Let's say that you want to treat the appvar as a matrix with 5 columns and 4 rows. For the most part, memory in Axe is treated as a list, not a matrix, so we have to use a workaround to be able to use memory as a matrix.
So, we want a matrix. Because our matrix has sides of 4 and 5, the total amount of memory we want would be 20 bytes (or 40, if you use double-byte numbers).
We can create an appvar like this:
"appvNAME"->Str1
GetCalc(Str1,20)->P
You can get the 'appv' symbol by hitting [2ND] then [8].
To write to and access the 5th byte in the appvar, you would do this:
42->{P+4}
Disp {P+4}>Dec
(Remember that lists in computers start at zero: to access the 1st byte, do {P}, which is equal to {P+0}, and to access the last, 20th byte, do {P+19}).
However, if we chose to treat the appvar as a matrix, we can. The appvar won't be changed in any way, all we're doing is changing the way we access it.
I'm going to arrange the bytes in a block.
00 01 02 03 04
05 06 07 08 09
10 11 12 13 14
15 16 17 18 19
If we conceptualize the appvar like this, then we can use a short formula-thingy to input the row and column, and return the actual byte we want.
{ROW*LENGTH + COLUMN + POINTER}
So, if we want the byte at column 1, row 2, we would do this:
{2*5+1+P} == {11 + P}
Because this is computers, we treat the first rows/column as the zeroth row/column.
That might be a bit of a complicated answer: let me know if you need anything clarified.
