What is COCOMO? Explain COCOMO model in detail.

The Constructive Cost Model (COCOMO) is the most widely used software estimation model in the world. It was developed by Barry Boehm of TRW and first published in his book Software Engineering Economics in 1981. The COCOMO model predicts the effort and duration of a project based on inputs relating to the size of the resulting systems and a number of "cost drives" that affect productivity. The most fundamental calculation in the COCOMO model is the use of the Effort Equation (Equation1) to estimate the number of Person-Months required developing a project. Most of the other COCOMO results, including the estimates for Requirements and Maintenance, are derived from this quantity.

COCOMO is defined in terms of three different models:

·        The Basic Model

·        The Intermediate Model

·        The Detailed Model

The Basic Model:

Basic COCOMO model estimates the software development effort using only a single predictor variable (size in DSI) and three software development modes. Basic COCOMO is good for quick, early, rough order of magnitude estimates of software costs, but its accuracy is necessarily limited because of its lack of factors which have a significant influence on software costs. The Basic COCOMO estimates are within a factor of 1.3 only 29% of the time, and within a factor of 2 only 60% of the time.
The Basic COCOMO Model estimate for annual software maintenance is calculated in terms of Annual Change Traffic (ACT). ACT is the fraction of the software product's source instructions which undergo change during a (typical) year, either through addition or modification.

The Intermediate Model:

The Intermediate model use an Effort Adjustment Factor (EAF) and slightly different coefficients for the effort equations than the Basic model. You can apply Intermediate COCOMO across the entire software product for easily and roughly cost estimation during the early stage, or apply it at the software product component level for more accurate cost estimation in more detailed stages.