By default, in windows, show extensions is set to disabled.
This means that your textfile will have the name: text
but in reality this is text.txt
.
If you rename text to text.for, or in the save as form, you wrote text.for, in reality this is named as text.for.txt
In a save as dialog, there is always the option to choose the save as type. If you select Show all files (*.*)
and you then enter text.for, it will actually save as text.for.
Alternatively, you can enable showing extensions, and it does not matter if you specify the save as type anymore.
To show extensions, open your explorer window and go to the options.
Go to the tab View
and from the list, find [v] Hide extensions for known filetypes
and uncheck it.