Is there any program for writing pieces of code offline?

Question

Web development

Ideally, you want codepen , gist or jsfidle offline
so that you can open 1 note and look at the necessary code, which can consist of html + css + js + php
without a program, it looks something like

папкаНазваниеКусочкаКода/
    js.txt
    html.txt
    css.txt
    php.txt

but you must admit it would be convenient to see all the code at once and copy if necessary