Subject: Info: Metric Prefixes. From: Metric_Enquirer@ Sender: Metric_Enquirer@ I append http://www.berklix.com/~jhs/std/kilo.txt Going larger from 1 as in Megabyte 10^n 2^n Disc Sizes Silicon Memory Bytes 0 0 1 1 kilo k 3 10 1,000 1,024 Mega M 6 20 1,000,000 1,048,576 Giga G 9 30 1,000,000,000 1,073,741,824 Tera T 12 40 1,000,000,000,000 1,099,511,627,776 Peta P 15 50 1,000,000,000,000,000 1,125,899,906,842,624 Exa ? 18 60 1,000,000,000,000,000,000 1,152,921,504,606,846,976 Zetta Z 21 70 Yotta Y 24 80 https://en.wikipedia.org/wiki/Exabyte kilo is abnormal, it uses a small k often, all else above use capitals. Going smaller down from 1, eg milli as in millimetre cm,mm 10^-n Decimal Vulgar Fractions 0 1 deci ? -1 0.1 1/10 centi c -2 0.01 1/100 milli m -3 0.001 1/1000 as in milli second, ms micro u -6 0.000001 as in micro second, millionth of a sec. nano n -9 0.000000001 pico p -12 0.000000000001 femto f -15 0.000000000000001 https://en.wikipedia.org/wiki/Femto In the computer world: For silicon memory eg in a PC: K is 1024 M is 1024 x 1024 = 1048576 G is 1024 x 1024 x 1024 = 1073741824 bit/bytes/whatever Why 1024 & not 1000 ? (1024 comes from binary arithmetic: try multiplying 2 by itself till you get to 1024, not 1000 !) & why multiply 2's & not 3's ? Well digital computers are like switches, How many toggle type light switches do you know that work well & don't burn out if left half on/ half off ? Binary is On or Off, no half measures. Binary switches are easy to manufacture, reliable & cheap. 10 level light switches would be expensive, akin to the variable light switches in living rooms, which are expensive, hot, smell, & sometimes burn out. When you've got millions in a computer, you don't want them getting hot & unreliable. Disc manufactures however, stick to 1K = 1000 = 1K , not using 1024 = 1K Why? Well it's like the Americans with their small gallons (worth precisely 16/20th (*) of a British gallon). A cowboy's eight gallon hat wouldn't sound so good as what (perhaps used to be called) a ten gallon hat, would it ? Same for disc manufacturers, their discs sound slightly bigger if measured in multiples of 1000 times 1000 times 1000 bytes & not 1024 x 1024 x 1024 etc. If you were selling, would you prefer to call it a 60 Gig drive or a 64G drive ( 64424509440 = 60 x 1024 x 1024 x 1024 ). Why don't DRAM manufacturers do that trick too: Not so easy for them ! DRAM manufacturing scale factors are binary. You either squeeze all the gates smaller, & double the chip density again (that `binary base 2'again !), or you don't. Disc manufacturers by contrast have more variety, eg different circumferences on inner & outer tracks, differing density of tracks, & thus numbers of tracks, & number of surfaces on a disk drive etc, they end up with random numbers they round up or down a bit. Someone has a half terabyte in his PC ? Well it'll be of disc, not memory :-) Take about 10 x 50 Gig commodity IDE PC type drives & you have half a terabyte. Or take 2 of the new 250G drives. What would you use it for ? Well if you use Raid, with each disc having a spare copy in case the other dies, that divides your capacity by 2. So that's 250 Gig left. What to do with 250 Gig ? A friend drives a lot more than that for a company I know. But for home ? Bootleg videos I guess. Video capture of lots of TV channels would eat it up. My first personally owned computer had 5 Megabytes. The first computers I used, used paper tape & punch cards to store the data. On them you'd see physical holes for each Bit ! (*) Re 16/20: I guess the American forgot, maybe when the Mayflower went over, that though 16 solid ounces make a pound, it takes 20 fluid ounces to make an imperial pint, but they did remember it was 8 pints to the gallon :-) ( 1 pound = 454 grams, 1 ounce = 28.4 grams ) ---------------- HERE'S A NEW BIT ABOUT DIFFERENT SIZES ON USB STICKS v. DISCS it's rough, extracts of mail, to be sorted later: > Free space - 2,130,018,304 bytes, 1.98 Gb. Noted. Yes, Microsoft is there showing you how many bytes free within the DOS file system, after MS has taken a small amount for laying down a file system (akin to kerbs & stuff in a car park that take a little space, but needed to order all the car parking) Then that whole DOS file system lives within one of up to 4 partitions, that are indexed from an MBR a Master Boot Record. Here for example is the MBR off my Celldisk 256 M flash drive / stick: The data for partition 1 is: sysid 6 (0x06),(Primary 'big' DOS (>= 32MB)) start 32, size 262144 (128 Meg), flag 80 (active) beg: cyl 0/ head 1/ sector 1; end: cyl 256/ head 0/ sector 32 The data for partition 2 is: sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD) start 262144, size 237536 (115 Meg), flag 0 beg: cyl 256/ head 0/ sector 1; end: cyl 487/ head 30/ sector 32 The data for partition 3 is: The data for partition 4 is: Admittedly I changed the Celldisk stick, normally you'd just see partition 1 taking all the space on the stick. The OS takes away the largest chunk on a new single disk PC (not of course on 2nd extension disk though). The OS takes more than it needs at start too, cos when installed it normally goes in its own partition with a few gig spare, empty largely unusable for normal data. Then File systems overhead (those parking kerbs) takes a smaller bit (half a per cent in case of your 2G stick, as you have 2,130,018,304 bytes & a raw stick size was 2,138,177,536) then the MBR needs 512 bytes to a few K. Then there's the difference that disc drive manufactures sell discs to the theme of 1,000,000,000 bytes = 1 Giga byte of disc. Whereas in the rest of computing (eg RAM etc), 1 K = 1024 (= 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2) 1 M = 1048576 = 1 K x 1 K 1 G = 1073741824 = 1 K x 1 M So you'r up to 7% short there just on a Gig, depending which way its counted, apart from space for the OS There's no OS on a disc or flash stick when sold by manufacturer, either can have them installed on now that flash are big enough. There's not even a need for discs or flash to have an MBR on, or a DOS FS, but in practice all Flash are sold with an MBR & a pre formatted DOS FS (remember the old days when you could buy pre-formatted floppies, or raw & format yourself) Discs come with spare sectors that are automatically patched in when other sectors go bad, or are seen bad by manufacturer. (& there's no particular expectation of a power of 2 type sizing, as the disc has a variable number of platters, & there are more sectors on outer circumferences etc). Against that, the flash memory sticks are oblong chunks of silicon, & more of an expectation toward power of 2 type sizing, except it seems the manufacturers just patch out any bad blocks, & don't keep a few bad blocks in reserve to replace them with. http://www.berklix.com Computer Consultancy http://www.berklix.com/~jhs/cv/ My Resume - English & German http://www.berklix.com/~jhs/contact/ Contact - German for business also OK. http://www.berklix.com/free/ Free Software http://www.berklix.org Free Organisations & Clubs