COCOMO I is a software cost estimation model published in 1981 by Barry Boehm. It uses a waterfall lifecycle approach and estimates development effort as a function of program size (measured in KDSI) and 15 cost drivers. The model has three levels - basic, intermediate, and detailed - with the detailed version incorporating impacts on each development phase. While transparent, it is difficult to accurately estimate size early on and vulnerable to misclassifying development mode. Success relies on tuning the model using organizational historical data.

1. Software Project Management
Presentation Topic:
COCOMO I
Presented by: Syed Mutahir Pirzada

2.  COCOMO stands for Constructive Cost Model
 "constructive" implies that the complexity
 First published by Dr. Barry Boehm in 1981
 Two models being used. . .
 A. COCOMO I
 B. COCOMO II

4.  Also called COCOMO'81
 Underlying S/W life cycle is waterfall life cycle
 Boehm proposed three levels of the model: 1.
Basic
2. Intermediate
3. Detailed

5.  A single-valued, static model
 Computes software development effort (and-
cost) as a function of program size
 Expressed in estimated thousand delivered -
source instructions (KDSI)

6.  It computes software development effort as a
function of program
 Size and a set of fifteen "cost drivers" that
include subjective assessments of product,
hardware,
 Personnel, and project attributes.

7.  It incorporates all characteristics of the
intermediate version
 With an assessment of the cost driver’s impact
on each step (analysis, design, etc.) of the
software engineering process

8. ADVANTAGES OF
COCOMO'81

9.  COCOMO is transparent
 One can see how it works unlike other models
such as SLIM(Software lifecycle management)
 Drivers are particularly helpful to the estimator
to understand the impact of different factors
that affect project costs

10. DISADVANTAGES OF
COCOMO'81

11.  It is hard to accurately estimate KDSI early on in
the project, when most effort estimates are
required
 KDSI,(number of thousand delivered source
instructions) actually, is not a size measure it is a
length measure
 Extremely vulnerable to misclassification of the
development mode
 Success depends largely on tuning the model to
the needs of the organization, using historical data
which is not always available