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FFP floating-point variables are defined within C by the float or FLOAT
directive. In assembly language they are simply defined by a DC.L/DS.L
statement. All FFP floating-point variables are defined as 32-bit entities
(longwords) with the following format:

        |                                             |
        | 31          23          15          7       |

The mantissa is considered to be a binary fixed-point fraction; except for
0, it is always normalized (the mantissa is shifted over and the exponent
adjusted, so that the mantissa has a 1 bit in its highest position).
Thus, it represents a value of less than 1 but greater than or equal to

The sign bit is reset (0) for a positive value and set (1) for a negative

The exponent is the power of two needed to correctly position the mantissa
to reflect the number's true arithmetic value.  It is held in excess-64
notation, which means that the two's-complement values are adjusted upward
by 64, thus changing $40 (-64) through $3F (+63) to $00 through $7F.  This
facilitates comparisons among floating-point values.

The value of 0 is defined as all 32 bits being 0s.  The sign, exponent,
and mantissa are entirely cleared.  Thus, 0s are always treated as

The range allowed by this format is as follows:


         9.22337177 * 10^18 > +VALUE > 5.42101070 * 10^-20
        -9.22337177 * 10^18 < -VALUE < -2.71050535 * 10^-20


         .FFFFFF * 2^63 > +VALUE > .800000 * 2^-63
        -.FFFFFF * 2^63 < -VALUE < -.800000 * 2^-64

Remember that you cannot perform any arithmetic on these variables without
using the fast floating-point libraries.  The formats of the variables are
incompatible with the arithmetic format of C-generated code; hence, all
floating-point operations are performed through function calls.