8086 program to divide a 16 bit number by an 8 bit number

Problem – Write an assembly language program in 8086 microprocessor to divide a 16 bit number by an 8 bit number.

Example –

Algorithm –

1. Assign value 500 in SI and 600 in DI
2. Move the contents of [SI] in BL and increment SI by 1
3. Move the contents of [SI] and [SI + 1] in AX
4. Use DIV instruction to divide AX by BL
5. Move the contents of AX in [DI].
6. Halt the program.

Assumption – Initial value of each segment register is 00000.

Calculation of physical memory address –
Memory Address = Segment Register * 10(H) + offset,
where Segment Register and Offset is decided on the basis of following table.

OPERATIONS	SEGMENT REGISTER	OFFSET
Instruction fetching	Code Segment	Instruction Pointer
Data operation	Data Segment	Base Register [BX], Displacement [DISP]
Stack operation	Stack Segment	Stack Pointer (SP), Base Pointer (BP)
String as a source	Data Segment	Source Indexed (SI)
String as a destination	Extra Segment	Destination Indexed (DI)

Program –

MEMORY ADDRESS	MNEMONICS	COMMENT
0400	MOV SI, 500	SI <- 500
0403	MOV DI, 600	DI <- 600
0406	MOV BL, [SI]	BL <- [SI]
0408	INC SI	SI <- SI + 1
0409	MOV AX, [SI]	AX <- [SI]
040B	DIV BL	AX <- AX / BL
040D	MOV [DI], AX	[DI] <- AX
040F	HLT	End of program

Explanation – Registers used AX, BL, SI, DI

1. MOV SI, 500 assigns 500 to SI
2. MOV DI, 600 assigns 600 to DI
3. MOV BL, [SI] moves the content of [SI] to BL register i.e. value of divisor will be stored in BL
4. INC SI increment the content of SI by 1
5. MOV AX, [SI] moves the content of [SI] and [SI + 1] to AX register i.e. value of dividend will be stored in AX
6. DIV BL divide the content of AX by BL, after execution of this instruction the quotient get stored in AL and remainder in AH
7. MOV [DI], AX moves the content of AX to [DI]
8. HLT stops executing the program and halts any further execution