Extended-precision 
Extended-precision variables require 10 bytes 
 of storage each.  They have a range of approximately  +/- 3.4*10^-4932 
 to 1.2*10^4932, and offer 18 digits of precision.  All 18 digits 
 can be "displayed" using the extended STR$ 
 format (eg, STR$(var##,18)).
Extended-precision variables are identified 
 by adding two Number symbols following a variable name (i.e., var##) 
 or by using the DEFEXT 
 statement..  You can also declare Extended-precision variables using 
 the EXT or EXTENDED keywords with the DIM 
 statement.  For example:
DIM I AS EXT
DIM J AS EXTENDED
See Also