Why Is X % 0 Invalid in C ?

Can't Mod Zero?

Why is the expression X % 0 invalid in programming languages like C ? Intuitively, one might expect it to return the remainder of X, similar to division.

According to the C Standard (2003), the behavior of / and % operators is undefined when the second operand (the divisor) is zero:

[...] If the second operand of / or % is zero the behavior is undefined [...]

Therefore, the following expressions invoke undefined behavior (UB):

X / 0; // UB
X % 0; // UB

This undefined behavior means that the exact result of these expressions is unpredictable and can vary depending on the specific compiler or implementation.

Additionally, it's important to note that the remainder of -5 % 2 is not simply the negative of 5 % 2. The sign of the remainder when both operands are non-positive is implementation-defined, not standardized.

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