# fixmul (3) - Linux Manuals

## fixmul: Multiplies two fixed point values together. Allegro game programming library.

## NAME

fixmul - Multiplies two fixed point values together. Allegro game programming library.## SYNOPSIS

**#include <allegro.h>**

**fixed fixmul(fixed x, fixed y);**

## DESCRIPTION

A fixed point value can be multiplied or divided by an integer with the normal `*' and `/' operators. To multiply two fixed point values, though, you must use this function.If an overflow occurs, `errno' will be set and the maximum possible value will be returned, but `errno' is not cleared if the operation is successful. This means that if you are going to test for overflow you should set `errno=0' before calling fixmul(). Example:

fixed result; /* This will put 30000 into `result'. */ result = fixmul(itofix(10), itofix(3000)); /* But this overflows, and sets `errno'. */ result = fixmul(itofix(100), itofix(3000)); ASSERT(!errno);

## RETURN VALUE

Returns the clamped result of multiplying `x' by `y', setting `errno' to ERANGE if there was an overflow.## SEE ALSO

**fixadd**(3),

**fixsub**(3),

**fixdiv**(3),

**ex3buf**(3),

**excustom**(3),

**exfixed**(3),

**exspline**(3),

**exstars**(3),

**exupdate**(3)