How to save digital output from ARDUINO UNO to .csv or txt file on my computer?

I would like to have my Arduino UNO tell to my computer through the Serial port whenever one of those inputs changes state, then all the data will save in .csv file or test file.

Use a serious terminal program like RealTerm. That can log all serial communications into a file.

If you need extra information like the time when the message arrived then you either need the Arduino to put that into the serial data stream or you need to write your own program (in a language such as Processing or Python) and do that work on the PC side.

Don't be spooked by the above.

If you need extra information like the time when the message arrived

then you simply set RealTerm to add the timestamp to the data being received. It does this by using the PC clock. There is no need for Arduino to put anything into the data stream, and you don't have to know anything about Python or Processing.

Also note the discussion hereabouts on PLX v2, which feeds your data directly into Excel. Again, no need to mess about getting the time, that's a job for Excel. Indeed, if you have Excel, and Arduino is always connected to PC by USB cable while operating, PLX is a better choice than a terminal. You can even have live graphs.