Prerequisite – Bubble Sort
Problem – Write an assembly language program in 8085 microprocessor to sort a given list of n numbers using Bubble Sort.
Assumption – Size of list is stored at 2040H and list of numbers from 2041H onwards.
- Load size of list in C register and set D register to be 0
- Decrement C as for n elements n-1 comparisons occur
- Load the starting element of the list in Accumulator
- Compare Accumulator and next element
- If accumulator is less than next element jump to step 8
- Swap the two elements
- Set D register to 1
- Decrement C
- If C>0 take next element in Accumulator and go to point 4
- If D=0, this means in the iteration, no exchange takes place consequently we know that it won’t take place in further iterations so the loop in exited and program is stopped
- Jump to step 1 for further iterations
|2000H||START||LXI H, 2040H||Load size of array|
|2003H||MVI D, 00H||Clear D register to set up a flag|
|2005H||MOV C, M||Set C register with number of elements in list|
|2006H||DCR C||Decrement C|
|2007H||INX H||Increment memory to access list|
|2008H||CHECK||MOV A, M||Retrieve list element in Accumulator|
|2009H||INX H||Increment memory to access next element|
|200AH||CMP M||Compare Accumulator with next element|
|200BH||JC NEXTBYTE||If accumulator is less then jump to NEXTBYTE|
|200EH||MOV B, M||Swap the two elements|
|200FH||MOV M, A|
|2011H||MOV M, B|
|2013H||MVI D, 01H||If exchange occurs save 01 in D register|
|2015H||NEXTBYTE||DCR C||Decrement C for next iteration|
|2016H||JNZ CHECK||Jump to CHECK if C>0|
|2019H||MOV A, D||Transfer contents of D to Accumulator|
|201AH||CPI 01H||Compare accumulator contents with 01H|
|201CH||JZ START||Jump to START if D=01H|
- Retrive an element in accumulator.
- Compare it with next element, if it is greater then swap otherwise move to next index.
- If in one entire loop there has been no exchange, halt otherwise start the whole iteration again.
- The following approach has two loops, one nested inside other so-
Worst and Average Case Time Complexity: O(n*n). Worst case occurs when array is reverse sorted.
Best Case Time Complexity: O(n). Best case occurs when array is already sorted.