Layered, new third board layered

Layered, new third board layered

1. UI (user layer), BLL (business logic layer), DAL (data access layer ).
The UI is used for display, such as some display styles and interface design.

BLL is used to handle business logic problems.

DAL deals with databases. 

2. Data Access Layer: This Layer is at the bottom Layer and is responsible for interacting with the database, also known as the Data Access Layer (DAL ).

Presentation Layer: This Layer directly deals with users and is responsible for displaying or retrieving data, also known as the User Interface Layer ). Whether using the console or Windows Forms to display data, it is an application of the presentation layer.

The presentation layer depends on the data access layer. The two layers of functions are separated to assist in the work and their dependencies.

3. Advantages and features of hierarchical development:

(1) code reuse

(2) separated developers' concerns

(3) lossless replacement

4. in a three-tier architecture, the so-called three-tier development refers to dividing the entire business application into the presentation layer-business logic layer-data access layer-database and so on. Some of them need to be more detailed, clearly dividing the presentation layer, business logic access, and data access and database access of the client is very conducive to system development, maintenance, deployment and expansion.