BCD.DOC -- Description of BCD.ASM
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  From `BLUEBOOK of ASSEMBLY ROUTINES for the IBM PC & XT'
        by Christopher L. Morgan
        Copyright (C) 1984 by The Waite Group, Inc.

  Purpose:  BCD.ASM contains routines to convert between internal binary
    coded decimal (BCD) and other formats, both internal and external.
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   Contents:
   ---------
   BCDIN	--  Convert from ASCII Decimal to BCD
   BCDOUT	--  Convert from BCD to ASCII Decimal
   BCD2I16	--  Convert from BCD to 16-bit Binary
   I162BCD	--  Convert from 16-bit Binary to BCD
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  Overview:
	These routines can convert external decimal representation and 
  internal BCD representation, and between internal binary and internal BCD.
	The internal BCD format packs two decimal digits per byte, one per
  nibble.  By using a large number of bytes, you can precisely represent
  high precision decimal numbers.  These routines use 18 bytes of storage to 
  handle 36-digit BCD numbers, but are easily modified to handle other sizes.
	Fixed point numbers can be handled by assigning a fixed position for
  a decimal point.  For example, dollars & cents can be handled by assigning
  the decimal point so there are exactly two BCD digits to its right, which
  form the fractional part of the number.
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BCDIN

  Function: This routine accepts a decimal number from the standard input
    device and converts it to internal BCD format.

  Input: The individual digits of the decimal number are received in ASCII
    through a call to a standard I/O routine. The valid digits are 0 
    through 9. An ASCII code other than a digit will terminate the routine.

  Output: On return a 36-digit number is stored in BCD form in an
    18-byte buffer called BCDBUFF.

  Registers used: No registers are modified.

  Segments referenced: DATAS is data segment which contains BCDBUFF.

  Routines called: STDIN
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BCDOUT

  Function: This routine converts a 36-digit number stored in BCD form to
    ASCII decimal form which is sent to the standard output device.

  Input: Upon entry a 36-digit number is stored in an 18-byte BCD buffer
    called BCDBUFF.

  Output: A string of ASCII digits representing a decimal number is stored
    in a buffer called TBUFF and then sent out through a standard I/O routine.

  Registers used: No registers are modified.

  Segments referenced: DATAS is a data segment containing BCDFUFF and TBUFF.

  Routines called: STDOUT
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BCD2IB16

  Function: This routine converts from internal BCD to intermal binary format.

  Input: Upon entry a 36-digit number is contained in am 18-byte BCD buffer
    called BCDBUFF.

  Output: A 16-bit binary number is returned in the DX register.

  Registers used: Only DX is modified. DX is used for output.

  Segments referenced: DATAS is a data segment containing the buffer, BCDBUFF.
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IB162BCD

  Function: This routine converts internal 16-bit binary numbers to numbers
    stored in internal BCD format.

  Input: Upon entry a 16-bit binary number is in the DX register.

  Output: On return a 36-digit number is stored in BCD form in an 18-byte
    buffer called BCDBUFF.

  Registers used: No registers are modified. DX is used for input.

  Segments referenced: DATAS is a data segment containing BCDBUFF.
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