Constructive Cost Model     [B. Boehm]

Hierarchy of COCOMO models (parameters)

basic:  prg size

intermediate:  prg size & cost drivers

advanced: prg size & cost drivers per phase

Cost Drivers: Team Capability, Product Complexity, Reliability, Problem Domain Experience, Development practices, Tools, Language Experience, etc.


  • number and complexity of functions
  • number and complexity of modules
  • number of lines of code
  • number and duration of steps in your development process
  • skills and technologies involved

Basic Relation

  • person-month / nbr-of-people = duration
  • example:

–36 person-month, 1 developer, 36 month

–36 person-month, 2 people, 18 month

–36 person-month, 12 people, 3 month

Project Types

organic mode:

–relatively small and simple

–small team of skilled developers

small size, little innovation, relax deadline, stable environment


–intermediate in size and complexity

–mixed skill levels on the team

Medium size, Medium innovation, Medium deadline, Medium environment


–hard constraints for HW, SW, operation

large size, Greater innovation, Tight deadline, Complex environment like hardware and interface

COCOMO 2 models

  • Application composition model. Used when software is composed from existing parts.
  • Early design model. Used when requirements are available but design has not yet started.
  • Reuse model. Used to compute the effort of integrating reusable components.
  • Post-architecture model. Used once the system architecture has been designed and more information about the system is available.


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