TextSTAT is described as 'simple programme for the analysis of texts. It reads plain text files (in different encodings) and HTML files (directly from the internet) and it produces word frequency lists and concordances from these files'. There are three alternatives to TextSTAT for Windows, Linux and Mac. The best alternative is Yoshikoder, which is free. Other great apps like TextSTAT are Antconc (Free) and WordSmith Tools (Paid).
AntConc is a freeware, multiplatform tool for carrying out corpus linguistics research and data-driven learning. It runs on any computer running Microsoft Windows (tested on Win 98/Me/2000/NT, XP, Vista, Win 7)