A Data Store symbol is where data "rests" when it is neither flowing nor being operated on. A data store can be a database, hard disk or a file on a disk. The Gane & Sarson methodology uses a rectangle open at one end; the Yourdon/DeMarco methodology and real time diagrams, such as a DFD Ward & Mellor, use two parallel lines (or a rectangle open at both ends).
Data Stores are defined with the names of data elements and data structures, which can consist of any characters. If a character other than the upper or lowercase letters A through Z are part of the name, the entire name must be enclosed within double quotes.