8085 program to check whether both the nibbles of 8 bit number are equal or not

Problem – Write an assembly language program in 8085 microprocessor to check whether both the nibbles of 8 bit number are equal or not. If nibbles are equal then store 00 in memory location 3050 otherwise store FF in memory location 3050.

Example –

Assumption – Number, to check for similar nibbles is stored at memory location 2050.

Algorithm –



  1. Load the content of memory location 2050 in A.
  2. Moves the content of A in B.
  3. Mask the lower nibble and store it in register C.
  4. Move the content of B in A.
  5. Mask the higher order nibble and store it in A.
  6. Reverse the content of A by using RLC instruction 4 times.
  7. Compare the contents of A and C by help of CMP instruction. Update the flags of 8085.
  8. Now store FF if ZF = 0 otherwise store 00 if ZF = 1.
  9. Store the final result in memory location 3050.

Program –

MEMORY ADDRESS MNEMONICS COMMENT
2000 LDA 2050 A <- M[2050]
2003 MOV B, A B <- A
2004 ANI 0F A <- A (AND) 0F
2006 MOV C, A C <- A
2007 MOV A, B A <- B
2008 ANI F0 A <- A (AND) 0F
200A RLC Rotate content of A left by one bit without carry
200B RLC Rotate content of A left by one bit without carry
200C RLC Rotate content of A left by one bit without carry
200D RLC Rotate content of A left by one bit without carry
200E CMP C A – C
200F JZ 2018 Jump if ZF = 1
2013 MVI A, FF A <- FF
2015 JMP 201A Jump to memory location 201A
2018 MVI A, 00 A <- 00
201A STA 3050 M[3050] <- A
201D HLT END

Explanation – Registers A, B, C are used for general purpose.

  1. LDA 2050: load the content of memory location 2050 in accumulator A.
  2. MOV B, A: moves the content of A in register B.
  3. ANI 0F: performs AND operation in contents of A and 0F. Store the result in A.
  4. MOV C, A: moves the content of A in register C.
  5. MOV A, B: moves the content of B in A.
  6. ANI F0: performs AND operation in contents of A and F0. Store the result in A.
  7. RLC: rotates content of A left by one bit without carry. Use the instruction 4 times to reverse the number.
  8. CMP C: compares the content of A and C. Update the flags of 8085 accordingly.
  9. JZ 2018: jump to memory location 2018 if zero flag is set.
  10. MVI A, FF: assign FF to A.
  11. JMP 201A: jump to memory location 201A.
  12. MVI A, 00: assign 00 to A.
  13. STA 3050: store the content of A in memory location 3050.
  14. HLT: stops executing the program and halts any further execution.

Attention reader! Don’t stop learning now. Get hold of all the important CS Theory concepts for SDE interviews with the CS Theory Course at a student-friendly price and become industry ready.

My Personal Notes arrow_drop_up

Recommended Posts:

AmishTandon
Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.