Thread: Design question

I have to make an application and I have a doubt about its design. In the application it will be very important the performance. The application has a console input interface and a core which make calculations.

I have now two options:

1) Create a new thread to do calculations and so the application will have two of them: one for input/output management and other for doing the staff.

2) Only one thread which do all, and do periodic reads to the input console.

My doubt is about the 1). will it be more costly to the performance of the appl.? (....as it is a resource managed by s.o.) which of both is better...?

Not really familiar with threads, but if there's to be any output back to the console interface, there's no sense in having two threads as the output will be waiting for the calculations to finish.

It depends. How much I/O are you doing? If it is just a user interactive program WHO CARES? If you are being fed bunches of data and you have to spit that data out as quickly as possible, maybe go with two (or three) threads: one to get data, one to process data, and one to output data. If you are expected to quickly process lots of data, you'll need to buffer each layer.