---
title: "Cohesion and coupling in software"
subject: "Instrumentation II"
chapter: 9
key: "semester_5/instrumentation_ii:cohesion-coupling"
source: https://www.bctengineer.com/q/semester_5/instrumentation_ii/cohesion-coupling
site: BCT Engineering
---

# Cohesion and coupling in software

Instrumentation II · Chapter 9: Software For Instrumentation And Control Applications

- Asked in: 2076 Chaitra, 3 marks
- Video: [Cohesion and Coupling in Software Engineering](https://www.youtube.com/watch?v=NweTzHYBgYU) — Gate Smashers
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/instrumentation_ii/cohesion-coupling
- Whole chapter: https://www.bctengineer.com/md/semester_5/instrumentation_ii/chapter-9

## Question

Describe cohesion and coupling.

## Short answer

Cohesion measures how closely elements within a module are related; high cohesion (functional) is desirable. Coupling measures interdependence between modules; low coupling (data coupling) is desired. Good design aims for high cohesion and low coupling to enhance maintainability and reusability.

## Answer

#### Cohesion
**Cohesion** is the degree to which the elements inside a single module belong together and perform one well-defined task. High cohesion is desirable, as the module is easy to understand, test and reuse. Levels (low to high): coincidental, logical, temporal, procedural, communicational, sequential, functional (best). Example: a function that only calculates the CRC has functional cohesion; a "utility" function doing unrelated jobs has coincidental cohesion.

#### Coupling
**Coupling** is the degree of interdependence between different modules. Low coupling is desirable: a change in one module does not affect others, which makes maintenance and testing simpler. Types (high to low): content, common (global data), control, stamp, and data coupling (best, only needed parameters are passed).

Good design aims for **high cohesion and low coupling**, which gives modular, maintainable and reusable software.

## Check yourself

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

1. Desirable cohesion?
   A. Low cohesion
   B. High cohesion
   C. Coincidental
   D. Logical
   Answer: B. Module performs one well-defined task. (Key point: Cohesion)

2. Desirable coupling?
   A. Content coupling
   B. High coupling
   C. Low coupling
   D. Common coupling
   Answer: C. Changes don't affect others. (Key point: Coupling)

3. Best coupling type?
   A. Content coupling
   B. Common coupling
   C. Control coupling
   D. Data coupling
   Answer: D. Only needed parameters are passed. (Key point: Best types)

4. Example of functional cohesion?
   A. A function that only calculates a CRC
   B. A utility doing unrelated jobs
   C. A function mixing I/O and math
   D. A catch-all function
   Answer: A. One task means functional cohesion. (Key point: Functional cohesion)

## Related in other subjects

- [Short note: cohesion and coupling](https://www.bctengineer.com/question.md?key=semester_5%2Fsoftware_engineering%3Acohesion-coupling) — Software Engineering, chapter 3