The Constructive Cost Model (COCOMO) is a software cost estimation model that helps

predict the effort, cost, and schedule required for a software development project. Developed by
Barry Boehm in 1981, COCOMO uses a mathematical formula based on the size of the
software project, typically measured in lines of code (LOC).

Table of Content
 What is the COCOMO Model?
 Types of Projects in the COCOMO Model
 Detailed Structure of COCOMO Model
 Importance of the COCOMO Model
 Types of COCOMO Model
 CASE Studies and Examples
 Advantages of the COCOMO Model
 Disadvantages of the COCOMO Model
 Best Practices for Using COCOMO
 Important Questions on COCOMO Model
 Conclusion
 Frequently Asked Questions on COCOMO Model -FAQs

What is the COCOMO Model?

The COCOMO Model is a procedural cost estimate model for software projects and is often
used as a process of reliably predicting the various parameters associated with making a project
such as size, effort, cost, time, and quality. It was proposed by Barry Boehm in 1981 and is
based on the study of 63 projects, which makes it one of the best-documented models.

The key parameters that define the quality of any software product, which are also an
outcome of COCOMO, are primarily effort and schedule:

1. Effort: Amount of labor that will be required to complete a task. It is measured in

person-months units.

2. Schedule: This simply means the amount of time required for the completion of the
job, which is, of course, proportional to the effort put in. It is measured in the units of time such
as weeks, and months.

Types of Projects in the COCOMO Model

 In the COCOMO model, software projects are categorized into three types based on their
complexity, size, and the development environment. These types are:

1. Organic: A software project is said to be an organic type if the team size required is
adequately small, the problem is well understood and has been solved in the past and also the
team members have a nominal experience regarding the problem.

2. Semi-detached: A software project is said to be a Semi-detached type if the vital

characteristics such as team size, experience, and knowledge of the various programming
environments lie in between organic and embedded. The projects classified as Semi-Detached
are comparatively less familiar and difficult to develop compared to the organic ones and
require more experience better guidance and creativity. Eg: Compilers or different Embedded
Systems can be considered Semi-Detached types.

3. Embedded: A software project requiring the highest level of complexity, creativity,

and experience requirement falls under this category. Such software requires a larger team size
than the other two models and also the developers need to be sufficiently experienced and
creative to develop such complex models.

Comparison of these three types of Projects in COCOMO Model

Aspects Organic Semidetached Embedded

Project Size 2 to 50 KLOC 50-300 KLOC 300 and above KLOC
Complexity Low Medium High

Team Some experienced as well Mixed experience, includes

Highly experienced
Experience as inexperienced staff experts

Somewhat flexible, Highly rigorous, strict

Environment Flexible, fewer constraints
moderate constraints requirements
Effort
E = 2.4(400)1.05 E = 3.0(400)1.12 E = 3.6(400)1.20
Equation
New system interfacing
Example Simple payroll system Flight control software
with existing systems

Detailed Structure of COCOMO Model

 Detailed COCOMO incorporates all characteristics of the intermediate version with an
assessment of the cost driver’s impact on each step of the software engineering process. The
detailed model uses different effort multipliers for each cost driver attribute. In detailed
COCOMO, the whole software is divided into different modules and then we apply COCOMO
in different modules to estimate effort and then sum the effort.

The Six phases of detailed COCOMO are:

Phases of COCOMO Model

1. Planning and requirements: This initial phase involves defining the scope,
objectives, and constraints of the project. It includes developing a project plan that outlines the
schedule, resources, and milestones

2. System design: : In this phase, the high-level architecture of the software system is
created. This includes defining the system’s overall structure, including major components,
their interactions, and the data flow between them.

3. Detailed design: This phase involves creating detailed specifications for each
component of the system. It breaks down the system design into detailed descriptions of each
module, including data structures, algorithms, and interfaces.
 4. Module code and test: This involves writing the actual source code for each module
or component as defined in the detailed design. It includes coding the functionalities,
implementing algorithms, and developing interfaces.

5. Integration and test: This phase involves combining individual modules into a
complete system and ensuring that they work together as intended.

6. Cost Constructive model: The Constructive Cost Model (COCOMO) is a widely

used method for estimating the cost and effort required for software development projects.

Different models of COCOMO have been proposed to predict the cost estimation at different
levels, based on the amount of accuracy and correctness required. All of these models can be
applied to a variety of projects, whose characteristics determine the value of the constant to be
used in subsequent calculations. These characteristics of different system types are mentioned
below. Boehm’s definition of organic, semidetached, and embedded systems:

Importance of the COCOMO Model

1. Cost Estimation: To help with resource planning and project budgeting, COCOMO
offers a methodical approach to software development cost estimation.

2. Resource Management: By taking team experience, project size, and complexity into
account, the model helps with efficient resource allocation.

3. Project Planning: COCOMO assists in developing practical project plans that include
attainable objectives, due dates, and benchmarks.

4. Risk management: Early in the development process, COCOMO assists in identifying

and mitigating potential hazards by including risk elements.

5. Support for Decisions: During project planning, the model provides a quantitative
foundation for choices about scope, priorities, and resource allocation.

6. Benchmarking: To compare and assess various software development projects to

industry standards, COCOMO offers a benchmark.

7. Resource Optimization: The model helps to maximize the use of resources, which
raises productivity and lowers costs.

Types of COCOMO Model

 There are three types of COCOMO Model:

 Basic COCOMO Model

 Intermediate COCOMO Model

 Detailed COCOMO Model

1. Basic COCOMO Model

The Basic COCOMO model is a straightforward way to estimate the effort needed for a
software development project. It uses a simple mathematical formula to predict how many
person-months of work are required based on the size of the project, measured in thousands of
lines of code (KLOC).

It estimates effort and time required for development using the following expression:

E = a*(KLOC)b PM

Tdev = c*(E)d

Person required = Effort/ Time

Where,

E is effort applied in Person-Months

KLOC is the estimated size of the software product indicate in Kilo Lines of Code

Tdev is the development time in months

a, b, c are constants determined by the category of software project given in below table.

The above formula is used for the cost estimation of the basic COCOMO model and also is
used in the subsequent models. The constant values a, b, c, and d for the Basic Model for the
different categories of the software projects are:

Software Projects a b c d
Organic 2.4 1.05 2.5 0.38
Semi-Detached 3.0 1.12 2.5 0.35
Embedded 3.6 1.20 2.5 0.32
 1. The effort is measured in Person-Months and as evident from the formula is dependent
on Kilo-Lines of code. The development time is measured in months.

2. These formulas are used as such in the Basic Model calculations, as not much
consideration of different factors such as reliability, and expertise is taken into account,
henceforth the estimate is rough.

Example of Basic COCOMO Model

Suppose that a Basic project was estimated to be 400 KLOC (kilo lines of code). Calculate
effort and time for each of the three modes of development. All the constants value provided in
the following table:

Solution

From the above table we take the value of constant a,b,c and d.

1. For organic mode,

o effort = 2.4 × (400)1.05 ≈ 1295 person-month.

o dev. time = 2.5 × (1295)0.38 ≈ 38 months.

2. For semi-detach mode,

o effort = 3 × (400)1.12 ≈ 2462 person-month.

o dev. time = 2.5 × (2462)0.35 ≈ 38 months.

3. For Embedded mode,

o effort = 3.6 × (400)1.20 ≈ 4772 person-month.

o dev. time = 2.5 × (4772)0.32 ≈ 38 months.