Alarms within DCS

Hello friends,

I am working on a project at the moment where I am calculating how many IO are required. I have been inputting all of the alarms in this schedule as if they are a actual input. But then it hit me, I am not sure whether these are just set points within the DCS and this is all done via software, programmed via the DCS site engineer after being told of their set points.

I am far from an expert in this field, and I wonder if anyone can tell me a bit more about whether these class as new IO or not?

I have seen them on instrument indexes before, for example... a PT with a L and H alarm could have a list of components such as : - PT, PI, PIAL, PIAH.

But I am getting confused as to what would count as an instrument and go on the index, and what would be an actual I/O.

Any help is greatly appreciate,