The PC's Metric System - 1024 is a kilo - huh ??

When is a kilo not a kilo  .  .  . with computers. 

Computers use the binary system, so why would they bother with base 10 metric system terminology such as kilo and mega ??  Well, they had to have a way to denote large blocks of data, and that is what they decided to do - use the old metric units with a binary system.  Let me tell you this - it has caused one heck of a lot of confusion ! ! !

PC's deal with huge numbers of bits and bytes, and therefore quasi-metric terms have been assigned to the larger values.  One thing that is very odd about the computer version of the metric system for measuring large blocks of bytes, is that since the system is binary, it does not follow traditional metrics.  For example, a kilo has always meant 1000 in the decimal system.  Since PC's work with binary values, their memory and storage uses binary values - and therefore it was decided that kilo would be assigned to a binary value which would have a single "1" in it - and still keep the value as close to the decimal value as possible.  Hence, kilo in binary is equivalent to 1024 in decimal, or simply 2 to the 12th power, which in binary is 100000000000.  Similarly, the term Mega is 1 million is decimal, but in the computer world it is 1024 kilos, or :

1024x1024 = 1,048,576

  .  .  .  and Giga = 1024 x Mega, and Tera = 1024 x Giga  (Tera is the largest unit you will see)

Still we often use these terms loosely, and in conversation toy may hear someone refer to a thousand bytes (kB, or kilobytes), a million Bytes (MB, or Mega-Bytes), a billion bytes (GB, or Giga-Bytes), and a trillion bytes (TB, or Tera-Bytes).  Just remember to replace 1000 with 1024 for all these measurements.

Basically, this only applies to file sizes in bytes and storage.  You rarely see these terms applied to bits (i.e. Mbits, etc.).  In fact, now that we have discussed bits and bytes in the previous section, you can say goodbye to bits as far as storage, and you will very rarely ever see them mentioned again, until we get into speeds of data transmission - which is almost always measured in bits per second (never bytes).  For storage concerns, bits are just too small, and we can't really represent much at all with a bit, so PC storage lingo involves bytes, kilo-Bytes, mega-bytes, and giga-bytes.

Calculating the actual number of Bytes - Examples
24 kB, in actual bytes = 24 x 1024 = 24,576 bytes. 
24 MB = 24 x 1024kB = 24 x 1024 x 1024 
24 GB = 24 x 1024 MB = 24 x 1024 x 1024 x 1024
24 TB = 24 x 1024 GB =  24 x 1024 x 1024 x 1024 x 1024

However, you should never need to convert back down to bytes like this.  Leave the units as they are, in large blocks - that's what everyone uses with storage values anyway.