MATLAB: Converting .001 .002 file

Question

I have a folder of several hundred files with extensions .001 .002 etc How can I rename them such that I retain the detail in the extension but convert them to a more usable file format such as .m file or .txt

So an example of the current filenames:

PUVT0000.000

PUVT0000.001

PUVT0000.002

PUVT0000.003

PUVT0001.002

PUVT0001.004

PUVT0001.005

PUVT0002.004

and what the desired filename:

PUVT0000_000.txt

PUVT0000_001.txt

PUVT0000_002.txt

PUVT0000_003.txt

PUVT0001_002.txt etc.

Answer 1

http://in.mathworks.com/matlabcentral/answers/314319-how-to-rename-a-lot-of-files