8085 program for Binary search

Here we will see how to perform binary search in 8085.

Problem Statement:

Write 8085 Assembly language program to perform binary search on a set of data stored at location F110 to F119. The key is located at F100.

Discussion

To perform binary search, the array must be sorted. We are taking the lower limit into L and upper limit into H. The array location is stored at DE register pair. The mid is calculated using (H + L)/2. To perform this division, we are just shifting it to the right one time. Then put the mid value into D and check the item located using DE. if the number is same, then jump to end and store 1 at F101. This indicates that item is found, and also store the mid value as index. If the mid is not matched, then there are two case, if the number is smaller than the mid element, then it is in the lower half, so the upper limit will be mid – 1, in another case it will be in the other side, so the lower limit will be mid + 1. If the item is not found it will store 02 at location F101.

Input

Address	Data
F100	48
…	…
F110	04
F111	08
F112	22
F113	2B
F114	31
F115	38
F116	48
F117	51
F118	54
F119	62
…	…

Address	Data
F100	9D
…	…
F110	04
F111	08
F112	22
F113	2B
F114	31
F115	38
F116	48
F117	51
F118	54
F119	62
…	…

Flow Diagram

Program

Address	HEX Codes	Labels	Mnemonics	Comments
F000	3A, 00, F1		LDA F100	Load the key into A
F003	47		MOV B,A	Store key into B
F004	AF		XRA A	Clear Acc
F005	32, 03, F1		STA F103	Store number of iterations into F103H
F008	6F		MOV L,A	Store A into L also
F009	26, 09		MVI H,09	Load 9 into H
F00B	3A, 03, F1	START	LDA F103	load number of iterations into A
F00E	3C		INR A	Increase A
F00F	32, 03, F1		STA F103	Restore number of iterations
F012	7C		MOV A,H	Take the upper limit from H to A
F013	BD		CMP L	Compare A and L
F014	DA, 46, F0		JC L2	If CY = 1, jump to L2
F017	85		ADD L	Otherwise add L with A
F018	1F		RAR	Right rotate to get half of it
F019	4F		MOV C,A	Store mid value into C
F01A	D2, 1E, F0		JNC RESET	If CY = 0, jump to Reset
F01D	3F		CMC	Complement the carry
F01E	11, 10, F1	RESET	LXI D,F110	Load the initial address of array into DE
F021	83		ADD E	Add E and Mid
F022	5F		MOV E,A	Store index into E
F023	AF		XRA A	Clear A
F024	8A		ADC D	Add D with A with the carry
F025	57		MOV D,A	Restore A into D
F026	1A		LDAX D	Load A with the value of mid position
F027	B8		CMP B	compare it with Key
F028	DA, 34, F0		JC ELSE	If CY = 1, jump to ELSE
F02B	CA, 3A, F0		JZ PRINT	If they are same, jump to PRINT
F02E	79		MOV A,C	Take the mid from C to A
F02F	3D		DCR A	Decrease A to get mid – 1
F030	67		MOV H,A	Update the upper limit with mid – 1
F031	C3, 0B, F0		JMP START	Jump to START again
F034	79	ELSE	MOV A,C	Load the mid from C to A
F035	3C		INR A	increase A to get mid + 1
F036	7D		MOV A,L	update lower limit with mid + 1
F037	C3, 0B, F0		JMP START	Jump to START again
F03A	3E, 01	PRINT	MVI A,01	Load 1 as item is found
F03C	32, 01, F1		STA F101	Store result at F101
F03F	79		MOV A,C	Take the mid from C to A
F040	32, 02, F1		STA F102	Store index of the key into F102
F043	C3, 4B, F0		JMP END	End the task
F046	3E, 02	L2	MVI A,02	Load 2 into A that key not present
F048	32, 01, F1		STA F101	Store result at F102
F04B	76	END	HLT	Terminate the program

Output

Address	Data
F101	01
F102	06

Address	Data
F101	02

Chandu yadav

Updated on: 30-Jul-2019

1K+ Views

Kickstart Your Career

Get certified by completing the course

Get Started