This dialog lists all the character encodings supported by your computer. The encoding that is currently being used by the active file is initially selected. Select the encoding that you wish to use from the list, then click OK.
Converting a file from one character encoding to another
When opened with the Set encoding 
ribbon command, this window enables you to change the code page that is being used to encode the file in the active file panel. The file on disk will not be affected until you save the file.
The code page that is currently being used is prefixed with an asterisk (*). You can select any other code page (or Unicode option) from the list. When you have chosen a different code page, click OK and Merge will then translate the file from its current code page into the new code page.
When translating from one code page to another, there may be characters that have no translated equivalent in the target code page. These characters are converted into question mark (?) characters. For the majority of common translations, this will rarely be an issue. For translations between radically different code pages (for example, from Japanese to English), there may be a large number of characters that cannot be translated.
Reopening a file with a different code page
If you open a file using the incorrect code page, some (or all) characters may not appear correctly. In this case, you can use the Reopen with encoding… command in the file panel’s context menu (right-click) to reopen the file with the correct code page. The command will display this window so that you can choose a different code page to use. Other files displayed within the file comparison window are not affected, and will continue to use the code pages with which they were opened.
Languages
Select this option if you want to use a language’s ANSI code page. The contents of the adjacent list will change to show code pages ordered by language and country.
Code pages
Select this option if you want to choose a specific code page number to use. The contents of the adjacent list will change to show code pages ordered by code page number.