Can I easily combine several txt files into one?

pu1. We can open each file, copy and paste it over and over again

2017-12-25

OK

pu2. 1. Open one file to select all
2. ctrl+c
3. Open a new txt file and ctrl+v
4. Open another file to select all
5. ctrl+c
6. Ctrl+v in the new txt file that I opened earlier
7. Repeat and repeat

2017-12-25

OK

pu3. There's a simple way to do it on Linux, but not on Windows

2017-12-25

OK