User's Manual

iAPX2Sb MACRO ASSEMBLER
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NUMERIC PROGRAMMING EXAMPLES
80287 Floating-Point to IS-Digit ASCII Conv~1"6ion
10: 12: 38 09/25/83 PAGE
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SOURCE
If the given number Ula!> zero, the ASCII string will contain a sign
and a single zero chacter. The value string_size indicates. the total
length of the ASCII string including the sign character. StringeD) will
alwal,ls hold the sign. It is possible for string_sile to be less than
field_sileo This occurs for zeroes or integer values. A pauedo zero
will return a special return code. The denormal count will indicate
the power of two original III associated with the vlillue. The power of
ten and ASCII string will be as if the value was an o'f'dinar~ lero.
This subroutine is accurate up to a maximum of 18 decimal diilits for
integers. Integer values will have a decimal power of zero associated
with them. For non integers. the result will be accurate to within 2
dIJcimal digits of the 16th decimal place (double precision>. The
exponentiate instruction is also used for scaling thIJ value into the
range acceptable for the BCD data t~pe. The rounding mode in effect
on entrv to the subroutine is used for thIJ conversion.
The following regist.~rs are not transpart'nt:
Dt'fine the stack lallout.
,
bp_save
'0·
word ptr [bpJ
es_save
'0·
returnJtr
'0·
power -ptr
'0·
field_size
'0·
SileJltr
'0·
string-ptr
'0·
denormal_ptr
'0·
bp_save + size bp_save
es_save + size es_save
return_ptr + size returnJltr
powerJltr + sile power_ptr
field_size + size field_sil,e
size_ptr + size sizeJltr
string_ptr + size stringJtr
parms_sl ze
•
,
BCD_DIGITS
WORD_SIZE
BCD_SIZE
MINUS
NAN
'0·
size power_ptr + !;ize field_size + size size-ptr +
size stringJltr + size denormalJtT·
Define constants used
'0·
18
,
Number of iigits in bcd_value
eo·
2
'0·
10
eo·
I
,
Define return values
'0·
4
,
The exact values chosen here are
INFINITY
'0.
6
important.
The\! must correspond to
INDEFINITE
'0·
3
,
the possible return v .. lu •• and
b. in
PSUEDO_ZERO
'0·
8 the same numeric
order as tested b~
INVALID
ZERO
DENORMAL
UNNORMAL
NORMAL
EXACT
,
status
power _two
power _ten
bcd_value
bcd_byte
fr.c t i on
con.tlD
'0·
-2 the program.
'0· -.
'0·
-6
'0·
-8
'0·
0
'0·
2
Define la~out of temporOlr\! storage area.
.,.
'0·
'0·
'0·
eo·
'0·
word ptr tbp-WORD_SIZEl
status - WORD_SIZE
power_two - WORD_SIZE
tbyte ptr power _ten - BCD_SIZE
bl,lte ptr bcd_value
bcd_value
size status + size power_two + 6ize power_ten
+ size bcd_v.lue
segment e1" pub I ic
ext1"n power_tab I.: q,ward
Constant. used blJ this function.
even
d. 10
j Optimize for 16 bits
J AdJustment value floT" too big BCD
Convert the C3.C2.Cl.CO encoding fir om tos_stOltus into meaningful bit
fllags OInd values.
db
UNNORMAL. NAN. VNNORMAl. + MINUS. NAN + MINUS.
NORMAL. INFINITY. NORMAL + MINUS. INFINITY + MINUS.
ZERO, INVAl.lD.
ZERO + MINUS, INVALID,
DENORMAL, INVALID, OENORMAL + MINUS. INVALID
Figure 4-6. Floating-Point to ASCII Conversion Routine (Cont'd.)
4-8