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'BCD Library for MMBasic - V 1. 18 August 2014
'
'(c) Peter Carnegie 2014 with thanks to TassyJim from the BackShed
'who inspired this library with his BigInt Library, and JohnS who had
'the insight that integer operation on 6 digit numbers in MMBasic was
'viable without loss of precision.
'
'This library is NOT Re-entrant, eg should not be used within ISR's
'
'All Global/Externally visible symbols have the prefix BCD. , eg BCD.AddAB2C
'
'The BCD Library will operate on numbers from 12 Digits to 252 Digits
'
'BCD Library uses 6 arrays, BCD.A(), BCD.B(), BCD.C(),
' BCD._A(), BCD._B(), BCD._C()
'These arrays are treated as BCD registers capable
'of holding up to 252 decimal digit numbers.
'
'Numbers are stored in unpacked form, 6 decimal digits per
'array entry, in little endian form.
'eg 123456789 is stored in BCD.A() as
'BCD.A(0)=456789, BCD.A(1)=000123, BCD.A(2)=000000
'
'Algorithms process Sextets of digits at a time reducing
'processing times, eg on a uMite at 48MHz, an 18 digit BCD.AddAB2C
'operation takes about 4mS.
'
'Generally, register BCD.C() will contain the results of
'two part operations, eg BCD.AddAB2C takes BCD.A() + BCD.B()
'and returns the result in BCD.C().
'
'
'
'The list of functions/subs in the library include
'
' BCD.InitLib(NumDigits) MUST be called first. Creates Global BCD Lib Vars, BCD.A/B/C(), BCD.Size, BCD.Width, BCD.NumDigits
' NumDigits is Number of BCD digits, eg 24,
' BCD.Size will return number of elements used to represent NumDigits, ie NumDigits\BCD.Width
' BCD.Width will return number of digits per numeric var - always 6
' BCD.NumDigits will return number of BCD Digits, ie precision
'
' BCD.AddAB2C BCD.C()=BCD.A()+BCD.B()
' BCD.SubAB2C BCD.C()=BCD.A()-BCD.B()
' BCD.SubAB2A BCD.A()=BCD.A()-BCD.B()
' BCD.IncA(Inc) BCD.A()=BCD.A()+Inc Note Inc is a SINGLE
' BCD.DecA(Dec) BCD.A()=BCD.A()-Dec Note Dec is a SINGLE
' BCD.MulAB2C BCD.C()=BCD.A()*BCD.B()
' BCD.DivAB2C BCD.C()=BCD.A()\BCD.B()
'
'Utility Routines******************
'
' BCD.Clr(Dest,NumDigits) Dest(0..NumDigits-1)=0
'
' BCD.Load(Dest,A$,NumDigits) Load Dest BCD with VAL(A$),NumDigits is optional, if 0 then Numdigits will default to 7
'
' BCD.LPad$(A$,ML) Pad a string with leading zeroes to make a string ML chars long
'
' BCD.A2Bin BCD.C() = BCD to Binary conversion of BCD.A() in little endian format
' BCD.A2Asc$() Returns String representation of BCD.A()
'
' BCD.Print(Src,Mode,NumDigits) Print a BCD register to console,Src is first element of BCDregister, eg FREQ(0)
'
' BCD.Copy(Src,Dest,NumDigits) Copy a BCD number from source to dest, Src and Dest are first element opf BCD register, BCD.A(0)
'
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