2's Complement of 2Byte Number

This program will work out the 2's Complement of a 2 Byte Number. As Microprocessor can perform 8 bits at a time in Accumulator, so we follow the foloowing Algo Fetch the 2 Byte Number in a Register Pair Bring Least Significant Byte of the Number from last Register into A (Accumulator) Make Complement of A and add 1 Store back the Updated LSByte into its source Register Bring MSByte of the Number from another Register into A Make Complement of A and add 1 if carry was genetrated at the time of LSByte opeartion Store back the Updated MSByte into its source Register Store the Result to a Memory location Suppose, Argument Number is stored in Location 1000H and 1001H Memory Location and store the value in 2000H and 2001H Memory Locations.
Memory Location	Hex Code	Label	Mnemonics	Comment
3050 3051 3052	2A 00 10	START:	LHLD 1000H	;Load the HL Register Pair with the content of Memory Location 1000H and 1001H
3053	7D		MOV A, L	;Move the Content of L to A (Accumulator)
3054	2F		CMA	;Make Complement of Least Significant Byte of the Number
3055 3056	C6> 01		ADI 01H	;Add 1 with LSByte of the number to make 2's complement
3057	6F		MOV L, A	;Send Back the Updated Data to L
3058	7C		MOV A, H	;Bring the MSByte of the Number in A
3059	2F		CMA	;Make 1's Complement of MSByte of Number
305A 305B 305C	D2 5F 30		JNC NOCARRY	;If Carry was not generated in LSByte Operation, Jump into NOCARY Section
305D 305E	C6 01		ADI 01H	;Make 2's Complement of MSByte if carry was generated in LSByte operation
305F	67	NOCARRY:	MOV H, A	;Send back the Updated MSByte to H
3060 3061 3062	22 00 20		SHLD 2000H	;Store the Result from HL to the Memory Location 2000H
3063	76		HLT	;End of Program

If you want to use INR A to add 1 with 1's Complement to make 2's Complement, you should use at the time of increamention of MSByte not at LSByte. Because INR do not update CY(Carry) Flag if carry is generated.

You can use the following algo also to do the same.

1. Fetch the 2 Byte Number in a Register Pair
2. Bring the Least Significant Byte into A
3. Make Complement of A
4. Store back to Register
5. Bring the MSByte into A
6. Make Complement of A
7. Store Back to Register
8. increase this Resgister pair using INX Rp
9. Store the Result in Memory