Dwords .txt is created in the same folder as is your program EXE file placed. KILL is the same as DEL under DOS, delete all file types, not just text files.
Again. In program begin is all contens from Dwords.txt loaded to array Words. Then, if is NOT new record add to array Words, is nothing saved and Dwords.txt file is the same as in begin. If is some new word added to array Words, are all records from array Words writed to file Dwords2.txt Then is old file Dwords.txt deleted and Dwords2.txt renamed as Dwords.txt