Editing Fixed-point arithmetic (section)

===Overflow===
Overflow happens when the result of an arithmetic operation is too large to be stored in the designated destination area. In addition and subtraction, the result may require one bit more than the operands. In multiplication of two unsigned integers with ''m'' and ''n'' bits, the result may have ''m''+''n'' bits.

In case of overflow, the high-order bits are usually lost, as the un-scaled integer gets reduced modulo 2<sup>''n''</sup> where ''n'' is the size of the storage area. The sign bit, in particular, is lost, which may radically change the sign and the magnitude of the value.

Some processors can set a hardware [[overflow flag]] and/or generate an [[Exception handling|exception]] on the occurrence of an overflow.  Some processors may instead provide [[saturation arithmetic]]: if the result of an addition or subtraction were to overflow, they store instead the value with the largest magnitude that can fit in the receiving area and has the correct sign.{{cn|date=July 2021}} 

However, these features are not very useful in practice; it is generally easier and safer to select scaling factors and word sizes so as to exclude the possibility of overflow, or to check the operands for excessive values before executing the operation.