Essential Books

Division by zero

suggest change 
int x = 0;
int y = 5 / x;  /* integer division */

or 

double x = 0.0;
double y = 5.0 / x;  /* floating point division */

or 

int x = 0;
int y = 5 % x;  /* modulo operation */

For the second line in each example, where the value of the second operand (x) is zero, the behaviour is undefined.

Note that most implementations of floating point math will follow a standard (e.g. IEEE 754), in which case operations like divide-by-zero will have consistent results (e.g., INFINITY) even though the C standard says the operation is undefined.

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Undefined behavior:
* Undefined behavior
* Dereferencing a pointer to variable beyond its lifetime
* Copying overlapping memory
* Signed integer overflow
* Use of an uninitialized variable
* Read value of pointer that was freed
* Data race
* Modify string literal
* Using incorrect format specifier in printf
* Modifying any object more than once between two sequence points
* Passing a null pointer to printf s conversion
* Bit shifting using negative counts or beyond the width of the type
* Freeing memory twice
* Accessing memory beyond allocated chunk
* Returning from a function thats declared with Noreturn or noreturn function specifier
* Addition or subtraction of pointer not properly bounded
* Modifying a const variable using a pointer
* Dereferencing a null pointer
* Reading an uninitialized object that is not backed by memory
* Using fflush on an input stream
* Division by zero
* Missing return statement in value returning function
* Inconsistent linkage of identifiers
* Conversion between pointer types produces incorrectly aligned result
* Modifying the string returned by getenv strerror and setlocale functions
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