The arithmetic operators (+, -, *, /) can produce results that are outside the range of possible values for the numeric type involved. You should refer to the section on a particular operator for details, but in general:
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Integer arithmetic overflow either throws an OverflowException or discards the most significant bits of the result. Integer division by zero always throws a DivideByZeroException.
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Floating-point arithmetic overflow or division by zero never throws an exception, because floating-point types are based on IEEE 754 and so have provisions for representing infinity and NaN (Not a Number).
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Decimal arithmetic overflow always throws an OverflowException. Decimal division by zero always throws a DivideByZeroException.
When integer overflow occurs, what happens depends on the execution context, which can be checked or unchecked. In a checked context, an OverflowException is thrown. In an unchecked context, the most significant bits of the result are discarded and execution continues. Thus, C# gives you the choice of handling or ignoring overflow.
In addition to the arithmetic operators, integral-type to integral-type casts can cause overflow, for example, casting a long to an int, and are subject to checked or unchecked execution. However, bitwise operators and shift operators never cause overflow.