1. Data Flow Diagram Notations
Dataflow Dataflows are pipelines through which packets of information flow. Label the arrows with the name of the data that moves through it.
Data Store Data stores are repositories of data in the system. They are sometimes also referred to as files.
Process A process transforms incoming data flow into outgoing data flow.
Yourdon and Coad Process Notations
Gane and Sarson Process Notation
Yourdon and Coad Datastore Notation
Gane and Sarson Datastore Notations
External Entity External entities are objects outside the system, with which the system communicates. External entities are sources and destinations of the system's inputs and outputs.

2. DataFlow Diagrams

3. Data Flow Diagram LayersDraw
Data flow diagrams are drawn in several nested layers
A single process node on a high level diagram can be expanded to show a more detailed data flow diagram.
Draw the context diagram first, followed by various layers of data flow diagrams.

4. DFD Layers

5. Context Diagrams
A context diagram is a top level (also known as Level 0) data flow diagram. It only contains one process node (process 0) that generalizes the function of the entire system in relationship to external entities.

6. DFD levels
The first level DFD shows the main processes within the system. Each of these processes can be broken into further processes until you reach pseudocode.

7. Context Diagram- Registration

8. Level 0 Data Flow Diagram

9. Explosion of Process 4

10. Level 0 – DFD ATM User member banks Printer account database request
Transaction requests
member
banks
ATM
display
Balance
Information
receipt
Printer
Account data
Information
request
account
database

11. A level 1 DFD customer Printer/display Network directory Customer’s
Card details
Rejection
message 1.
Validate
Customer
access 2.
Reject
transaction
\and end session
Access
map
PIN
Access
authorization
Network
directory
customer
Rejection
message 3.
Obtain
Details of
transaction
Access
permissions 4.
Validate
transaction
select
options
Transaction
request

12. A level 2 DFD customer Printer/display Network directory Customer’s
Card details
Cannot
Read
card
1.1
Read
Details
From
card
Printer/display
Card
data
Encoded
pin
1.2
Check
Expiry date
And bank group
customer
1.3
Request
Pin
And match
Max 3 attempts
PIN
Card
Validation data
Access
map
Invalid pin
Access
authorization
Network
directory

13. Another Approach to the ATM Level 1
Get
deposit
Get
inquiry
member
banks
Another Approach to the ATM Level 1
User
bank name
error
account #
error
account #
& deposit
account
display
Validate
deposit
balance
query
& deposit
account #
Make
inquiry
account
database
transaction
Display
data
Validate
inquiry
account #
Printer Do
deposit
transaction
Create
account
summary
account
data