---
title: "Short note: structured design"
subject: "Information System"
chapter: 5
key: "semester_8/information_system:short-note-structured-design"
source: https://www.bctengineer.com/q/semester_8/information_system/short-note-structured-design
site: BCT Engineering
---

# Short note: structured design

Information System · Chapter 5: Planning for IS

- Asked in: 2069 Bhadra (old course), 4 marks
- Video: [08 - System Analysis and Design | What is structured analysis | What is structured design](https://www.youtube.com/watch?v=YM_mrcvQbFA) — Touseef Jamal
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_8/information_system/short-note-structured-design
- Whole chapter: https://www.bctengineer.com/md/semester_8/information_system/chapter-5

## Question

Write a short note on Structured design.

## Short answer

Structured design uses top‑down decomposition to create a hierarchy of independent modules with high cohesion and low coupling. It converts data flow diagrams into structure charts showing module calls and data flow, making systems easier to understand, test, and maintain, though it separates data from processes.

## Answer

**Structured design** is a design methodology that breaks a system into a hierarchy of small, independent modules, using top-down decomposition. It follows structured analysis (data flow diagrams) and converts it into a modular program structure.

#### Key ideas
- **Top-down decomposition:** start with the whole system and refine it into sub-functions until each module does one task.
- **Modularity:** each module has a single, well-defined function.
- **High cohesion:** elements inside a module are closely related.
- **Low coupling:** modules depend on each other as little as possible and communicate by simple parameters.
- **Hierarchical control:** a boss module calls subordinate modules.

#### Tools
- **Data flow diagram (DFD):** input to design.
- **Structure chart:** shows modules, the calling hierarchy and data passed between them.
- **Data dictionary and pseudo-code/decision tables** for module logic.

```text
        [Main Program]
        /     |      \
  [Input] [Process] [Output]
            /   \
        [Calc] [Validate]
```

#### Advantages
Easy to understand, test and maintain; modules can be reused; work can be divided among team members; errors are easy to locate.
#### Limitation
Separates data from processes, so it is less suitable for very large or changing systems than object-oriented design.

## Check yourself

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

1. Good structured design aims for:
   A. Low cohesion and high coupling
   B. High cohesion and low coupling
   C. High cohesion and high coupling
   D. Low cohesion and low coupling
   Answer: B. Module elements should be closely related (high cohesion), with minimal dependence between modules (low coupling). (Key point: Cohesion and coupling)

2. What does a structure chart show?
   A. Modules, the calling hierarchy and data passed between them
   B. Database tables only
   C. Hardware wiring
   D. User passwords
   Answer: A. A structure chart shows modules, hierarchy and parameters passed. (Key point: Structure chart)

3. How does structured design decompose a system?
   A. Bottom-up with no hierarchy
   B. Top-down, refining into sub-functions until each module does one task
   C. Randomly
   D. By objects only
   Answer: B. It starts with the whole system and refines it top-down. (Key point: Approach)

## Related in other subjects

- [Encapsulation and abstraction working together](https://www.bctengineer.com/question.md?key=semester_6%2Fobject_oriented_analysis_and_design%3Aencapsulation-abstraction-together) — Object Oriented Analysis and Design, chapter 1