Video and audio can be recorded on a number of mediums such as tape, optical, hard disk, or high density memory chips (integrated circuits). Tape has been the preferred method of acquisition because of its storage capacity and cost. An edit suite will be defined by the format of its principal VTR machines, but will often be equipped with other VTR machine formats to allow transfer of acquisition material to the main editing format, or to provide lower quality copies for off-line editing or previewing.