HP 3000 Manuals

HP FORTRAN 77/iX Programmer's Guide

Integer Overflow Checking 

Integer overflow checking is turned on for 16-bit and 32-bit arithmetic
to be compatible with FORTRAN 77/V. The 16-bit integer overflow checking
generates three extra instructions to check the overflow for loads and
stores.  The 32-bit overflow checking generates overflow instructions
that cannot be optimized.  To turn off integer overflow checking, specify
$CHECK_OVERFLOW INTEGER OFF.

MPE/iX 5.0 Documentation