8085 program to add two 16 bit numbers

In this program we will see how to add two 16-bit numbers.

Problem Statement

Write8085 Assembly language program to add two 16-bit number stored in memory location 8000H – 8001H and 8002H – 8003H.

Discussion

In this program we are pointing the operand addresses using HL and DE register pair. Then adding LSBytes by ADD operator, and after that adding MSBytes using ADC operator to consider the carry flag result. The 16-bit result will be stored at BC register, and by checking the carry bit after addition we can simply put 1 into memory.

We are taking two numbersBCAD + FE2D = 1BADA

Input

Address	Data
...	...
8000	AD
8001	BC
8002	2D
8003	FE
...	...

Flow Diagram

Program

Address	HEX Codes	Labels	Mnemonics	Comments
F000	21, 00, 80		LXI H,8000H	Point to LSB of first operand
F003	11, 02, 80		LXI D,8002H	Point to LSB of second address
F006	1A		LDAX D	Load Acc with content pointed by DE
F007	86		ADD M	Add memory element pointed by HL with Acc
F008	4F		MOV C, A	Store LSB result at C
F009	23		INX H	Point to next byte of first operand
F00A	13		INX D	Point to next byte of second operand
F00B	1A		LDAX D	Load Acc with content pointed by DE
F00C	8E		ADC M	Add memory element pointed by HL with Acc+ Carry
F00D	47		MOV B,A	Store the MSB at B
F00E	60		MOV H,B	Move B to H
F00F	69		MOV L,C	Move C to L
F010	22, 50, 80		SHLD 8050H	Store the result at 8050H and 8051H
F013	D2, 1B, F0		JNC DONE	Skip to end
F016	3E, 01		MVI A, 01H	Load 1 to Acc
F018	32, 52, 80		STA 8052H	Store Acc content into 8052H
F01B	76	DONE	HLT	Terminate the program