# What is DFD

## What is Data Flow Diagram

DFD stand for data flow diagram. DFD graphically representing the functions, or processes, which capture, manipulate, store, and distribute data between a system and its environment and between components of a system.

A DFD , also known as a "bubble chart" serves the purpose of clarifying system requirements and identifying major transformation that become program in system design . A DFD consists of a series of bubbles joined by lines . the bubbles represent data transformation and lines represent data flows in system . the DFD is a representation of various processes and the input and output in each process . Graphical description of a system's data and how the process transform the data is known as Data Flow Diagram (DFD).

### Why use DFD

Data Flow Diagramming is a means of representing a system at any level of detail with a graphic network of symbols showing data flows, data stores, data processes, and data sources/destination.

### Terms used in DFD

• Process : A process transforms data values The lowest level processes are pure functions without side effects An entire data flow graphics high level process.
• Data flows : A data flow connects the output of an object or process to input of another object or process. It represents the intermediate data value within a computation. It is represented by an arrow and labeled with a description of data, usually its name or type.
• Data store : A data store is a passive object with in a data flow diagram that . stores data for later access.
• External Entity : A rectangle represents an external entity such as a librarian a library member

### Square

A square defines a source (originator) or destination of system data.

### Arrow

An arrow identifies data flow-data in motion. It is a pipeline through which information flows.

### Circle

A circle or a bubble represents is a process that transforms incoming data flow into outgoing data flow. Circle basically represents a process.

### Ractangle

An open Rectangle is data store-data at rest, or temporary repository of data. Open rectangle basically denotes data storage.

### Naming Conventions in DFD

The name of data stores and destination are written in capital latters . process and data flow name have the first letter of each work capitalize.

### Types of DFD

There are two types of DFD Logical DFD and Physical DFD.

Logical DFD

Logical data flow diagram mainly focuses on the system process. It illustrates how data flows in the system. Logical DFD is used in various organizations for the smooth running of system.

Physical DFD

Physical data flow diagram shows how the data flow is actually implemented in the system. Physical DFD is more specific and close to implementation.

Zero Level DFD

One Level DFD