8085 program to find the sum of first n natural numbers

In this program we will see how to add first n natural numbers.

Problem Statement

Write 8085 Assembly language program to add first N natural numbers. The value of N is provided.

Discussion

We are getting the value of N from memory location 8000H. We are using the number N as count variable, in each step we are calculating (A + Count) value, and store them into A. After adding them, the count value is decreased,thus the total series is completed.

If the number is 23H(35D), then the sum will be (35*36)/2 = 630 (276H)

Input

Address	Data
. . .	. . .
8000	23
. . .	. . .

Flow Diagram

Program

Address	HEX Codes	Labels	Mnemonics	Comments
F000	21, 00, 80		LXI H,8000H	Point to get the upper limit
F003	4E		MOV C, M	Load the upper limit to C
F004	AF		XRA A	Clear the A register
F005	47		MOV B, A	Also clear B register
F006	81	LOOP	ADD C	Add C with A
F007	D2, 0B, F0		JNC SKIP	If CY = 0,Skip next step
F00A	04		INR B	Increase B ifCY = 1
F00B	0D	SKIP	DCR C	Decrease C by1
F00C	C2, 06, F0		JNZ LOOP	Until Z = 1,go to LOOP
F00F	21, 50, 80		LXI H, 8050H	Point to the destination address
F012	77		MOV M, A	Store the acc content
F013	23		INX H	Point to next location
F014	70		MOV M, B	Store the MSbyte
F015	76		HLT	Terminate the program