TI -82 Manual Book page 151

Accessing List Dimensions with dim
dim (dimension) returns the length (number of elements) of list.
dim list
Creating a List with dim
is used with ¿ to create new listname with dimension length. The
dim
elements are zeros.
!dim
length
Redimensioning a List with dim
is used with ¿ to redimension existing listname to dimension
dim
length.
¦
The elements in the old listname that are within the new dimension are
not changed.
¦
Any additional elements that are created are zeros.
!dim
length
listname
listname
Lists 11-7