I needed to prefix a long list of files with a number, so I looked around and did not find much info, so I thought it might be useful for someone if I post it here (yes, some of us are still using Windows).
Here is how to prefix files:
for %i in (*.*) do (ren "%i" "prefix %i")
And here is how to prefix folders:
for /D %i in (*.*) do (ren "%i" "prefix %i")
For syntax is explained on Microsoft’s web site: For in batch files.