COCOMO model in Software Engineering - Step-by-Step Execution

Concept Flow - COCOMO model

Start: Project Size Estimation

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Select COCOMO Model Type

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Basic

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Calculate Effort

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Calculate Development Time

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Estimate People Required

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Project Plan

The COCOMO model starts by estimating project size, choosing a model type, then calculating effort, time, and staffing to plan the project.

Execution Sample

Software Engineering

Effort = a * (Size)^b
Time = c * (Effort)^d
People = Effort / Time

Calculates effort, development time, and people needed based on project size using COCOMO formulas.

Analysis Table

Step	Variable	Calculation	Value	Explanation
1	Size	Given	100 KLOC	Project size in thousands of lines of code
2	Model Type	Selected	Basic	Simple COCOMO model chosen
3	Effort	2.4 * (100)^1.05	302.1 Person-Months	Effort estimated using formula for Basic model
4	Time	2.5 * (302.1)^0.38	21.9 Months	Development time estimated
5	People	302.1 / 21.9	13.8 People	Average staff needed
6	End	-	-	Estimation complete

💡 All calculations done; project effort, time, and staffing estimated.

State Tracker

Variable	Start	After Step 3	After Step 4	After Step 5	Final
Size (KLOC)	100	100	100	100	100
Effort (Person-Months)	N/A	302.1	302.1	302.1	302.1
Time (Months)	N/A	N/A	21.9	21.9	21.9
People (Count)	N/A	N/A	N/A	13.8	13.8

Key Insights - 3 Insights

Why does the effort increase more than linearly with project size?

Because the effort formula uses an exponent greater than 1 (1.05), effort grows faster than size, reflecting complexity increase (see Step 3 in execution_table).

Why do we divide effort by time to get people?

People needed is effort spread over time, so dividing total person-months by months gives average staff (Step 5).

What changes if we select Intermediate or Detailed model?

They add adjustment factors for project attributes, changing coefficients and calculations beyond the basic formula (not shown in this simple trace).

Visual Quiz - 3 Questions

Look at the execution_table at Step 3, what is the effort calculated for 100 KLOC?

A 100 Person-Months

B 302.1 Person-Months

C 16.7 Person-Months

D 2.4 Person-Months

💡 Hint

Check the 'Value' column at Step 3 in execution_table.

At which step does the model estimate the number of people needed?

A Step 5

B Step 4

C Step 2

D Step 6

💡 Hint

Look for the step where People is calculated in execution_table.

If the project size doubles, how does the effort change according to the formula?

A Effort doubles exactly

B Effort increases less than double

C Effort increases more than double

D Effort stays the same

💡 Hint

Refer to the exponent 1.05 in the effort formula in execution_sample.

Concept Snapshot

COCOMO Model Quick Reference:
- Input: Project size (KLOC)
- Effort = a * (Size)^b (a,b depend on model type)
- Time = c * (Effort)^d
- People = Effort / Time
- Models: Basic, Intermediate, Detailed
- Estimates effort, time, and staffing for software projects

Full Transcript

The COCOMO model helps estimate software project effort, time, and staffing based on project size. First, you estimate the size in thousands of lines of code (KLOC). Then, you select a model type: Basic, Intermediate, or Detailed. Using formulas with coefficients and exponents, you calculate the effort in person-months, the development time in months, and the average number of people needed. For example, with 100 KLOC and the Basic model, effort is about 302 person-months, time about 22 months, and staff about 14 people. Effort grows faster than size due to complexity. Dividing effort by time gives staffing. More detailed models adjust calculations with project attributes. This step-by-step process helps plan software projects realistically.