NAME

       al_fixed - Allegro 5 API

SYNOPSIS

              #include <allegro5/allegro.h>

              typedef int32_t al_fixed;

DESCRIPTION

       A fixed point number.

       Allegro  provides some routines for working with fixed point numbers, and defines the type
       al_fixed to be a signed 32-bit integer.  The high word is used for the  integer  part  and
       the  low word for the fraction, giving a range of -32768 to 32767 and an accuracy of about
       four or five decimal places.  Fixed  point  numbers  can  be  assigned,  compared,  added,
       subtracted,  negated  and shifted (for multiplying or dividing by powers of two) using the
       normal integer operators, but you should take  care  to  use  the  appropriate  conversion
       routines  when  mixing  fixed  point  with  integer  or  floating  point  values.  Writing
       fixed_point_1 + fixed_point_2 is OK, but fixed_point + integer is not.

       The only advantage of fixed point math routines is that you don't require a floating point
       coprocessor to use them.  This was great in the time period of i386 and i486 machines, but
       stopped being so useful with the coming of the Pentium class of processors.  From  Pentium
       onwards, CPUs have increased their strength in floating point operations, equaling or even
       surpassing integer math performance.  However, many embedded processors have  no  FPUs  so
       fixed point maths can still be useful there.

       Depending  on the type of operations your program may need, using floating point types may
       be faster than fixed types if you are targeting a specific machine class.