought I'd ask "Gigabyte? What is it and what's next?" Also how does reality meet up with hard drive spec's?

Everything in real life including money is measured (or counted) in 10's. When computers came along it was noted that 2^10 is 1,024, almost a even 1,000. For those not familiar with the notation, the circumflex (^) means "to the power of". So 2^10 = 2 X 2 X 2 X 2 X 2 X 2 X 2 X 2 X 2 X 2 = 1024. Memory, disk space, and everything else in computer is addressed with address lines or the address bus of the computer. Each address line can be a logical one (1) or a logical zero (0) or each address line has two possible values. So all storage is talked about in terms of 2 to the power of something. For example a byte of data is eight bits and can represent 2^8 = 256 different values or zero (0) to 255.

Disk space and memory long ago have grown through the kilobyte range. The next measure is megabyte which is 1024 kilobytes. Things kept growing and 1024 megabytes is a gigabyte. Computer memory is now measured in gigabytes, generally 2 to 4 for home PCs, thumb drives are measured in gigabytes generally 1 to 16, and hard drives are measured in gigabytes generally 200 to 1000.

So what's after a gigabyte? 1024 gigabytes are a terabyte. Here's a table that summarizes the progression:

NameSymbolBinaryDecimalName
kilobyte(KB)2^1010^3Thousand
megabyte(MB)2^2010^6Million
gigabyte(GB)2^3010^9Billion
terabyte(TB)2^4010^12Trillion
petabyte(PB)2^5010^15Quadrillion
exabyte(EB)2^6010^18Quintillion
zettabyte(ZB)2^7010^21Sextillion
yottabyte(YB)2^8010^24Septillion

So you can see that people have planned far in advance for terabyte, petabyte, exabyte, zettabyte, and yottabyte. Lest you think we'll blow through these too quickly I'll point out here that I believe most people reading this could easily fit all their digital stuff (programs, data, photos, and whatever) into a terabyte disk drive. (Please note I used the phrase most people so as to not get an argument from that one person who takes 500 high res digital photos every day and saves them all.) So to get to a yottabyte of storage you would need a trillion terabyte hard drives or some combination there of. Right now even with extra disk controller cards you can't get anywhere close to connecting a trillion hard drives to a PC. Even if you wait for petabyte hard drives you still need a billion disk drives to reach a yottabyte.

A kilobyte is actually 1024 and not 1000 even; a kilobyte is 2.4% larger than 1000. Then each step up the ladder another 2.4% is introduced. These are compounded like interest, not added. When a gigabyte is reached a gigabyte is 9.9% larger than a corresponding billion. When (or maybe if) a yottabyte is reached it will be 20.9% larger than the corresponding Septillion. Where this becomes confusing is with the hard drive manufacturers. In an attempt to make their product be all that they want it to be the manufacturers use the word gigabytes where what they really mean is "billions of bytes". So by the time the hard drive is formatted and some of the space is lost to the formatting and then another 9.9% is lost due to the gigabyte to billion conversion, a hard disk can be quite a bit smaller in real gigabytes than what the box claims. Read some of the packaging of hard drives at the store, I've seen some where they actually state "gigabyte = 1,000,000,000 bytes".

End of Article

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