dim <any variable>[<byte or int x_dim> [, <byte or int y_dim>]] [fast]

The DIM directive defines a variable or an array. See the Arrays page for more information about arrays.

Variables do not need to be predefined, but the DIM directive allows you to do so. For example you can use DIM to define fast variables:

dim myFastVar fast

Read more about fast variables on the Variables page.