The document discusses the process of system design, which goes through logical and physical design phases. Logical design involves data flow diagrams and defining user needs, while physical design specifies design details for programmers. Structured design uses tools like data flow diagrams, data dictionaries, and structure charts to decompose the system into modules. A key part of design is structured walkthroughs where peers review and provide feedback on the design. User involvement is also important throughout the design process.

1. Process of
Design
By:-Bharat Razdan
Diksha Goel
Bsc IT (IV)

2. PROCESS OF DESIGN
 The design phase focuses on the
detailed implementations of the
system recommended in the feasibility
study.
 The design phase is a transition from
a user-oriented document to a
document oriented to the
programmers or data base personnel.

3. System design goes through two
phases of development
 Logical Design
 Physical Design

4. Logical Design
 A data flow diagrams shows the logical flow
of system and defines the boundaries of the
system.
 For a candidate system it describes the
inputs(source), outputs(destination), data
bases(data stores), and procedures(data
flow) all in a format that meet the users
requirements.
 When analysts prepare the logical system
design they specify the user needs at a level
of detail that virtually determines the
information flow into and out of the system
and the required data resources.

5. Physical Design
 This produces the working system by
defining the design specifications that tell
programmers exactly what the candidate
system must do.
 In turn , the programmer writes the
necessary programs or modifies the
software package that accepts input from
the user, performs the necessary
calculations through the existing or data
base , produces the report on the hard
copy or display it on the screen and
maintains an updated data base at all
times.

6. Contd..
 Physical system design consists of the
following steps:
◦ Design the physical system.
 Specify input/output media.
 Design the database and specify backup
procedures.
◦ Plan system implementation.
◦ Devise a test and implementation plan and
specify any new hardware /software.
◦ Update benefits, costs , conversion date ,
and system constraints(legal , financial ,
hardware , etc).

7. Structured Design
 Structured design is a data-flow-based
methodology . The approach begins with
a system specifications that identifies
inputs and outputs and describes the
functional aspects of the system.
 From the DFD, the next step is the
definition of the modules and their
relationships to one another in a form
called a structure chart, using a data
dictionary and other structured tools.

8. The Structured Design
Method
Structured
English
System Data Decision
Specifications DFD Dictionary tree
Decision
table

9.  Structured design is an attempt to
minimize complexity and make a
problem manageable by subdividing it
into smaller segments, which is called
modularization or decomposition.
 A design is said to be top-down if it
consists of a hierarchy of modules,
with each module having a single
entry and a single exit subroutine.

10. The advantage of this design are
as follows:-
◦ Critical interfaces are tested first.
◦ Early versions of the design, though
incomplete, are useful enough to
resemble the real system.
◦ Structuring the design , provides control
and improves morale.
◦ The procedural characteristics define the
order that determines processing.

11. Functional Decomposition
 It is a graphic tool for representing
hierarchy .
 It has three elements:-
 The module is represented by a
rectangle with a name. It is a contiguous
set of statements.
 The connection is represented by a
vector linking two modules. It usually
means one module has called another
module.
 The couple is represented by an arrow
with a circular tail. It represents data
items moved from one module to
another.

12. Module
A
The module is represented with a name.
A
B C
The connection is represented by a vector linking two modules.
It usually means one module has called another module

13. Coupling
A
B C
The couple is represented by an arrow with a circular tale.
It represents data items moved from one module to another .
In the figure O,P,Q are couples . Module A calls B passing O
downward
Like wise module A calls C, passing P downward and receiving Q
back.

14. Structured Walkthrough
 Structured walkthrough is an
interchange of ideas among peers
who review a product presented by its
authors .
 The purpose is to anticipate as many
problems in the design as possible.
 It is cheaper to make changes now
than later during conversation. This is
a practical implementation of “ A stitch
in time saves nine”

15. User Involvement
 Walkthroughs may be held at various
points in the system development life
cycle.
 They are held to review the system test
plan, program design, and production
acceptance.
 Promoting a user‟s contribution in the
walkthrough and throughout the design
phase can be crucial for successful
implementation.
 It also bridges the gap between the
designer, who as a staff person has an
expert perspective , and the user with a
generalist or managerial view.

16. QUIZ
Q)How do we design physical system?
a) Specify I/P, O/P media-> design database-> design
physical information flow-> design physical design
walkthrough
b) design database-> Specify I/P, O/P media-> design
physical information flow-> design physical design
walkthrough
c) design database-> design physical information flow->
design physical design walkthrough -> Specify I/P, O/P
media
d) design physical information flow-> design physical design
walkthrough -> Specify I/P, O/P media-> design database

17. Q)System specifications‟ are formulated
in which designing phase?
a) Physical design
b) Logical design
c) Structure design
d) None of the above

18. Q)„Procedure specifications‟ are
formulated in which designing
phase?
a) Logical design
b) Structure design
c) Physical design
d) Feasibility design

19. Q)What is the purpose of structured
design?
a) To increase reproducibility.
b) To increase repeatability.
c) For documentation purpose.
d) To minimize complexity of problem.

20. Q)What is not a development activity in
structured design?
a) Database design
b) Implementation planning
c) User documentation
d) Feasibility study

21. Q) The process of interchanging ideas
among peers when reviewing a
product is known as
a) Coupling
b) Structured Walkthrough
c) Logical Design
d) Physical Design