8085 program to find the factorial of a number

In this program we will see how to find the factorial of a number.

Problem Statement

Write 8085 Assembly language program to find the factorial of an 8-bit number.

Discussion

In 8085, there is no direct instruction to perform multiplication. We need to perform repetitive addition to get the result of the multiplication. In each step we are decreasing the value of B and multiply with the previous value of B. We are repeating these steps until B reaches 1. and B – 1 to 0. Thus the factorial is generated.

Input

Address	Data
8000	05

Flow Diagram

 

Program

Address	HEX Codes	Labels	Mnemonics	Comments
F000	21, 00, 80		LXI H, 8000H	Load the number
F003	46		MOV B,M	Take number from memory to B
F004	16, 01		MVI D, 01H	Set D to 01H
F006	CD, 10, F0	FACT	CALL MUL	Call multiplication
F009	05		DCR B	Decrease B by 1
F00A	C2, 06, F0		JNZ FACT	If Z = 0, jump to Fact
F00D	23		INX H	Point to next location
F00E	72		MOV M,D	Store result in memory
F00F	76		HLT	Terminate the program
F010	58	MUL	MOV E,B	Load B to E
F011	AF		XRA A	Clear accumulator to store result
F012	82	ML	ADD D	Add D to A
F013	1D		DCR E	Decrement E
F014	C2, 12, F0		JNZ ML	If Z = 0, jump to ML
F017	57		MOV D,A	Transfer contents of A to D
F018	C9		RET	Return result

Output

Address	Data
8001	78