If you read through the recipe, Selecting columns from the output in Passing Data through the Pipeline, you may skip this recipe. This recipe has been created in the interest of context as well as those who have skipped the said chapter/recipe.

Calculated properties is another form of performing calculations on the fly. Here is the scenario:

You need a report of all the files present in a certain directory, with the names of the files, the last modified date, the full paths and the sizes in MB.