1. Shashwat Shriparv
dwivedishashwat@gmail.com
InfinitySoft

3.  Estimating the cost of a Software product is
one of the most difficult and error prone tasks.
 Cost estimates can be of two types:
1) Top down approach
2) Bottom up approach

4. TOP DOWN APPROACH
♣ It focuses on system level cost like computing
resources as well as the cost of configuration
management ,quality assurance ,system integration
,training and publications.
♣ It focuses on system level cost but may overlook
various technical factors.

5. BOTTOM UP APPROACH
♣ It first estimates the cost to develop each module
and these cost are combined to arrive at an overall
estimate.
♣ It emphasizes the cost associated with developing
individual system components but fail to account
for system level costs.

6. METHODS FOR ESTIMATION
1) Expert Judgment
2) Delphi Cost Estimation
3) Work Breakdown Structures
4) Algorithmic Cost Models

8.  Compute the estimate cost of the software system
as the sum of costs of the modules and the
subsystem that comprises the system.
 They follow Bottom Up Approach.

9. CONSTRUCTIVE COST MODEL

10. ☺ This is one of the most widely used and discussed
software cost estimation in the industry.
☺ It has evolved into a more comprehensive
estimation model called COCOMO II.
☺In the COCOMO model Effort Multipliers are
used to adjust the estimate for product attribute
,computer attribute ,personal attribute and project
attribute.

11. ☺ The following activities are covered by the
estimates:
a) Covers estimate through acceptance
testing
b) Includes the cost of documentation and
reviews.
c) Includes the cost of Project Manager.

12. ☺ The cost estimators exclude planning and
analysis costs ,installation and training cost and
cost of computer operators , secretaries.
☺ The DSI (Delivered Source Instruction) estimate
includes job control statement and source
statements but excludes comments
☺ It is considered to be one line or card image.

13. Following are the assumptions estimated by the
COCOMO concerning the nature of the software:-
1) Careful definition and validation of requirements
is performed by a small number of capable people.
2) Requirements remain stable throughout the
project
3) Careful definition and validation of architectural
designs is performed by a small number of capable
people.

14. 4) Detailed design ,coding and unit testing are
performed in parallel by group of programmers
working in teams.
5) Integration Testing is based on early test
planning.
6) Interface errors are found by unit testing and by
inspections.

15. Formally there are mainly 10 steps to estimate
the cost using COCOMO:-
1) Identify all the subsystem and modules in the
product.
2) Estimate the size of each module and calculate the
size of each subsystem and the total system.

16. 3) Specify the module level multipliers.
4) Compute the module effort and the time
estimates for each modules.
5) Specify the effort multipliers for each
subsystems.
6) From Steps 4 and 5 compute the estimated
effort and development time for each subsystems.

17. 7) From Step 6 compute the total system effort
and development time.
8) Perform sensitivity analysis on the estimate.
9) Add other development cost like planning and
analysis that are not included in the estimates.
10) Compare this estimate with the one developed
by Delphi estimation .Identify and Rectify the
differences in the estimates.

18. MODULE LEVEL MULTIPLIERS
Product Complexity
Programmers Capability
Virtual Machine Experience
Programming Language Experience

19. EFFORT MULTIPLIERS
PERSONAL ATTRIBUTES
• Analyst capability
•Programmer capability
•Application experience
• Virtual machine experience
• Programming language experience
 PROJECT ATTRIBUTES
• Use of modern programming practices
• Use of software tools
• Required schedule

20. PRODUCT ATTRIBUTES
Required Reliability
Data-base Size
Product Complexity
COMPUTER ATTRIBUTES
Execution time constraint
Main storage Constraint
Virtual machine reality
Computer turnaround time

21. ADVANTAGES:-
o The model can be used to gain insight into the cost
factors.
o Systematic techniques of software engineering are
used throughout the development process.
o Data can be collected and analyzed ,new factors
can be identified and effort multipliers can be
adjusted.

22. Shashwat Shriparv
dwivedishashwat@gmail.com
InfinitySoft