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 find the HCF of two numbers.

Algorithm

Start
Read count(C)
Read first number(A)
C <- C - 1
Read the next number(B)
Compare A and B
If A - B = 0 go to 13
If A - B < 0 go to 11
A <- A - B
go to 6
Swap A and B
go to 6
C <- C - 1
If CS != 1 go to 5
Store A
Stop

Flow Chart

Program

       LXI H, 2100H
       MOV C, M
       DCR C
       INX H
       MOV A, M
LOOP2: INX H
       MOV B, M
LOOP1: CMP B
       JZ NEXT
       JC EXG
       SUB B
       JMP LOOP1
EXG:   MOV C, B
       MOV B, A
       MOV A, C
       JMP LOOP1
NEXT:  DCR C
       JNZ LOOP2
       INX H
       MOV M, A
       RST-5

Example

2100H: 04
2101H: 06
2102H: 08
2103H: 10
2104H: 12
2105H: 02  ->  output

Let us know in the comments if you are having any questions regarding this microprocessor program.

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