They can be easier to spell by saying the silent letter—g" h" ost.
说出那个无声的字母可以让这些字更容易拼出来－－g" h" ost(鬼魂)。
英语百科
Personal Storage Table
In computing, a Personal Storage Table (.pst) is an open proprietary file format used to store copies of messages, calendar events, and other items within Microsoft software such as Microsoft Exchange Client, Windows Messaging, and Microsoft Outlook. The open format is controlled by Microsoft who provide free specifications and free irrevocable technology licensing.