继续学习第三章创建项目。

1. Double-click Diagram2 to open the corresponding Diagram editor.

双击图表2，打开相应的编辑器

2. The Diagram editor is divided into three panes: the declaration pane, the code pane, and the message pane. (See Figure 14).

图表编辑器分成三个面板：声明面板，代码面板和消息面板（见图14）

Figure 14. The editor for Diagram2

图14. 图表2的编辑器

3. Select the Variables tab, and place the cursor in the upper left-hand cell in the declaration pane and type Photo_Cell.

选择变量选项卡，把光标放在声明面板左上角单元格，输入Photo_Cell。

4. Move one cell to the right by pressing the tab key. Type bool in the “Data type” column. Move the cursor to next column labeled “Attributes”.

按下tab键向右移动一个单元格。在数据类型列输入bool。移动光标倒下一个标签为Attributes的单元格。

5. Choose the default setting retain (which means that the variable will keep its value at a warm restart). Press the tab key to move to the next column.

选择默认的设置（这意味着该变量在热启动时保持数值）。按下tab键移动到下一列。

6. Set the initial value to false to indicate that the doors are closed at start-up.

设置初始值为false，表明开始时们是关闭的。

7. Skip the column I/O address. The address will be automatically filled in later when connecting variables to I/O channels.

忽略IO列地址。后续链接变量到IO通道时，地址将自动填充。

8. The last column ‘Description’ is reserved for you to use freely. Your first row should now look like row 1 in Figure 15.

最后一列描述保留供你自由使用。你的第一行现在看起来像图15第一行的样子。

Figure 15. Declaration of the Boolean variable Photo_Cell

图 15. 声明布尔型变量Photo_Cell

9. Declare a second variable named, DoorsOpen_Time which represents how long (duration time) the doors should remain open. Complete the declaration of DoorsOpen_Time according to row 2 in Figure 16.

声明第二个名字叫做DoorsOpen_Time的变量，代表门保持打开的时间长度（持续时间）。按照图16第二行完成DoorsOpen_Time的声明。

Figure 16. Declaration of the DoorsOpen_Time variable

图 16. 声明DoorsOpen_Time变量

Note the attribute constant of the variable DoorsOpen_Time. You can either explicitly type “constant”, or scroll through the available formats using Alt-key together with the up and down arrow keys, or press CTRL+J to display the list of attributes and then select constant.

注意 DoorsOpen_Time变量的属性常量。可以显式键入“常量”，也可以使用 Alt 键和向上和向下箭头键滚动浏览可用格式，或者按 Ctrl+J 显示属性列表，然后选择常量。

10. Declare the next variable DoorsOpen_ET using a different method. Right click the code pane (grid area), and select New > Variable. In the New Variable dialog, declare the values for the variable as shown in Figure 17 and click OK.

使用一个不同的方法声明下一个变量DoorsOpen_ET。右键电机代码面板（网格区域），选择新建> 变量。在新建变量对话框，按照图17声明各数值，点击OK按钮。

Figure 17. New Variable dialog

图 17. 新建变量对话框

The new variable, DoorsOpen_ET, gets inserted as a graphical object in the code pane. It also appears in the Declaration Pane as row 3.

新的变量DoorsOpen_ET，作为图形对象插入代码面板。它同时出现在声明面板第三行。

Figure 18. Declaration of the DoorsOpen_ET variable

图 18. 声明DoorsOpen_ET变量

11. Declare the remaining variables using any of the two methods (starting from row 4 to row 10) in the grid according to Figure 19.

按照图19在表格中使用两种方法之一声明剩余的变量（从第4行到第10行）

Figure 19. Declaration of the remaining variables

图 19. 声明剩余的变量

12. Select the Communication Variables tab in the Diagram editor, and declare the Service_Req communication variable as shown in Figure 20.

在图表编辑器选择通讯变量选项卡，如图20所示声明Service_Req通讯变量。

Figure 20. Declaration of the communication variable Service_Req

图 20. 声明通讯变量Service_Req

13. Click Check  to check for errors

点击检查图标检查错误

14. Click Save  to save the variables

点击保存图标保存变量