Q38274: Single Precision "Overflow" when Nearing Divide By Zero;10E-38
Article: Q38274 Product(s): See article Version(s): 3.00 4.00 4.00b 4.50 Operating System(s): MS-DOS Keyword(s): ENDUSER | B_BasicCom | mspl13_basic Last Modified: 9-DEC-1988 The code example below produces an "OVERFLOW" error at n = 38 for QuickBASIC Versions 3.00, 4.00, and 4.00b, and BASIC Compiler Versions 6.00 and 6.00b for MS-DOS and OS/2. The overflow occurs as you divide by ever larger numbers and approach the limits of the negative exponent for single precision. The program may overflow at different places in other versions of BASIC. To work around the "Overflow" error, use at least one double precision variable or constant in the expression before assigning to the variable. The following code example gives an "Overflow" error at n = 38: FOR n = 1 TO 100 x# = 1 / 10 ^ n PRINT n, x# NEXT In the above program, the expression 1/10^n is optimized to use single precision, since the most precise argument in the expression is n, which defaults to single precision. To avoid the overflow of the negative single precision exponent, change n to double precision (n#). This forces the expression 1/10^n# to be stored in a double precision temporary storage area before being assigned to x#: FOR n# = 1 TO 100 ' This program runs fine from n#=1 through 100. x# = 1 / 10 ^ n# PRINT n#, x# NEXT
THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.
Copyright Microsoft Corporation 1986-2002.