Recently I had to use the latest BlackArch ISO '2017.06.14' which is approximately 7.1GB on a laptop equipped with only 2GB of RAM to reset a Windows passwd and run some tests.My question is how is this possible with the ISO being far larger than the amount of RAM installed?  What's the difference between an installed to HDD system loading files into RAM vs a live boot from USB 2.0?Apologies if this is has been asked before or if it is fairly trivial. 
ISO size vs RAM for live boot
linux;usb;iso;ram