Hi.
I'm a rusty old hardware design engineer who's written stuff in fortran, basic and assembler since the late 1970's then used VB6 and C.

Now I'm trying to do basic engineering type tasks in this new fandangled 'Processing' language as I'm so impressed by what I've seen it doing in data visualisations and so forth. (And I'm using arduinos so it seems fitting).

(....and I dont have visual studio any more)    

So, the first thing I need to do is to spool data from a serial port to a disk file on the PC for later analysis.
Reading serial ports looks straight forward enough, but what I need to understand is how to append binary data a byte (or a few bytes) at a time to a disk file. (data rate will be around 2kbytes/second and could run for hours).
And then how to open a binary file and read the data a byte at a time and process it.
I've found examples appending strings, (not that I've got any of the examples to work yet) but my data may have nulls in it so I'd expect that to break the string handling anyway.

Is my first task a bridge too far?

Any guidance would be appreciated and I thank you sincerely for your time and patience.