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NUMERIC PROGRAMMING EXAMPLES
80287
Floating-Point
to
IS-Digit
ASCII
Conversion
10: 12:
89
09/25/83
PAGE
LINE
228
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28.
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291
2'2
:293
2
••
29'
2'6
2'7
2.8
2.,
300
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30'
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321
SOURCE
fxtratt
cmp
dl,UNNDRMAL
Jb
normal_value
sub
d
1,
UNNORMAL-NORMAL
Normalize
the
fraction.
the
denormal
count
value.
Assert:
0
<'"
ST(O)
(
1.0
-Fld 1
J
Separate
exponent
f'T'om
significand
,
Test
for
unnormal
value
Return
normal
status
with
correct
Sign
adJust
the
power
of
two
in
ST(1)
and
1t.et
,
Load
constant
to
normalize
fraction
norma
1 i z
e_frac
t
ion:
fadd
st(1).1t.t
hub
f
xc
h
fi1t.t
word
ptr
CdiJ
faddp
st
(2).
st
ne-g
word
ph
CdiJ
Jnz
not_psuedo_zero
Set
integer
bit
in
fraction
j
Form
normalized
fraction
in
ST(O)
J
Power
of
two
Held
will
be
negative
of
denormal
count
j
Put
denormal
count
in
ST(O)
J
Put
negative
of
dl!'normal
count
in
memorl,l
Form
correct
power
of
two
in
stt!)
OK
to
use
word
ptr
CdiJ
now
Form
positive
denormt!ll
count
A
psuedo
zero
will
appear
an
unnormal
numbeor. When
attemptinll
to
normalia
it.
the
resultant
fraction
field
will
be
zero.
Perfo~minll
an
f'xtrBct
on
zero
will
yield
a
zero
exponent
value.
.
f~ch
)
Put
power
of
tllJO
value
in
!OttO)
Fistp
word
ptr
CdiJ
Set
denorm<ll
count
to
power
of'
two
value
Word
ph
(diJ
is
not
u!;ed by
convert
integer.
OK
to
letJve
running
!:tub
dl,
NDRMAL-P5UEDO_ZERD
,Set
return
value
saving
thf!
sign
bit
Jmp
convert_i.nteger
)
Put
zero
value
into
memory
The
number
is
a
real
zero.
'iet
the
return
value
and
setup
for
conversion
to
BCD
d
1,
ZERO-NORMAL
convert_integer
,
Convert
<;t.3tlIS
to
normal
v<'Jlu!'
i
Treat
the:
l~ro
as
an
i.ntE!geT'
Th.
nUmbllr
is
a
dllnoTmal.
FXTRACT
will
not
wOTk
correctly
in
tht.
elutt.
To
corrttetlu
slIparate
the
eKponllnt
and
fraction,
add
a
fixed
J
constant
to
tht'
exponent
to
guarantee
thll
rellult
il
not
a
denormal.
,
found_d
enorma
1:
,
fld
1
heh
fpram
htract
j
PTeparl!
to. bump
axponent
ForeD
denormal
to
smallelit
represllntable
utendlld
raal
-Format
exponent
)
This
will
work
corrllctly
now
The
power
of
the
original
dllnoT'mal
valu.
n.n
baen
safely
isohtad.
Check
if
the
fraction
value
is
an
unnormal.
ham
htsw
hch
heh
"b
t!!!!t
J'
fstp
atC:!)
dl.
DENORMAL-NORMAI..
8K,4400H
norma
1 i
:re_fTac
t i
on
stCO)
SII'
if
the
fraction
is
an
unnormal
Save
80287
statu.
In
CPU
AX
rIg
for
later
I
Put
uponent
in
9T(O)
,
Put
1.
~
into
SHO),
uponant
in
9T(2)
j
Return
normal
status
with
correct
lign
j
See
if!
C:3-C:!"O imp
ling
unnormal
aT'
NAN
j Jump
if
-Fraction
is
an
unnormal
j
Remov.
unnecessary
1. 0
from
lIteO)
Calculatt
the
d.eimal
magnitude
a"oelated
with
this
numb
Ill'
to
lIIithin
one
order.
Tnt.
error
lIIi1l
allllays
bll
inevihbh
due
to
rounding
and
lost
pr.ttlion.
A.
a
rlSult,
we
will
delibarfttwly
fail
to
considar
the
LOOIO
of
the
fraction
valua
in
calculating
thll
oT'dn.
Since
th
hattion
will
alwaYI
be
1
<-
F
<:!,
its
L.DOIO
will
not
change
thll
baSic
accurilcl/
oft
the
function.
To
get
thll
decimal
order
of
magnitude.
limply
multipl1J
tha
power
of
two
bl,l L.OQ10(2)
and
truncate
thll
ruult
to
.an
integar.
normal_valu.:
notJlIu.do_:rero:
fltp
fTacUon
fiat
POWtT'_two
Udlg2
fmul
fhtp
power_tan
tlsve
,;;nll
Tr.1;;~I.I;U'
ii.."";
;
...
,
~
........
Save
power
of
two
Qet
L.OQ10(2)
Pow.r_two
is
noUl
saf.
to
us.
I
Form
LOG10(of
exponent
of
number)
j
AnI,!
rounding
moda
will
work
harll
Check
if
the
magnitude
of
thll
number
rule.
out
treating
it
al
integllr.
CX
ha.
the
maximum
number
of
decimal
digits
allowed.
Figure 4-6. Floating-Point
to
ASCII Conversion Routine (Cont'd.)
4-10