Why Is X % 0 Invalid in Programming?

Can't Mod Zero? Why X % 0 Is Invalid

As programmers, we often rely on modulo operations to find remainders. However, performing X % 0 raises an error or produces unexpected behavior. Why is this so?

The Undefined Behavior

According to the C Standard (2003), X % 0 is an invalid expression. Section 5.6/4 states that:

"... If the second operand of / or % is zero, the behavior is undefined..."

Therefore, any code that attempts to perform this operation will invoke undefined behavior (UB).

Implementation-Defined Behavior

Another confusing behavior related to modulo operations involves negative numbers. For example, -5 % 2 may not always produce the same result as -(5 % 2). The standard specifies that:

"... If both operands are nonnegative, then the remainder is nonnegative; if not, the sign of the remainder is implementation-defined."

In other words, the behavior of modulo operations with negative numbers is not explicitly defined by the standard and can vary depending on the implementation.

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