I've never used pointers before and I'm finding the lingo a bit heavy.

Here's my problem.

I have a potentially very large matrix that looks like

1 2 3 4 5 6
2 3 4 5 6 7
3 4 5 6 7 8
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0

For my largest problem the matrix will have 11 columns and about
10,000,000 rows.

I'm only interested in the section that is nonzero but am not aware of
how to change the matrix size quickly and efficiently as more rows are
needed.  I was told that pointers maybe the way to go.  The example I
was shown was to declare a single column vector which represents my
first column i.e.

1
2
3
0
0
0
0

and then use a pointer that is 11 columns wide but grows to have the
same nunmber of rows as nonzero elements in the vector.

I'm not too sure how this can be done.  If anyone has any ideas or
sample code that would be great.