To maintain the data to be displayed by the tableview, we need to maintain a DataSource object that implements the UITableViewDataSource protocol. The datasource object manages the tableview data. The datasource object performs the following main tasks.
* It reports the number of rows and sections to be displayed in the tableview.
* It allocates the reusable cells for each row in the tableview.
* It provides the titles for headers and footers in the tableview sections.
