offsets

I think I'm going about this the wrong way, or rather perhaps there is a better way.

Should I load the entirety of the file into the appropriate data structures in one go and then have my "print to screen" parts tap into what is in them, or should I do it piecewise as needed where the function to print out one kind of data seeks to the location in the file where that data lives and then gets it?

EDIT:

Problem #1 right now is that the file I have been reading is really old and doesn't even have all the various data types - just spike waveforms. I'll have to remember to make a small file for myself at work tomorrow.