Q: why does my 8gb ipod touch have 6.4 gb?

Because the current iOS version (5.1.1) takes up about 1-1.5 GB of storage.  This is because the software has to have a place to store the information and programs, therefore taking up some memory only for the software.

this is because the ipod has programs like ios and other software needed to run installed on it out of the box.There is no way to change this,but i have not run into a lack of memory yet.

My 8gb iPod touch is the exact same way, also my iPad is a 64gb, but only has a capacity of 57.2 gb for the same reason

Like most computers/devices:

How Mac OS X and iOS report storage capacity

Have you downloaded anything yet, that takes up memory such as music, applications, web browsing.

Actually iOS is the software and is not a program, it is the thing that makes the iPod run, for example, when you take the iOS software update file and unzip the folder, if you edit a file, the device will no longer work.