# 8085 program to find the element that appears once

Prerequisite – Find the element that appears once in an array where every other element appears twice

**Problem – **Given 11 numbers, write an assembly language program to find the element that appears once where 5 numbers appear twice and one element appears once.

**Examples:**

Input : [01H, 02H, 09H, 01H, 01H, 02H, 0AH, 01H, 09H, 03H, 03H] Output : 0AH Every number appears even number of times, except 0AH which appears only once.

**Algorithm:**

Use XOR.

XOR of all the elements will give the number that appears once. This is because XOR of a number with itself is 0 and XOR of a number with 0 is the number itself.

^ => XOR res = 01H ^ 02H ^ 09H ^ 01H ^ 01H ^ 02H ^ 0AH ^ 01H ^ 09H ^ 03H ^ 03H Since XOR is associative and commutative : res = 0AH ^ (01H ^ 01H) ^ (01H ^ 01H) ^ (02H ^ 02H) ^ (03H ^ 03H) ^ (09H ^ 09H) = 0AH ^ 0 ^ 0 ^ 0 ^ 0 ^ 0 = 0AH ^ 0 = 0AH

**Steps:**

- Load the address of the first number in the HL register pair
- Initialize the register C with 0BH because we have to traverse 11 elements. It acts as a counter
- Initialize the accumulator with 0
- Take XOR of the value present at the address stored in the HL register with the accumulator and increment the address in the HL register
- Repeat step 4 for the rest of the 10 elements
- Store the value of the accumulator in 201DH (arbitrary)

201DH contains the answer.

ADDRESS | LABEL | MNEMONIC |
---|---|---|

2000H | LXI H, 2012H | |

2001H | ||

2002H | ||

2003H | MVI A, 00H | |

2004H | ||

2005H | MVI C, 0BH | |

2006H | ||

2007H | LOOP | MOV B, M |

2008H | XRA B | |

2009H | INX H | |

200AH | DCR C | |

200BH | JNZ LOOP | |

200CH | ||

200DH | ||

200EH | STA 201DH | |

200FH | ||

2010H | ||

2011H | HLT |

## Recommended Posts:

- 8085 program to find the set bit of accumulator
- 8085 program to find the sum of a series
- 8085 program to find larger of two 8 bit numbers
- 8085 program to find nth power of a number
- 8085 program to find 1's and 2's complement of 8-bit number
- 8085 program to find maximum of two 8 bit numbers
- 8085 program to find 1’s and 2’s complement of 16-bit number
- 8085 program to find the sum of series of even numbers
- 8085 program to find the sum of first n natural numbers
- 8085 program to find square of a 8 bit number
- 8085 program to find sum of digits of 8 bit number
- 8085 program to find the factorial of a number
- 8085 program to find smallest number between two numbers
- 8085 program to find minimum value of digit in the 8 bit number
- 8085 program to find maximum and minimum of 10 numbers

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.