;-------------------------float routine begins--------------------------+
; from BLUEBOOK OF ASSEMBLY ROUTINES FOR IBM PC & XT.
;         page : 109
;
; NAME  FLOAT
;
; ROUTINE FOR Conversion from 16-Bit Integer to Floating Point
;
; FUNCTION: This routine converts an unsigned 16-bit binary number to a
; single precision binary floating point number.
;
; INPUT: Upon entry DX contains an unsigned 16-bit binary number
;
; OUTPUT: Upon exit SFPBUFF contains a single precision floating point
; number.  The single precision floating point number has a 24-bit binary
; mantissa, a sign bit, and an 8-bit exponent biased by 128.
;
; REGISTERS USED:  No registers are modified.  DX is used for input.
;
; SEGMENTS REFERENCED:  The data segment contains storage for the variable
; SFPBUFF and the message INTERNAL.
;
; ROUTINES CALLED:  STDMESSOUT, HEX16OUT, STDSPACE (All for debugging).
;
; SPECIAL NOTES: Equates are used to shorten address fields.
;
; ROUTINE TO CONVERT FROM INTERNAL INTEGER TO INTERNAL FLOATING POINT
;
float	proc	far
;
; the number is in DX
;
	push	dx		; save registers
	push	cx
	push	ax
;
	mov	ax,0		; extend to 32 bits
	cmp	dx,0		; check if zero
	jz	float4
;
float1:
	mox	cx,9800h	; initialize exponent and sign
; shift left until normalized
;
float2:
	test	ax,0080h	; done yet ?
	jnz	float3		; exit if true
	sal	dx,1		; shift all bits left if not
	rcl	ax,1		; carry on
	dec	ch		; decrement the exponent
	jmp	float2
;
float3:
;
; pack it in
	and	ax,007Fh	; just the mantissa
	or	ax,cx		; exponent and sign
;
float4:
	mov	sfpbuffw0,dx	; put lower part into place
	mov	sfpbuffw2,ax	; put upper part into place
;
; show hex for debugging
	lea	si,internal	; point to message
	call	stdmessout	; send message
;
	mov	dx,sfpbuffw2	; upper word
	call	hex16out	; show it
;
	call	stdspace	; skip space
;
	pop	ax		; restore registers
	pop	cx
	pop	dx
	ret			; return
;
float	endp
;-------------------------float routine ends---------------------------+