Program to find 2’s complement of an 8-bit number

Q. Write an 8085 program and draw a flow chart to find 2’s complement of an 8-bit number.(8085 Microprocessor Program)

Flowchart/Algorithm

Program

Address	Mnemonics	Operand	Opcode	Comments
2000	LDA	3000H	3A	Load H-L pair with data from 3000H.
2001			00
2002			30
2003	CMA		2F	Complement accumulator.
2004	INR	A	2C	Increment accumulator.
2005	STA	3001H	32	Store the result at memory location 3001H.
2006			01
2007			30
2008	HLT		76	Halt

Output

Before Execution:

3000H: 85H

After Execution:

3001H: 7BH

Program Explanation

This program finds the 2’s complement of an 8-bit number stored in memory location 3000H.
Let us assume that the operand stored at memory location 3000H is 85H.
The operand is moved to accumulator from memory location 3000H.
Then, its complement is found by using CMA instruction.
One is added to accumulator by incrementing it to find its 2’s complement.
The result is stored at memory location 3001H.