31
Gane and Sarson
(G & S)
Symbol Set
Description
Yourdon Symbol Set
Data
Source
and
Destination
symbol
depicts external entities or portrays source
and destination of data flow.
Bubble/circle symbol may represent the
whole
system (context diagram),
internal
entity
(physical
DFD)
or
process
(logical
DFD) of a particular system.
Storage symbol
represents data storage
where data are being stored.
It
can
also
represent
a
view
or
portion of
company’s database.
or
Data flow symbol indicates a flow of data
or
documents
into
or
outside
from the
system;
flow
of
data
between
the
entities
(in physical DFD) and flow of data
between processes (in logical DFD).
or
Figure 2.4 Four Basic Elements of DFD
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