As a side issue, I have an Xbox 360 and haven't bought GTA 5 as I only have a 4gb hard drive and you need 8gb. I believe it is possible to play this on my console if I plug in a 8gb flash drive, as long as it is formatted for xbox 360 is this true? And if so, how do you format it?
Also do the ps4 and Xbox one have to be online? Or can you use them as standalone games consoles still?
The file system is FAT32, you can format a disk via windows explorer (or the command line.)
GTA5 probably writes data to the hard drive as at can be streamed faster from there than straight from the DVD.
EDIT: just found this http://support.xbox.com/en-GB/xbox-360/accessories/usb-flash-drive