# 8085 program to reverse 16 bit number

Problem – Write an assembly language program in 8085 microprocessor to reverse 16 bit number.

Example – Assume 16 bit number is stored at memory location 2050 and 2051.

Algorithm –

1. Load contents of memory location 2050 in register L and contents of memory location 2051 in register H
2. Move contents of L in accumulator A
3. Reverse the contents of A by executing RLC instruction 4 times
4. Move the contents of A in L
5. Move the contents of H in A
6. Reverse the contents of A by executing RLC instruction 4 times
7. Move the contents of L in H
8. Move the contents of A in L
9. Store the content of L in memory location 2050 and contents of H in memory location 2051

Program –

2000 LHLD 2050 L <- M[2050], H <- M[2051]
2003 MOV A, L A <- L
2004 RLC Rotate accumulator content left by 1 bit without carry
2005 RLC Rotate accumulator content left by 1 bit without carry
2006 RLC Rotate accumulator content left by 1 bit without carry
2007 RLC Rotate accumulator content left by 1 bit without carry
2008 MOV L, A L <- A
2009 MOV A, H A <- H
200A RLC Rotate accumulator content left by 1 bit without carry
200B RLC Rotate accumulator content left by 1 bit without carry
200C RLC Rotate accumulator content left by 1 bit without carry
200D RLC Rotate accumulator content left by 1 bit without carry
200E MOV H, L H <- L
200F MOV L, A L <- A
2010 SHLD 2050 M[2050] <- L, M[2051] <- H
2013 HLT END

Explanation – Registers A, H, L are used for general purpose.

1. LHLD 2050: loads contents of memory location 2050 in L and 2051 in H.
2. MOV A, L: moves content of L in A.
3. RLC: shift the content of A left by one bit without carry. Repeat the current instruction 4 times so that contents of A get reversed.
4. MOV L, A: moves the content of A in L.
5. MOV A, H: moves the content of H in A.
6. RLC: shift the content of A left by one bit without carry. Repeat the current instruction 4 times so that contents of A get reversed.
7. MOV H, L: moves the content of L in H.
8. MOV L, A: moves the content of A in L.
9. SHLD 2050: stores the content of L in 2050 and H in 2051.
10. 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

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.