Real types
 ----------
A real type has a set of values that is a subset of real numbers, which can
be represented in floating-point notation with a fixed number of digits.

A value's floating-point notation normally is made up of three values--M, B,
and E--such that M x B E = N where B is always 2, and both M and E are
integral values within the real type's range.

Turbo Pascal provides five predefined real types. Each type has a specific
range and precision:

   Type     | Range               | Digits | Bytes
   ===============================================
   real     | 2.9e-39..1.7e38     | 11-12  |  6
   single   | 1.5e-45..3.4e38     |  7-8   |  4
   double   | 5.0e-324..1.7e308   | 15-16  |  8
   extended | 3.4e-4932..1.1e4932 | 19-20  | 10
   comp     | -9.2e18..9.2e18     | 19-20  |  8

Note: The comp type is a 64-bit integer. It holds only integral values
within the range (-2 63 + 1) to (2 63 - 1).

Turbo Pascal supports two models of floating-point code generation:
  - Software floating point, {$N-}
  - 80x87 floating point, {$N+}

You use the $N compiler directive to switch between the two models.

In the $N+ state, the $E compiler directive controls whether to include an
8087 software emulation library in the final program.

- eof -