Structured System Analysis and Design: A Free Ebook Guide
Structured system analysis and design is a method of developing information systems that uses graphical tools to model the system components and processes. It is a logical and systematic approach that focuses on the data flow and transformations in a system. Structured system analysis and design can help you understand the current system, identify the user requirements, and design a new system that meets the user needs.
In this ebook, you will learn the basic concepts and techniques of structured system analysis and design, such as:
Data flow diagrams (DFDs) that show the flow of data between processes, data stores, and external entities.
Data dictionary that defines the data elements and their attributes.
Decision trees and decision tables that represent the logic of decision making.
Structured English and pseudocode that describe the steps of a process in a structured way.
Context diagram that gives an overview of the system and its boundaries.
This ebook also provides examples and exercises to help you practice and apply what you learn. You will also find references to other sources of information for further reading.
This ebook is free to download and use for personal or educational purposes. You can access it by clicking on this link[^1^].The following sections will explain each concept and technique of structured system analysis and design in more detail.
Data Flow Diagrams
A data flow diagram (DFD) is a graphical tool that shows the flow of data between processes, data stores, and external entities in a system. A DFD consists of four basic symbols:
A process is represented by a circle or a rounded rectangle. It performs some transformation on the data, such as calculation, validation, sorting, etc.
A data store is represented by an open rectangle. It stores the data for later use, such as a file, a database, or a memory.
An external entity is represented by a square or a rectangle. It is a source or a destination of data outside the system boundary, such as a user, another system, or an organization.
A data flow is represented by an arrow. It shows the direction and the name of the data that flows between the symbols.
A DFD can be drawn at different levels of abstraction, from a high-level overview to a low-level detail. A context diagram is the highest-level DFD that shows the system as a single process and its interactions with external entities. A level 0 DFD is the next level that shows the major processes and data stores within the system. A level 1 DFD is the next level that shows the sub-processes and data flows within each major process. A level 2 DFD is the next level that shows more details of each sub-process.
The following example shows a context diagram and a level 0 DFD for an online bookstore system.
![Context diagram for online bookstore system](#generate_content: an image of a context diagram for online bookstore system)
![Level 0 DFD for online bookstore system](#generate_content: an image of a level 0 DFD for online bookstore system)