;; GetDec--translate a decimal number read from the keyboard
;;   into its equivalent binary number
;;
;;   Input:
;;	none
;;
;;   Output:
;;	If there is no error, the carry flag is clear and we have:
;;	ax = value translated
;;	If an error occurs, carry flag is set, ax is meaningless, and
;;
;;   The routine skips over leading white space--blanks and tabs
;;    it also handles backspace erasures unless the number gets too long
;;
;;   Errors: Overflow (number can't be expressed as 16 bit 2's complement)
;;
;;  Library source text from "Assembly Language for the IBM PC Family" by
;;   William B. Jones, (c) Copyright 1992, 1997, Scott/Jones Inc.
;;
INCLUDE PCMAC.INC
	.MODEL	SMALL
	.DATA
BUFFLEN	EQU	20
InBuff	DB	BUFFLEN+1 DUP (?)
	.CODE
	PUBLIC	GetDec
	EXTRN	Dec2Bin : NEAR
GetDec	PROC
	push	ds ;		Save registers to be used
	push	es
	push	cx
	push	dx ;		Used by _PutCh
	push	si
	push	di
	pushf	;		  ...and flags
	cld	;		Set direction flag upwards
	mov	ax, @data
	mov	ds, ax
	mov	es, ax
	lea	di, InBuff ;	The sign--Guess + = 0
	mov	cx, BUFFLEN ;	Character count
SkipWhiteSpace:
	_GetCh
	cmp	al, ' '
	je	SkipWhiteSpace
	cmp	al, 8 ;		Backspace
	jne	TryTab
DoBack:
	_PutCh	' ', 8 ;	Erase char
	jmp	SkipWhiteSpace
TryTab:
	cmp	al, 9 ;		Tab
	je	SkipWhiteSpace
	cmp	al, '+' ;	Number has been found; check for sign
	je	StoreIt
	cmp	al, '-'
	jne	CheckDig ;	Must be a digit
	jmp	StoreIt
NextDig:
	_GetCh
	cmp	al, 8 ;		Backspace
	jne	CheckDig
	inc	cx
	dec	di
	cmp	cx, BUFFLEN
	je	DoBack ;	We've erased the whole number
	_PutCh	' ', 8
	jmp	NextDig
CheckDig:
	cmp	al, '0' ;	Is the character a digit?
	jl	Done
	cmp	al, '9'
	jg	Done
StoreIt:
	stosb
	loop	NextDig
Error:
	popf
	stc	;		Set Carry to indicate error
	jmp	Restore ;	Restore regs and exit
Done:
	stosb
	cmp	al, 13 ;	If carriage return ...
	jne	NoLF
	_PutCh	10 ;		  ... also display line feed
NoLF:
	popf
	lea	si, InBuff
	call	Dec2Bin
Restore:
	pop	di
	pop	si
	pop	dx
	pop	cx
	pop	es
	pop	ds
	ret
GetDec	ENDP
	END