介绍简单三层架构的PPT

表现层（UI）：通俗讲就是展现给用户的界面，即用户在使用一个系统的时候他的所见所得。

２、业务逻辑层（BLL）：用于根据业务 逻辑向表现层提供 数据。

３、数据访问层（DAL）：该层所做事务直接操作数据库，针对数据的增添、删除、修改、更新、查找等

-PPT introduced a simple three-tier presentation layer (UI): popular talk show to the user interface is that users in the use of a system when seen from him. 2, the business logic layer (BLL): According to the business logic for providing data to the presentation layer. 3, the data access layer (DAL): The transaction done directly with the database layer for the data to add, delete, modify, update, search, etc.