SciTE is a powerful programmer's editor and Notepad replacement based on the popular open-source Scintilla (a component used within many other editing tools).
You don't need to be a developer to use the program. It looks much like Notepad, so at a minimum you can just launch it, type some text and save the file, using all the keyboard shortcuts you know already.
It won't take long to notice small benefits. Pressing Ctrl+N creates a new tab, for instance, allowing multiple documents to be open at once. And Ctrl+F gives you a persistent search area at the bottom of the screen, where you can instantly mark all search hits as well as zip through them one-by-one.
Start exploring the program and you'll quickly discover more. Regular expression searches, find across files, drag and drop editing (select some lines, drag and drop them somewhere else), case conversion, bookmarking, session management.
There's also plenty of developer-oriented power, including syntax highlighting, brace handling, code folding, and options to compile and run programs, turning it more into a basic IDE.
Version 3.7.5 Changelog
Released 26 May 2017.
Support dropped for Microsoft Visual C++ 2013 due to increased use of C++11 features.
Added a caret line frame as an alternative visual for highlighting the caret line.
Added "Reverse Selected Lines" feature.
SciTE adds "Select All Bookmarks" command.
SciTE adds a save.path.suggestion setting to suggest a file name when saving an unnamed buffer.
Updated case conversion and character categories to Unicode 9.
The Baan lexer recognizes numeric literals in a more compliant manner including hexadecimal numbers and exponentials.
The Bash lexer recognizes strings in lists in more cases. Bug #1944.
The Fortran lexer recognizes a preprocessor line after a line continuation &. Bug #1935.
The Fortran folder can fold comments. Bug #1936.
The PowerShell lexer recognizes escaped quotes in strings. Bug #1929.
The Python lexer recognizes identifiers more accurately when they include non-ASCII characters.
The Python folder treats comments at the end of the file as separate from the preceding structure.
The YAML lexer recognizes comments in more situations and styles a "..." line like a "---" line. Bug #1931.
Update scroll bar when annotations added, removed, or visibility changed. Feature #1187.
Canceling modes with the Esc key preserves a rectangular selection. Bug #1940.
Builds are made with a sorted list of lexers to be more reproducible. Bug #1946.
On Cocoa, a leak of mouse tracking areas was fixed.
On Cocoa, the autocompletion is 4 pixels wider to avoid text truncation.
On Windows, stop drawing a focus rectangle on the autocompletion list and raise the default list length to 9 items.
SciTE examines at most 1 MB of a file to automatically determine indentation for indent.auto to avoid a lengthy pause when loading very large files.
SciTE user interface uses lighter colours and fewer 3D elements to match current desktop environments.
SciTE sets buffer dirty and shows message when file deleted if load.on.activate on.
SciTE on Windows Find strip Find button works in incremental no-close mode. Bug #1926.
SciTE isn't the most powerful of programmer's editors, but it's also easier to use than many, and the core editor (Scintilla) is one of the best around. If you're not currently happy with some other Notepad replacement, it's a must-try.