CherryTree - A hierarchical note taking application, featuring rich text and syntax highlighting, storing data in a single xml or sqlite file.
Notepad++ - A free source code editor which supports several programming languages running under the MS Windows environment.
Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.
Snappify - snappify is a great tool to create and adjust beautiful code snippets easily.
Standard Notes - A safe place for your notes, thoughts, and life's work
Boostnote - Boostnote is an open-source note-taking app.