8085 program to find 1’s and 2’s complement of 8-bit number

Problem – Write a program to find 1’s and 2’s complement of 8-bit number where starting address is 2000 and the number is stored at 3000 memory address and store result into 3001 and 3002 memory address. Example – Algorithm –

1. Load the data from memory 3000 into A (accumulator)
2. Complement content of accumulator
3. Store content of accumulator in memory 3001 (1’s complement)
4. Add 01 to Accumulator content
5. Store content of accumulator in memory 3002 (2’s complement)
6. Stop

Program –

Memory	Mnemonics	Operands	Comment
2000	LDA	[3000]	[A] <- [3000]
2003	CMA		[A] <- [A^]
2004	STA	[3001]	1’s complement
2007	ADI	01	[A] <- [A] + 01
2009	STA	[3002]	2’s complement
200C	HLT		Stop

Explanation –

1. A is an 8-bit accumulator which is used to load and store the data directly
2. LDA is used to load accumulator direct using 16-bit address (3 Byte instruction)
3. CMA is used to complement content of accumulator (1 Byte instruction)
4. STA is used to store accumulator direct using 16-bit address (3 Byte instruction)
5. ADI is used to add data into accumulator immediately (2 Byte instruction)
6. HLT is used to halt the program

Advantages of using 1’s and 2’s complement:

• They are widely used in digital circuits and computer architecture to represent negative numbers.
  
• They are simple and efficient methods for representing negative numbers and performing arithmetic operations on them.
  
• They require no extra hardware or memory to perform the negation operation, unlike other methods such as sign and magnitude.
  

Disadvantages of using 1’s and 2’s complement:

• The 1’s complement has two representations for zero (+0 and -0), which can lead to confusion and errors.
  
• The 2’s complement method requires an extra step of adding 1 to the 1’s complement, which may cause overflow errors if the number of bits used is not sufficient.
  
• The use of 1’s and 2’s complement can make certain operations more complex, such as division and comparison of signed numbers.