What is a text file?
A text file is a file consisting solely or almost solely of the characters used to make up words, and no other hidden information.
A microsoft word file, for example, although it contains text is not a text file, because as well as text it contains many hidden control characters which specify the fonts, the formatting, the page and paragraph layout and so on.
When you are scanning text, it is important that the file is text only because software can't distinguish between control codes and words without knowing the file format. Storing a file as a text file removes the hidden control characters but retains the textual information, and which is why when a word document is saved as text the formatting is lost.
Ascii and Unicode text files
Text files can be divided into two types - Ascii and Unicode. A Unicode text file can contains text from any different alphabet in the world whereas, an Ascii text file (in the English speaking world) can only contain text written in the Roman alphabet (plus a few accented characters).
A word document can be saved as a Unicode or Ascii text file by using Save As and selecting Unicode (or Ascii) as the file type.
WordFrequencyCounter can analyse text saved as Unicode or Ascii.
Internally, it converts all text to unicode to allow for multi-language support and saves the output as a Unicode text file.