8085 program to find square root of a number

Now let us see a program of Intel 8085 Microprocessor. This program will find the square root of a number.

Problem Statement

Write an assembly language program to find the square root of a number in L and store the result at location 8100H

Discussion

Here we are using division method for finding square root of a number. As we know there is no division operation in 8085, so we are creating division subroutine.

Let N is the number.

X = √N

X² = N

X² + X² = N + X²

2X² = N + X²

X² = (N + X²)/2

X =((N + X²)/X)/2

X_New=(N / X + X)/2

If X = X_New then X = √N

Input

We have tested with three inputs: These inputs are −

64H (100D)
51H (81D)
90H (144D)

Flow Diagram

Program

Address	HEX Codes	Labels	Mnemonics	Comments
8000	80, 00, 83	START	LXI SP, 8300H	SP = 8300H
8003	3E, 01		MVI A, 01H	A (first approximation) = 01 H
8005	57	UP	MOV D, A	D = A Tracking Xold
8006	2E, NUM		MVI L, NUM	L = number N whose square root is to be calculated
8008	CD, 1E, 80		CALL DIV	Call div subroutine to calculate N/X HereN in L and X in A. It performs L = L/A and it returns result in L
800B	7D		MOV A, L	A = L (return argument)
800C	82		ADD D	A = A+D (N/X) + X
800D	26, 00		MVI H, 00H	H = 00 H
800F	6F		MOV L, A	L = A
8010	3E, 02		MVI A, 02H	A = 02 H
8012	CD, 1E, 80		CALL DIV	Call div subroutine Here sum in L and 2in A Xnew= ((N/X_old)+ X_old)/2
8015	7D		MOV A, L	A = L
8016	BA		CMP D	Compare D and A Comparing X_old and X_new
8017	C2, 05, 80		JNZ UP	Is A = D, if no go to up If they are equal then the obtained value of X is the answer
801A	32, 00, 81		STA 8100H	Store the result at the desired memory location 8100H
801D	76		HLT	Stop
801E	4F	DIV	MOV C, A	C = A
801F	7D		MOV A, L	A = l
8020	2E, 00		MVI L, 00H	L = 00
8022	B9	UP1	CMP C	Compare a and c registers
8023	D8		RC	Is A < C? If yes return to main
8024	91		SUB C	A = A – C
8025	2C		INR L	L = L + 1
8026	C3, 22, 80		JMP UP1	Go back to UP1
8000	80, 00, 83	START	LXI SP, 8300H	SP = 8300H