How to check prime number using assembly language program

What is a Prime number?
A prime number is a natural number it has no positive divisor other than 1 and itself.

Prime number checking program is a beginner program for any programming language. In 8086 assembly language, checking prime number is an interesting logic.

Here is the microprocessor 8086 assembly language program to check whether the given number is prime or not.

It is a common program for beginners who wish to study basic programming steps in assembly language for 8086 microprocessor.

Read Also: Stepper Motor Interfacing with 8086

Logic of Prime Number Check in Assembly Code

Before going to the assembly code let me explain the programming logic first.

Suppose the given number is 'x'. Let us divide the number x with (x-1). I.e. x/(x-1).

Now check the reminder status. Reminder is store in DX register b default.

Now divide x with x-2, i.e. x/(x-2) then check the reminder.

Repeat this step up to the denominator become 2.

Denominator is like (x-1), (x-2),(x-3),....etc. 2

When the reminder=0, the number is 'Not Prime', else it is 'Prime'

Prime Number Program in 8086

Now let’s see the 8086 assembly language code for prime number checking.

1000  XOR CX,CX      /*Clearing the registers*/
1002  XOR DX,DX      /*Clearing the registers*/
1004  MOV AX,[1500]  /*Assume the number is store in memory 1500*/
1006  MOV BX,AX      /*Copy the value in AX to BX */
1008  DEC BX
1010  DIV BX         /*Dividing*/
1012  CMP DX,0000    /*Check for Reminder, Reminder is stored in DX*/
1014  JZ step 13
1016  XOR DX,DX      /*Clearing DX*/
1018  CMP BX,0002
1020  JNZ 1008
1022  MOV CX,0001
1024  MOV [2000],CX  /*Storing the result*/
1026  HLT

If you have any doubts regarding to the above described assembly language program feel free to ask using the comment box below. Keep visiting CircuitsGallery for more about 8086.
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