There is a close correspondence between the indexes in a $1$D array and $2$D array of the same size.

For example, suppose a program has the following two array declarations:

const int SIZE $=4,x=2,Y=2$;

int arr$1[$SIZE$]$;

int arr$2[x][Y]$;

Both the $1$D array and the $2$D array have four indexes $($subscripts$).$

For example, suppose the numbers $11,22,33,$ and $44$ are being stored. The $1$D array would look like this:

$11,22,33,44$

And the $2$D array would look like this:

$1122$

$33,44$