DIEM has been designed to protect your privacy as much as possible.
DIEM requires a one-off connection to the internet, in order to download the setup program. After that, DIEM does everything locally, on your pc, and never contacts the internet.
By default, DIEM is installed into a subfolder of your Program Files folder. Thereafter, DIEM never attempts to write to the installation folder.
DIEM does write to a few files, however. These files are stored in a subfolder of your "My Documents" folder, called Diem Solutions\1.0. First DIEM maintains a file which contains the data you have inputted so far. Second, the program allows you to configure some settings, and they are stored in a small file here so that DIEM can remember them for next time. Lastly, if you save any of the graphs as an image, the image will be saved as a file in this folder. The file is named using the current time, and given the appropriate extension. It is perfectly possible to go into this folder and open these files independently of DIEM: the configuration file is just a text file, and the data file is a SQLite database. If you edit or delete these files, you do so at your own risk, and DIEM might not work properly afterwards.