8085 is a Microprocessor which was developed by Intel in 1970s. All the instructions in this microprocessor are encoded in a single byte. Some of the instructions are followed by one or two bytes of data, which can be a memory address, an immediate operand or a port number.

In this post, we will write a program in 8085 to multiply two 8-bit numbers without using shifting multiplicand.

Algorithm

Start
Read multiplier
Read multiplicand
Extend multiplicand to double(16-bit)
prod <- 0
count <- 8
Left shift product
Left shift multiplier
If CS != 1 go to 11
prod <- prod + multiplicand
count <- count - 1
If count != 0 go to 7
Store prod
Stop

Flow Chart

Program

      LHLD 2100H
      MOV A, L
      MOV E, H
      MVI D, 00H
      LXI H, 0000H
      MVI C, 08H
BACK: DAD H
      RAL
      JNC NEXT
      DAD D
NEXT: DCR C
      JNZ BACK
      SHLD 2102H
      RST-5

Example

2100H: 02
2101H: 03
2102H: 06  ->  Output

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