AT&T 6300 Programmer's Manual page 184

CDBL
Function
Syntax
Example
7-28
Converts a given numeric expression to a
double precision number.
CDBL (numexp)
10 A=454.67
20 PRINT A;CDBL(A)
RUN
454.67 454.6700134277344
Ok
Note: A and CDBL (A) do not have precisely
the same value due to the difference in the way
that single and double precision numbers are
stored internally. For more information, see
the Appendix on Advanced Features.