What is the behavior of integer division

Question

For example   int result   result   125 100    or   result   43 100    Will result always be the floor of the division  What is the defined behavior

User · Answer

Dirkgently gives an excellent description of integer division in C99, but you should also know that in C89 integer division with a negative operand has an implementation-defined direction.

From the ANSI C draft (3.3.5):

If either operand is negative, whether the result of the / operator is the largest integer less than the algebraic quotient or the smallest integer greater than the algebraic quotient is implementation-defined, as is the sign of the result of the % operator. If the quotient a/b is representable, the expression (a/b)*b + a%b shall equal a.

So watch out with negative numbers when you are stuck with a C89 compiler.

It's a fun fact that C99 chose truncation towards zero because that was how FORTRAN did it. See this message on comp.std.c.

User · Answer

Yes  the result is always truncated towards zero  It will round towards the smallest absolute value   -5   2   -2  5   2    2   For unsigned and non-negative signed values  this is the same as floor  rounding towards -Infinity

User · Answer

I know people have answered your question but in layman terms   5   2   2   since both 5 and 2 are integers and integers division always truncates decimals  5 0   2 or 5   2 0 or 5 0  2 0   2 5   here either 5 or 2 or both has decimal hence the quotient you will get will be in decimal

User · Answer

Will result always be the floor of the division  What is the defined behavior   Not quite  It rounds toward 0  rather than flooring   6 5 5 Multiplicative operators   6 When integers are divided  the result of the   operator is the algebraic quotient with any fractional part discarded 88  If the quotient a b is representable  the expression  a b  b   a b shall equal a   and the corresponding footnote    This is often called       truncation toward zero          Of course two points to note are   3 The usual arithmetic conversions are performed on the operands   and   5 The result of the   operator is the quotient from the division of the first operand by the second  the result of the   operator is the remainder  In both operations  if the value of the second operand is zero  the behavior is undefined    Note  Emphasis mine

User · Answer

Will result always be the floor of the division    No  The result varies  but variation happens only for negative values      What is the defined behavior    To make it clear floor rounds towards negative infinity while integer division rounds towards zero  truncates   For positive values they are the same  int integerDivisionResultPositive  125 100     1 double flooringResultPositive  floor 125 0 100 0     1 0   For negative value this is different  int integerDivisionResultNegative  -125 100    -1 double flooringResultNegative  floor -125 0 100 0     -2 0

User · Answer

Where the result is negative  C truncates towards 0 rather than flooring - I learnt this reading about why Python integer division always floors here  Why Python s Integer Division Floors

[c] What is the behavior of integer division?

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