язык точной арифметики (precision arithmetic language)
Последствия ошибок (Consequences of errors)
If any file operand is specified and the named file cannot be
accessed, bc shall write a diagnostic message to standard error
and terminate without any further action.
In an interactive invocation of bc, the utility should print an
error message and recover following any error in the input. In a
non-interactive invocation of bc, invalid input causes undefined
behavior.
The following sections are informative.
