Intel 80286, 80287 manual ii.t

NUMERIC PROGRAMMING EXAMPLES

iAPX286 MACRO ASSEMBLER

LOC OBJ

0007 98

aooa 8S46FA

0000 2DCl

0000 7722

OODF DF46FC 00E2 SaFe!

00E4 BOEAFE aOE7 DB6EFO

OOEA D9FD

aOEe 0001 OOEe D9FC

OOFO 0809

OOFe! 9BDD7EFE 00F6 F146FE0040

00F9 7550

OOFO 0008

DOFF BnOb

0101

80287	Floating-Point to is-Digit ASCII		Conversion	10: 12: 38 0'1'/25/83 PAGE
LINE	SOURCE
32.	i'Li/ait			Wait for power_ten to be valid
323	mov	,ax,poLlla,,_ten	I	Get powe" of tan of value
3.4	sub	ax, ex	I	Form scaling factor nacaIl5.,,1,1 in ax
32S	J,a	adJust_"luult		Jump if number will not fit
326

327The number is betwaen 1 ,and 10**<field_lIirel.

328Test if it is an intega".

3 ••	HId	pOLlIa" _ two
330			I Ra .. to"e original number
331	mov	II i. d x		S.va "eturn valua
332	.ub	dl. NORMAL-EXACT	I	Conv."t to exact ".tu"n v .. lue
333	fl'	fraction	I	Form	full	value.	this 1s	safe here
334	fscal a
33'	'"f"ndint	,t (1)		Copy	value	fo" comparl!
336			J	Tast if its an intege"
337	fcomp		I	Compa"a values
338	fstsw	status	J	Save	status
33'	test	status.4000H		C3a 1	implil!S it was an integl!"
340	J"'	c onvl!rt_i ntagar
341
342	htp	st(Ol	J Remove non integer value
343		d x. IIi	I	Restore original			return	value
344

345Sc,ala the number to Ll/ithin the range allowed by the BCD form,at.

346The scaling operation 5hould produce ,a numb.r within one decimal order

347of magnitUde of the largut decim.!ll number repra .. ntabla within the

348given string width.

34.	,	nl! seal ing power of ten value is in u .
350
351

352adJu .. t_ruult:

0101 8907

0103 F708

0105 EBOOOO

0108 OD6EFO 010/3 DEC9

0100 813FI

0101=' 01E6 0111 01E6

011:3 0lE6

0115 OF46FC

0118 DEC2

OIIA D9FD

011C 0009

354	moy
33.	no,
306
357	call
358	fl'
339
360	fmul

361moY

362'h 1

363'h 1

364.h 1

365Hid

366faddp

367flcale

368htp

word ptr Cbx~ ••u	I	s . t	initial powe" of ten return value
	j Subtract one 'or each order 0'
	J magnitude the vo!!Ilue i!li scaled by
		Scaling flactor is returned as uponent
Practlen		and	fraction
		Q"t	.p"action
sit ex		Combine			fractions
	I	Form pOlller of ten of! the maximum
si.1	j	BCD value to fit in the string
\ii.t	)	Indu		in	s1
si. 1
power _two	j	Combine			powlfrs of two
st(2). lit		Form full value. exponent wall saile
	J	Remove		exponent

011E

011E 2EDC940eoo

0123 9BDFEO

0126 A90041

0129 750C

0129 2EOE360000

0130 BaE2FD 01:33 FF07

0135 E814

0137

0137 2EOC940000

013C 9DDFEO

013F A90001

0142 7401

0144 :2EOEOeOOOO

0149 FFOF

0149

0149 D9FC

0140

0140 OF76FO

0150 13E0800

370Tl!st the adJu.t.d value against a tablli! of t'~act powers of tt!n.

371Til. combined er"or' of thE!' magnitude IIstimatl! and power function ca.,

372ret.ult in a value one ordl'r of! magnitude too small 01" too large to fit

373corrl!ctly in ,the BCD Held. To handle thi!l pT'obhm. pretest the

37.	,	adJUsted valull> if it is too small 01' large. than adJust it by ten and
375		adJust th. powe" of ten value
376

377testJower:

37.f!com power_tableCsiJ+type power_table) Compare against exact power

380		.,		J	entry.			U!ie thf! ne~t entry since cx
381				J	has been decremented by one
382	fstsw			)	No	lIIait		is necessart,!
383	test	ax. 4100H		)	If	C3	-	CO .. 0 than too big
38.	J"'	test_fo" _sm,all
38.
386	f:Ldiv	const10			Elu		adJust		value
387	an'	d 1. not EXACT			Rli!mova			axact	fllag
388	in'	word ptr	tb xJ	I	AdJust power of tan value
39.	Jmp	.ho"t; in_ranga		J	Convart the value to a BCD int.g.r
3.,
0
39.
3.3		pOWIi!1"_hbhCsiJ		j	Test		relative size
394		..			No	wait		is naca.sart,!
39.		1U.IOOH			If! CO - 0 than st(O) >- low.,. bound
396		1n_range		I	Conv.rt tha valua to a BCD intager
397				"
399	Umul	constiO			AdJust valu. into range
39'	dac	LIIo"d pt,.	Cbx~		AdJu.t powar of t.n valua
400

401

40.

403flrndint

40SA.... rt: 0 <- TOS <- 999.999.999.999.999.999

406	J	The TOS number will ba ... c:tll,l repraunhble in 19 digit BCD format.
407	,

408convart_i nteg.,.:

410
411
41.	Whih the .to,..e BCD "uns ... etup ragi . tns for the conversion to

413ASCII.

415 I Initial BCD index valua

Figure 4-6. Floating-Point to ASCII Conversion Routine (Cont'd.)

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