# Input tab

The **Input** tab allows you to specify how fields from the incoming stream of the Simple Mapping (sub-transformation) step are mapped to the fields of the Mapping Input Specification in the sub-transformation.

![Input tab in Simple Mapping (sub-transformation)](/files/pphZYntpZmrquihQyegt)

| Option                                  | Description                                                                                                                                                                                                                                                     |
| --------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Fieldname from source step**          | Specify the name of a field in the incoming stream.                                                                                                                                                                                                             |
| **Fieldname to mapping input step**     | Specify the name of the field as it will be known to the sub-transformation.                                                                                                                                                                                    |
| **Mapping**                             | Use this button to open a field mapping dialog box. This will conveniently list all the available fields in both the parent transformation and the sub-transformation, and allow you to create field to field mappings.                                         |
| **Update mapped fieldnames downstream** | Select this option to rename fields back to their original names when they reach the Mapping output step (fields get renamed before they are transferred to the mapping transformation). This will make your sub-transformations more transparent and reusable. |

To add inputs into the table, perform the following steps:

1. Click the **Mapping** button.
2. Click a **Source Field** you want to map.
3. Click a **Target Field** to associate with the **Source Field**.
4. Click **Add**. If you need to edit or change the **Source Field** or **Target Field**, click **Delete**.
5. Click **Ok**.


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