Category : Assembly Language Source Code
Archive   : ASM-SUBR.ZIP
Filename : FPOUT

;-------------------------fpout routine begins--------------------------+
; from BLUEBOOK OF ASSEMBLY ROUTINES FOR IBM PC & XT.
; page : 104
;
; NAME FPOUT
;
; ROUTINE FOR Conversion From Internal To External Floating Point
;
; FUNCTION: This routine displays a single precision floating point
; number on the standard output device as a decimal floating point number.
;
; INPUT: Upon entry a single precision floating point number is is SFPBUFF.
; The single precision floating point number has a 24-bit binary mantissa,
; a sign bit and an 8-bit exponent biased by 128 (Fig 5-3).
;
; OUTPUT: The individual characters of a decimal floating point number
; are sent out through the standard output device. The decimal floating
; point number has a sign character which is blank or minus, followed by
; decimal digits of the mantissa with one embedded decimal point to the
; right of the first significant digit. Following the mantissa is an
; exponent which starts with the letter 'E', then a sign, then a decimal
; number (Fig 5-4).
;
; REGISTERS USED: AX, BX, CX, DX, SI and DI are modified.
;
; SEGMENTS REFERENCED: The data segment contains storage for the variables
; DECBUFF, DECSIGN, DECEXP, FPTMP1 and SFPBUFF.
;
; ROUTINES CALLED: STDOUT, SFP2TFP, DECHALF, DECDOUBL, DECNORM, TDECSHOW
;
; SPECIAL NOTES: Equates are used to shorten address fields.
;
; ROUTINE TO CONVERT FROM INTERNAL FLOATING POINT TO ASCII FLOATING POINT
;
fpout proc far
;
push di ; save registers
push si
push dx
push bx
push cx
push ax
;
; check for zero as a specific case
mov ax,sfpbuffw0 ; get low word
or ax,sfpbuffw2 ; get high word
jnz fpout1 ; go on if not zero
;
mov al,'0' ; make a zero
call stdout ; send it out
jmp fpout6 ; and exit
;
fpout1:
; convert from single precision to temp floating point
call sfp2tfp ; convert to temp format
;
; initialize exponent for unnormal position
mov decexp,21 ; exp = 21 for start
;
; set the sign
mov al,fptemp1b10 ; get sign
mov decsign,al ; put it away
;
; convert a mantissa to a decimal string
lea si,fptemp1 ; si points to fptemp1
lea di,decbuff ; di points to decbuff
call bi8e2dec ; make decimal string
;
; check sign of binary exponent
mov cx,fptemp1w11 ; get the binary exponent
sub cx,72 ; biased by -72
cmp cx,0 ; check its sign
jl fpout2 ; if negative
jg fpout4 ; if positive
jmp fpout5 ; if zero
;
fpout2:
; binary exponent is negative
neg cx ; absolute value of exponent
;
fpout3:
push cx ; save count = binary exponent
;
; divide by 2
lea di,decbuff ; point to decbuff
call dechalf ; divide by two
;
; normalize
lea di,decbuff ; point to decbuff
call decnorm ; normalize
;
pop cx ; restore count
loop fpout3
;
jmp fpout5 ; end of case
;
; binary exponent is positive
;
fpout4:
push cx ; save count = binary exponent
;
; multiply by two
lea di,decbuff ; point to decbuff
call decdoubl ; multiply by two
;
; normalize
lea di,decbuff ; point to decbuff
call decnorm ; renormalize
;
pop cx ; restore count
loop fpout4
;
jmp fpout5 ; end of case
;
fpout5:
;
; output the number
call tdecshow ; display the number
;
fpout6:
pop ax ; restore registers
pop cx
pop bx
pop dx
pop si
pop di
;
ret ; return
'
fpout endp
;-------------------------fpout routine ends---------------------------+