Structure Chart represents the hierarchical structure of modules. It breaks down the entire system into the lowest functional modules and describes the functions and sub-functions of each module of a system in greater detail. This article focuses on discussing Structure Charts in detail.
What is a Structure Chart?
Structure Chart partitions the system into black boxes (functionality of the system is known to the users, but inner details are unknown).
- Inputs are given to the black boxes and appropriate outputs are generated.
- Modules at the top level are called modules at low level.
- Components are read from top to bottom and left to right.
- When a module calls another, it views the called module as a black box, passing the required parameters and receiving results.
Symbols in Structured Chart
1. Module
It represents the process or task of the system. It is of three types:
- Control Module: A control module branches to more than one submodule.
- Sub Module: Sub Module is a module which is the part (Child) of another module.
- Library Module: Library Module are reusable and invokable from any module.
2. Conditional Call
It represents that control module can select any of the sub module on the basis of some condition.
3. Loop (Repetitive call of module)
It represents the repetitive execution of module by the sub module. A curved arrow represents a loop in the module.
4. Data Flow
It represents the flow of data between the modules. It is represented by a directed arrow with an empty circle at the end.
5. Control Flow
It represents the flow of control between the modules. It is represented by a directed arrow with a filled circle at the end.
6. Physical Storage
It is that where all the information are to be stored.
Example
Structure chart for an Email server
Types of Structure Chart
- Transform Centered Structure: These type of structure chart are designed for the systems that receives an input which is transformed by a sequence of operations being carried out by one module.
- Transaction Centered Structure: These structure describes a system that processes a number of different types of transaction.