The document discusses the design phase of the system development life cycle. It explains that the design phase involves planning how the software specifications will be implemented. Key aspects of design discussed include structured analysis and design, data flow diagrams, synchronous and asynchronous operations, and design characteristics like correctness, understandability, efficiency and maintainability. The document also covers important design concepts like modularity, abstraction, coupling and cohesion which help to partition problems and create independent, understandable and maintainable modules. It provides examples to illustrate concepts like hierarchical decomposition, fan-in and fan-out, and different types of coupling and cohesion.

1. Guide:
Er. Deepinder Kaur
Presented By:
Sonali
Nikhil
Pallavi

3. Computer software, or
just software, is a
collection of computer
programs and related
data that provides the
instructions for
telling a computer
what to do and how to
do it.
Software is a set of
programs, procedures,
algorithms and its
documentation
concerned with the
operation of a data
processing system.

4. System Development Life Cycle

5. We are going to
study about the
design phase.

6. Design elements describe the desired
software features in detail
These design elements are intended to
describe the software in sufficient detail.
The focus of this process is to cover the gap
between understanding the specification and
implementing them in the software
Design process takes inputs of software
specifications and is dedicated to plan for
implementation of the software.

7. Design Phase
Structured Structured
Analysis design

8. Structured analysis
 Structured Analysis (SA) in
software engineering and its
allied technique, Structured
Design (SD), are methods for
analyzing and converting
business requirements into
specifications and ultimately,
computer programs, hardware
configurations and related
manual procedures.

9. Scenario based
Behavioral Analysis model
Flow oriented based
Class based

10. To describe customer
requirement
To establish basis of
design

11.  A data flow diagram (DFD)
is a graphical representation of
the "flow" of data through an
information system, modeling
its process aspects.
 A DFD shows what kinds of
information will be input to and
output from the system, where
the data will come from and go
to, and where the data will be
stored.

12. Synchronous Asynchronous
operations operations
If data goes to a
If data is going from 1
data store then to
bubble to another
other bubble

13. Level 0 P
0 Balancing
DFD’s
P1
Level 1
0.1
P11 P12
Level 2 0.1.1 0.1.2

14.  Also known as “high – level design”
 Software architecture is made with the help of
structured charts

15. Characteristics of Software Design
Correctness
Understandability
Efficiency
Maintainability

16. Process Outcome
Identify nature of Requirement
requirement. specification
Analysis & build Functional
modal specification
system
Mismatch b/w
Validate solution modal & design
are removed
Refine design solution Design blueprint
Implement design Software
solution architecture

17. cohesion
abstraction coupling
Concepts Problem
modularity partitioning
of design & hierarchy

18. Modularity
Concept of keeping
separate the various
unrevealed aspects
A
of a system so that
each aspect can be
studied in isolation. B C

19. It helps in system debugging.
In system repairs.
In system building.

20. Condition must for
modularity!!
Each module needs
to support a well-
defined abstraction &
have a clear interface
through which it can
interact with other
modules.

21. Decomposition
Is creating lower level elements from higher lever key element
on the basis of functions & features.
Result of this is called MODULES.

22.  Abstraction of a component describes the
external behaviour of that component without
bothering with the internal details that produce
the behaviour
 It is essential for problem partitioning.

23. Functional Data
abstraction abstraction

24. • Is the basis of partitioning in the functional oriented
approach
1.
• when problem is being partitioned ,the complete
transformation function for the system is partitioned into
2. smaller functions
• The decomposition of the system is in terms of functional
modules
3.

25.  It supports certain operations required
from a data object, depending on the
object & environment in which it is used.
 Only such operations are visible &
internals are hidden.
 It forms the basis of object oriented
design.

26. Rule of “Divide & Conquer”.
Goal is to divide the problem into manageable small pieces that can be solved
separately
The cost of solving the entire problem is more than the sum of the cost of
solving all the pieces
Different pieces have to cooperate & communicate to solve larger problem
The design produced by using problem partitioning can be represented as a
hierarchy of components

27. Hierarchical structure makes it much easier to comprehend larger problems
All design methodologies aim to produce a design that employs hierarchical
structures

28.  Fan-in refers to no. of units that use
a particular software unit.
 Fan-out refers to no. of units used by
particular software unit

29. Fan-in for B
is 1 & fan- Super-ordinate
of B & C
out is 2
A
Sub-ordinate of A
& super-ordinate of
D,E&F B C
Sub-ordinate of B
&C D E F

30.  Two modules are considered independent if one can
function completely without the presence of other.
 The more connections between the modules ,the more they
are dependent.
 Hence, fewer & simpler the connections between modules
the easier is to understand them.

31.  Coupling is the strength of A B
interconnections between
Highly
modules. coupled
 Highly – coupled modules
D C
are joined by strong
interconnections. A B
 While loosely-coupled
Loosely
modules have weak
connections. D C
 Independent modules have
no interconnections. A Uncoupled B

32.  Coupling increases the complexity.
 To minimize coupling , the no. of interfaces per module.
 Interface is used to pass information to & from modules.

33. Reference made from 1 module to another
Amount of data passed from 1 module to another
Amount of control passed from 1 module to another

34.  It represents how tightly bound the internal elements
of the module are to 1 another.
 It gives an idea whether the different elements of a
module belong together in the same module.
 Greater the cohesion of each module in the system ,
lower the coupling between modules is.

35. Co-incidental
logical
temporal
procedural
communicational
sequential
functional

37. Component level design
Interface design
Architectural design
Data/class design

38.  Known as structural decomposition: actually a
conversion of Data flow Diagram to Structured
chart

39.  Selection: determined by “diamond”. This means condition will
checked & depending on these modules will be executed.
Process
Process Process

40.  Using “semi-circular arrow we represent this.
 This arrow includes a link to a module implying
that module is executed multiple times
A
B C D

41. Module A
Invocation
arrow
Parameters

42. Input module: obtain info. From subordinate &
passes to super-ordinate
Input
module

43. Output module : takes info. From their
super-ordinate & pass to sub-ordinate.
Output module

44. Transform module : that
transform data into other form.
Transform module

45. Co-ordinate module: manages info. To & from other
sub-ordinates.
Co-ordinate module
A B

46. Composite module: perform function of more than 1
module.
Composite module
B C

47. Transformation of DFD to structured
design.
Identify system
Identify input Identify output
processing
transform transform
transform

48. Main
A,n
sum
A,n
a
A,n
readnums Sort Add_n
X,y X,y
switch

49. Any questions

50. Thankyou you
Made By :
Sonali Narang
B.Ca