reading multiple arrays loop

I have a program that reads in a 2d array of data of a text file everytime
you click a button.  I need to loop this so it keeps adding to
the previous array of data until the program has finished.  I know
you need a for loop and ****ft registers but i am still confused on the
implementation of it.
 
For example:  text contains:
AB
AB
AB
AB
 
on the VERY next click  i want it to read and store
ABAB
ABAB
ABAB
ABAB
 
so what comes after the array