[Coder-san]

Open an exe in Notepad (or NotePad++), then search for bottom text:

msvbvm60.dll (or similar) = VB6 Application
Microsoft.VisualStudio.Editors (or similar) = .NET Application
(None of these and dll names at almost the EOF) = C/C++ Application

However, packers and obfuscators are there for a reason. They will make it difficult to find out.

Look for OllyDebug, it decompiles executables in Assembler language.