Contributor: UNKNOWN { Depending on the application, BCD may solve your problem. But if you really need a _large_ binary integer you are going to have to use multiple precision arithmetic. This is relatively easy to do in assembler and just a little more difficult in a high-level language. You need to define your _integer_ as an array of 256 bytes, 128 words, or 64 unsigned long integers. So we're stuck with words. So our bigint is an array[0..127] of word; We'll do it little-endian 0=least significant word, 127 = most significant word. Using words with a longint intermediate value actually makes our task a little easier. } CONST MaxBIG = 127; TYPE tBigInt = Array[0..MaxBIG] of Word; PROCEDURE BigAdd(VAR Op1, Op2: tBigInt); { --------------------------------------------- } { Do multiprecision add: Op1 := Op1 + Op2 } { --------------------------------------------- } VAR i: Integer; Temp: Longint; Begin Temp := 0; { Clear carry } For i := 0 to MaxBIG Do Begin Temp := Longint(Op1[i]) + Op2[i] + Temp; Op1[i] := Word(Temp); Temp := Temp shr 16; { Carry = High word } End; END; PROCEDURE BigSub(VAR Op1, Op2: tBigInt); { --------------------------------------------- } { Do multiprecision Substract: Op1 := Op1 - Op2 } { --------------------------------------------- } VAR i: Integer; Temp: Longint; Begin Temp := 0; { Clear carry } For i := 0 to MaxBIG Do Begin Temp := Longint(Op1[i]) - Op2[i] - Temp; Op1[i] := Word(Temp); Temp := Temp shr 16; { Carry = High word } End; END; I've done the easy part. It's your turn to put together the multiprecision multiply and divide. If Op2 can be an integer I'll toss together an op1*Op2 and Op1 div Op2. But for a full version I'd have to crack the books :-)