The intermediate COCOMO model recognizes this fact and refines the initial estimate obtained using the basic COCOMO expressions by using a set of 15 cost drivers (multipliers) based on various attributes of software development.

Therefore, in order to obtain an accurate estimation of the effort and project duration, the effect of all relevant parameters must be taken into account.

However, a host of other project parameters besides the product size affect the effort required to develop the product as well as the development time.

The basic COCOMO model assumes that effort and development time are functions of the product size alone.

But, if anyone completes the project over a longer period of time than the estimated, then there is almost no decrease in the estimated cost value.

if anyone tries to complete the project in a time shorter than the estimated duration, then the cost will increase drastically.

Effort and the duration estimations obtained using the COCOMO model are called as nominal effort estimate and nominal duration estimate.

It is the area under the person-month plot as shown in fig.

The effort estimation is expressed in units of person-months (PM).

Effort is the total effort required to develop the software product, expressed in person months (PMs).

Tdev is the estimated time to develop the software, expressed in months,.

a1, a2, b1, b2 are constants for each category of software products,.

KLOC is the estimated size of the software product expressed in Kilo Lines of Code,.

The basic COCOMO estimation model is given by the following expressions.

The basic COCOMO model gives an approximate estimate of the project parameters.

According to Boehm, software cost estimation should be done through three stages:.

According to Boehm, software cost estimation should be done through three stages: Basic COCOMO, Intermediate COCOMO, and Complete COCOMO.

Embedded: A development project is considered to be of embedded type, if the software being developed is strongly coupled to complex hardware.

Semidetached: A development project can be considered of semidetached type, if the development consists of a mixture of experienced and inexperienced staff.

Organic: A development project can be considered of organic type, if the project deals with developing a well understood application program, the size of the development team is small, and the team members are experienced in developing similar types of projects.

According to the Boehm any software development project can be classified into one of the following three categories based on the development complexity: organic, semidetached, and embedded.

COCOMO (Constructive Cost Estimation Model) was proposed by Boehm (1981).

Cocomo model types