---
title: "Short note: COCOMO"
subject: "Software Engineering"
chapter: 8
key: "semester_5/software_engineering:cocomo-note"
source: https://www.bctengineer.com/q/semester_5/software_engineering/cocomo-note
site: BCT Engineering
---

# Short note: COCOMO

Software Engineering · Chapter 8: Software Testing and cost Estimation

- Asked in: 2068 Chaitra, 2.5 marks
- Video: [What is COCOMO Model? | Software Engineering](https://www.youtube.com/watch?v=OJEzV8cqJUI) — Learn Coding
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/software_engineering/cocomo-note
- Whole chapter: https://www.bctengineer.com/md/semester_5/software_engineering/chapter-8

## Question

Write a short note on COCOMO.

## Short answer

COCOMO by Barry Boehm is an algorithmic cost model: Effort E = a × (KLOC)^b PM, time D = c × E^d months. Modes: organic (a=2.4, b=1.05), semi-detached (3.0,1.12), embedded (3.6,1.20) with c=2.5, d=0.38/0.35/0.32. Levels: basic, intermediate (15 cost drivers), detailed. COCOMO II adds scale factors and function points.

## Answer

**COCOMO (Constructive Cost Model)** is an algorithmic model by Barry Boehm (1981) that estimates software **effort** and **schedule** from the estimated size in KLOC.

**Basic equations**
- Effort E = a × (KLOC)^b person-months
- Development time D = c × (E)^d months
- Staff = E / D; Productivity = KLOC / E

**Modes**

| Mode | Project type | a | b | c | d |
|---|---|---|---|---|---|
| Organic | Small, familiar, simple | 2.4 | 1.05 | 2.5 | 0.38 |
| Semi-detached | Medium, mixed experience | 3.0 | 1.12 | 2.5 | 0.35 |
| Embedded | Tight constraints | 3.6 | 1.20 | 2.5 | 0.32 |

**Levels:** basic (size only), intermediate (15 cost drivers form an effort adjustment factor) and detailed (cost drivers per phase).

**Example:** a 32 KLOC organic project needs E = 2.4 × 32^1.05 ≈ 91 PM and D = 2.5 × 91^0.38 ≈ 13.9 months.

**COCOMO II** updates the model with scale factors, effort multipliers and size measures such as object points and function points. COCOMO is simple and well documented, but its accuracy depends on a good size estimate and on calibration to the organisation's own data.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What does basic COCOMO estimate from size in KLOC?
   A. Only the number of defects
   B. Effort in person-months and development time
   C. Only the testing cost
   D. Only the hardware needed
   Answer: B. COCOMO (Boehm, 1981) estimates effort and schedule from the estimated size. (Key point: What COCOMO estimates)

2. Which mode has the tightest constraints and the largest exponent (b = 1.20)?
   A. Organic
   B. Semi-detached
   C. Embedded
   D. Intermediate
   Answer: C. Embedded projects have tight hardware/operational constraints, with a = 3.6 and b = 1.20. (Key point: Modes of COCOMO)

3. What does intermediate COCOMO add to basic COCOMO?
   A. Cost drivers forming an effort adjustment factor
   B. Function points only
   C. A fixed team size
   D. Object points
   Answer: A. Intermediate COCOMO uses 15 cost drivers to adjust effort; detailed applies them per phase. (Key point: COCOMO levels)