Course Name: Software

Project Management
Course Code: CSET324
Program: B.Tech. (Vth SEM)

By- Dr Ambrish Kumar

Assistant Professor
SCSET Bennett University, Greater Noida
Email Address: Ambrish.kumar@bennett.edu.in
The Constructive Cost Model (COCOMO)
Constructive Cost model
(COCOMO)

Basic Intermediate Detailed

Model proposed by
B. W. Boehm’s
through his book
Software Engineering Economics in 1981
2
 COCOMO applied to

Semidetached
Organic mode Embedded
mode mode

3
 Mode Project size Nature of Project Innovation Deadline of Development
the project Environment

Organic Typically Small size project, experienced Little Not tight Familiar & In
developers in the familiar house
2-50 KLOC
environment. For example, pay
roll, inventory projects etc.

Semi Typically Medium size project, Medium Medium Medium Medium

detached size team, Average previous
50-300 KLOC
experience on similar project.
For example: Utility systems
like compilers, database
systems, editors etc.

Embedded Typically over Large project, Real time Significant Tight Complex
systems, Complex interfaces, Hardware/
300 KLOC customer
Very little previous experience.
For example: ATMs, Air Traffic Interfaces
Control etc. required

Table 4: The comparison of three COCOMO modes

4
Basic Model

Basic COCOMO model takes the form

E = ab (KLOC) bb

D = cb (E) db

where E is effort applied in Person-Months, and D is the development time in

months. The coefficients ab, bb, cb and db are given in table 4 (a).

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 Software ab bb cb db
Project

Organic 2.4 1.05 2.5 0.38

Semidetached 3.0 1.12 2.5 0.35

Embedded 3.6 1.20 2.5 0.32

Table 4(a): Basic COCOMO coefficients

6
When effort and development time are known, the average staff size to complete
the project may be calculated as:

E
Average staff size (SS) = Persons
D

When project size is known, the productivity level may be calculated as:

KLOC
Productivity (P) = KLOC / PM
E

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Example: 4.5

Suppose that a project was estimated to be 400 KLOC.

Calculate the effort and development time for each of the
three modes i.e., organic, semidetached and embedded.

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Solution

The basic COCOMO equation take the form:

E = ab (KLOC) bb
D = cb (KLOC) d b
Estimated size of the project = 400 KLOC

(i) Organic mode

E = 2.4(400)1.05 = 1295.31 PM
D = 2.5(1295.31)0.38 = 38.07 PM

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(ii) Semidetached mode

E = 3.0(400)1.12 = 2462.79 PM
D = 2.5(2462.79)0.35 = 38.45 PM

(iii) Embedded mode

E = 3.6(400)1.20 = 4772.81 PM
D = 2.5(4772.8)0.32 = 38 PM

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Example: 4.6

A project size of 200 KLOC is to be developed. Software development team has

average experience on similar type of projects. The project schedule is not very
tight. Calculate the effort, development time, average staff size and productivity of
the project.

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Solution

The semi-detached mode is the most appropriate mode; keeping in view the size,
schedule and experience of the development team.

Hence E = 3.0(200)1.12 = 1133.12 PM

D = 2.5(1133.12)0.35 = 29.3 PM

E
Average staff size (SS) = Persons
D

1133.12
= = 38.67Persons
29.3
12
 KLOC 200
Productivity = = = 0.1765 KLOC / PM
E 1133.12

P = 176 LOC / PM

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Intermediate Model
Cost drivers
(i) Product Attributes
➢ Required s/w reliability

➢ Size of application database

➢ Complexity of the product

(ii) Hardware Attributes

➢ Run time performance constraints

➢ Memory constraints

➢ Virtual machine volatility

➢ Turnaround time
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(iii) Personal Attributes
➢ Analyst capability

➢ Programmer capability

➢ Application experience

➢ Virtual m/c experience

➢ Programming language experience

(iv) Project Attributes

➢ Modern programming practices

➢ Use of software tools

➢ Required development Schedule

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 Multipliers of different cost drivers

Cost Drivers RATINGS

Very low Low Nominal High Very Extra
high high
Product Attributes

RELY 0.75 0.88 1.00 1.15 1.40 --

DATA -- 0.94 1.00 1.08 1.16 --

CPLX 0.70 0.85 1.00 1.15 1.30 1.65

Computer Attributes

TIME -- -- 1.00 1.11 1.30 1.66

STOR -- -- 1.00 1.06 1.21 1.56

VIRT -- 0.87 1.00 1.15 1.30 --

TURN -- 0.87 1.00 1.07 1.15 --

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 Cost Drivers RATINGS
Very low Low Nominal High Very Extra
high high
Personnel Attributes

ACAP 1.00 0.86 0.71 --

1.46 1.19
AEXP --
1.29 1.13 1.00 0.91 0.82
PCAP 0.86 0.70 --
1.42 1.17 1.00
VEXP -- --
1.21 1.10 1.00 0.90
LEXP 1.14 1.07 1.00 0.95 -- --
Project Attributes

MODP --
1.24 1.10 1.00 0.91 0.82
TOOL 1.24 1.10 1.00 0.91 0.83 --
SCED
1.23 1.08 1.00 1.04 1.10 --

Table 5: Multiplier values for effort calculations

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Intermediate COCOMO equations

E = ai (KLOC) bi * EAF
D = ci (E) di

Project ai bi ci di

Organic 3.2 1.05 2.5 0.38

Semidetached 3.0 1.12 2.5 0.35

Embedded 2.8 1.20 2.5 0.32

Table 6: Coefficients for intermediate COCOMO

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Detailed COCOMO Model
Detailed COCOMO

Phase-Sensitive Three level

effort multipliers product hierarchy

Cost Modules
driver design subsystem
System level
s & test
Manpower allocation for
each phase
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Development Phase
Plan / Requirements
EFFORT : 6% to 8%
DEVELOPMENT TIME : 10% to 40%
% depend on mode & size

Effort = a * (Size)^b * EAF * Mode Factors

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Design
Effort : 16% to 18%
Time : 19% to 38%

Programming
Effort : 48% to 68%
Time : 24% to 64%

Integration & Test

Effort : 16% to 34%

Time : 18% to 34%

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Principle of the effort estimate
Size equivalent

As the software might be partly developed from software already existing (that is,
re-usable code), a full development is not always required. In such cases, the parts
of design document (DD%), code (C%) and integration (I%) to be modified are
estimated. Then, an adjustment factor, A, is calculated by means of the following
equation.

A = 0.4 DD + 0.3 C + 0.3 I

The size equivalent is obtained by

S (equivalent) = (S x A) / 100

Ep =  p E
Dp =  p D
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Lifecycle Phase Values of p
Mode & Code Plan & System Detailed Module Integration
Size Requirements Design Design Code & Test & Test

Organic Small
0.06 0.16 0.26 0.42 0.16
S≈2
Organic
0.06 0.16 0.24 0.38 0.22
medium S≈32
Semidetached
0.07 0.17 0.25 0.33 0.25
medium S≈32
Semidetached
0.07 0.17 0.24 0.31 0.28
large S≈128
Embedded
0.08 0.18 0.25 0.26 0.31
large S≈128
Embedded
extra large 0.08 0.18 0.24 0.24 0.34
S≈320

Table 7 : Effort and schedule fractions occurring in each phase of the

lifecycle 23
Lifecycle Phase Values of p
Mode & Code Plan & System Detailed Module Code Integration
Size Requirements Design Design & Test & Test

Organic Small
0.10 0.19 0.24 0.39 0.18
S≈2
Organic
0.12 0.19 0.21 0.34 0.26
medium S≈32
Semidetached
0.20 0.26 0.21 0.27 0.26
medium S≈32
Semidetached
0.22 0.27 0.19 0.25 0.29
large S≈128
Embedded
0.36 0.36 0.18 0.18 0.28
large S≈128
Embedded
extra large 0.40 0.38 0.16 0.16 0.30
S≈320

Table 7 : Effort and schedule fractions occurring in each phase of the

lifecycle 24