Program to Subtract two 8-bit numbers without borrow

Q. Write an 8085 program and draw a flowchart to Subtract two 8-bit numbers without considering the borrow.(8085 Microprocessor Program)



Address Mnemonics Operand Opcode Comments
2000 LXI H, 3000H 21 Load H-L pair with address 3000H.
2001 00
2002 30
2003 MOV A, M 7E Move the 1st operand from memory to reg. A.
2004 INX H 23 Increment H-L pair.
2005 MOV B, M 46 Move the 2nd operand from memory to reg. B.
2006 SUB B 90 Subtract B from A.
2007 INX H 23 Increment H-L pair.
2008 MOV M, A 77 Move the result from reg. A to memory.
2009 HLT 76 Halt


Before Execution:

3000H: 05H
3001H: 02H

After Execution:

3002H: 03H

Program Explanation

  1. This program subtracts two operands stored in memory location 3000H and 3001H, without considering the borrow taken (if any).
  2. Let us assume that the operands stored at memory location 3000H is 05H and 3001H is 02H.
  3. Initially, H-L pair is loaded with the address of first memory location.
  4. The first operand is moved to accumulator from memory location 3000H and H-L pair is incremented to point to next memory location.
  5. The second operand is moved to register B from memory location 3001H.
  6. The two operands are subtracted and the result is stored in the accumulator.
  7. H-L pair is again incremented and the result is moved from the accumulator to memory location 3002H.

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