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 · Accepted 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

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

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

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

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

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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