Why is X % 0 an Invalid Expression in Programming?

Division and Modulo Operations with Zero Divisors

In programming, the modulo operator (%) calculates the remainder when one number is divided by another. However, when the divisor is zero, an error is encountered.

Why is X % 0 an Invalid Expression?

Logically, one might assume that X % 0 should return the remainder, which is X. However, according to the C Standard, it is undefined behavior to perform either division (/) or modulo (%) operations with a zero divisor.

Undefined Behavior

Section 5.6/4 of the C Standard explicitly states that if the second operand of / or % is zero, the behavior is undefined. This means that the result of X % 0 is unpredictable and may vary depending on the system and compiler implementation.

Example of Undefined Behavior

Consider the following code:

int x = 10;
int result = x % 0; // Undefined behavior

In this example, the value of result is undefined and could result in a runtime error or other unpredictable consequences.

Implementation-Defined Behavior for Negative Operands

It's important to note that the behavior of the modulo operator for negative operands is implementation-defined. If both operands are non-negative, the remainder is non-negative. However, if one or both operands are negative, the sign of the remainder is unpredictable.

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