How can we discover what programming language a software was written in? For example: Office, Photoshop or any other application and their corresponding languages (C#, Java or ...). Does anyone know?
PEiD offers some info related to the tools used in the development of Windows programs, but is useful only for programmers and other knowledgeable people:
You may look up general info about famous programs like Office individualy by yourself with the help of a search engine or Wikipedia. For example, see the Wikipedia page for Photoshop. Its info table tells us that it has been written in C++.