Dim array()

DIM sets the maximum size of an array.  Any array can be dimensioned to have as many elements as memory allows.  If an array is not DIMensioned explicitly, then the array will be limited to 11 elements, 0 to 10.  Non DIMensioned double subscript arrays will be limited to 121 elements 0 to 10 by 0 to 10.  The DIM statement can be followed by a list of arrays to be dimensioned, separated by commas.

Redim array()

This redimensions an already dimensioned array and clears all elements to zero (or to an empty string).  This can be very useful for writing apps that have data sets of unknown size.  If you dimension arrays that are extra large to make sure you can hold data, but only have a small set of data, then all the space you reserved is wasted.  This hurts performance, because memory is set aside for the number of elements in the DIM statement.

