Before this option is selected, it must be the case that (1) data records have been created in the Data worksheet, and (2) control lines, or "cards", have been placed in the CCs worksheet.
The way the Interpret option works depends on a setting in row 7 of Lertap's System worksheet where the "user run mode" is controlled.
By far the most common setting is "normal mode". The discussion below, in the rest of this topic, assumes that this is the setting. A following topic discusses the "Elmillon direct" user run mode.
When Lertap's "user run mode" is set to the normal mode, then, the first time the Interpret option is clicked on, Lertap gets Excel to read the responses found in the Data worksheet, looking in the columns specified in the *col lines of the CCs worksheet.
If there are no errors in the CCs worksheet, Lertap and Excel will produce new worksheets. One of them is called "Freqs", for frequencies.
It is possible to get Lertap to automatically roll through from "Interpret CCs lines" to "Elmillon item analysis" without stopping, as detailed in the following topic: Production mode.
If the "Interpret CCs lines" is later selected again, a warning message will appear, saying that there's a possibility of losing data. This is purely precautionary -- Lertap is about to delete Freqs, Scores, Stats1f, and so forth -- but this is usually only natural; new versions of these same worksheets will be generated, which is almost always what users want. (Lertap is being overly cautious in sounding this warning; the primary worksheets, Data and CCs, are never affected by this action. Nor are any other special user-created worksheets, such as, perhaps, the coding guide seen in this example.)
For a related topic, see "deleting secondary worksheets".
Chapter 9 in the printed manual also discusses these matters.