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Apple II User Manual

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     - 3        81      A0 00 00
     - 4        81      80 00 00
     - 5        82      B0 00 00
     - 7        82      90 00 00
     -12        83      A0 00 00
     -15        83      88 00 00
     -17        84      BC 00 00
     -20        84      B0 00 00
     -60        85      88 00 00
FLOATING POINT SUBROUTINE DESCRIPTIONS
FCOMPL subroutine (address $F4A4)
Purpose: FCOMPL is used to negate floating point numbers.
Entry: A normalized or unnormalized value is in FP1 (floating point
accumulator 1).
Uses: NORM, RTLOG.
Exit: The value in FP1 is negated and then normalized to retain precision.
The 3-byte FP1 extension, E, may also be altered but FP2 and SIGN are not
disturbed.  The 6502 A-REG is altered and the X-REG is cleared.  The Y-REG
is not disturbed.
Caution: Attempting to negate -2^128 will result in an overflow since
+2^128 is not representable, and a jump to location $3F5 will be executed,
with the following contents in FP1.
      _____    _____    _____    _____
     |     |  |     |  |     |  |     |
FP1: |  0  |  | $80 |  |  0  |  |  0  |
     |_____|  |_____|  |_____|  |_____|
       X1       M1
Example: Prior to calling FCOMPL, FP1 contains +15.
      _____    _____    _____    _____
     |     |  |     |  |     |  |     |
FP1: | $83 |  | $78 |  |  0  |  |  0  |   (+15)
     |_____|  |_____|  |_____|  |_____|
       X1       M1
After calling FCOMPL as a subroutine, FP1 contains -15.
      _____    _____    _____    _____
     |     |  |     |  |     |  |     |
FP1: | $83 |  | $88 |  |  0  |  |  0  |   (+15)
     |_____|  |_____|  |_____|  |_____|
       X1       M1