8085 program to determine if the number is prime or not

In this program we will see how to check a number is prime or not using 8085.

Problem Statement

Write 8085 Assembly language program to check whether a given number is prime or not.

Discussion

Here the approach is little bit different. We are actually counting the number of unique factors. For prime numbers the factors are only two. The 1 and the number itself. So if the result is 02H, then it is prime, otherwise not a prime number. As there is no division operation, we have to perform division by subtracting repeatedly.

Input

Address	Data
F100	07

Address	Data
F100	FF

Address	Data
F100	2F

Flow Diagram

Program

Address	HEX Codes	Labels	Mnemonics	Comments
F000	21, 00, F1		LXI H,F100	Point to F100 to take the number
F003	FE		MOV A,M	Take the number into Accumulator
F004	0E		MVI C,00	Clear C register
F006	57		MOV D,A	Copy A to D
F007	5F		MOV E,A	Copy A to E
F008	42	L2	MOV B,D	Load B with D
F009	B8	L1	CMP B	Compare B with A
F00A	DA, 11, F0		JC LABEL	if carry is generated, jump to Label
F00D	90		SUB B	Subtract B from A
F00E	C2, 09, F0		JNZ L1	Jump to L1
F011	FE, 00	LABEL	CPI 00	Compare A with 00H
F013	C2, 17, F0		JNZ SKIP	If Z = 0, jump to SKIP
F016	0C		INR C	Increase C by 1
F017	7B	SKIP	MOV A,E	Load A with E again
F018	15		DCR D	Decrease D by 1
F019	C2, 08, F0		JNZ L2	Jump to L2 label if Z = 0
F01C	79		MOV A,C	Load C to A
F01D	32, 01, F1		STA F101	Store result into F101
F020	76		HLT	Terminate the program