This document discusses data flow diagrams (DFDs). It provides background that DFDs were proposed by Larry Constantine in the 1970s and became a popular way to visualize the major steps and data involved in software system processes. A DFD uses graphical representations to show the flow of data through a system using various symbols like processes, data stores, external entities, and data flows. It depicts the end-to-end processing of data through a system by showing the input, process, and output.

2. Data flow diagram were proposed by Larry
Constantine.
In 1970s DFD became a popular way to visualize
the major steps and data involved in Software System
Processes.

3. It is a graphical representation of data flow.
It shows the processing steps as data flows through
the system.
It shows end to end processing of data.
It takes input - process – output view of the system.
It plays important roll while developing the project.

4. DATA FLOW: it shows movement of data flows
origin to destination
PROCESS: People , Procedures or devices that
use data.
Entity: source of data or Destination of data
which may be people , program interact with
the system but are outside its boundary.
Data Store: Information that is kept and
accessed. May be in paper file folder or a
database . It may be exploded into various
levels namely level 0 ,level 1 , level 3 etc.

5. Payroll
Processing
System
Departments
Human
Resources
Govt.
Agencies
Employees
Bank
Manage-
ment
Employee checks

6. 1.0
Update
Empl.
Payroll
File
2.0
Pay
Employ-
ees
5.0
Update
Gen.
Ledger
4.0
Pay
Taxes
3.0
Prepare
Reports
Employee/
Payroll File
General
Ledger
Human
Resources
Depart-
ments Employees
Bank
Govt.
Agencies
Manage-
ment
Employee
change
form
New employee
form
Time
cards
Employee
paychecks
Payroll
check
Payroll
disburse-
ment data
Payroll tax
disb. voucher
Tax report
& payment
Payroll
report

7. A minimum of one data flow in and
one data flow out of a process
A data store must be connected to a
process(either in, out, or both)
An external entity must be connected
to a process (either in, out, or both)
A single data flow must only flow one
way

8. Process has no data flowing into it, but has
data flowing out.
Data store is hooked to external entity.
This means external entity can read and
write to your data file without auditing!!
The data flow goes in two directions at
once. Two or more arrows should be used
to show the flow to and from each
process.

9. They shows the flow of data through the system.
It shows process of i/o data.
It is also called as Bubble chart.
DFD supports a top – down approach for analysis

10. A state is a mode or condition of being.
A state diagram is a dynamic model showing
changes of state that an object goes through during
its lifetime in response to events.
State diagram depict the dynamic behavior of the
system in response to external and internal events.

11. Initial state : It is a starting point or first activity of diagram. This is
also known as “pseudo state” where the state has no variables and no
activity.
Final state : It is the end of the state diagram. This is also a pseudo
state because it does not have any variables or action described. A state
diagram can have zero or more final states.
State : state is a recognizable situation and exists over an interval of
time. This is denoted by a rounded rectangle and compartments within
to describe state-name, variable and activity.
or
State-name
Variable
Activity

12. Transition : A transition is a change from one state to other is indicated
by an arrow. The event and action causing the transition are written
beside the arrow, separated by a slash.
Event and Action: A trigger that causes a transition to occur and changes
the state is called as an event or action. An event occurs at a particular
time has no duration.
Signal : when an event causes a message/trigger to be sent to a state,
that causes the transitions; then, that message sent by the event is
called as a signal. This is represented as <<Signal>> icon above the
action/event.
Event [condition]/Action
<<signal>>
Event/ Action
Event /Action

13. Enter Admin
Login
Invalid ID or
Password
<<Main menu page>>
Do: uploading , editing
personal details , sending
messages etc.
<<Check>>
Do: Admin Login
Try again
YesNo
User want to Stop
Valid ID and
Password
Selecting
activities <<upload file>>
Do: choose file
<<Personal info>>
Do: change password ,
change E-mail id , change
details etc.
<<send msg>>
Do: sending message
If
select
editing
person
al
detail
If select
sending
messages
If select uploading
User want to Cancel
User want to Cancel
User want to Cancel
Waiting
for
upload
file

14. State chart diagram is used to represent the event driven state
change of a system. It basically describes the state change of a class,
interface etc.
State chart diagram is used to visualize the reaction of a system
by internal/external factors.
State diagram (also called state chart diagrams) are used to help
the developer better understand any complex functionality of
specialized areas of the system.