The program prompts the user to input a number and tells whether the input number is Prime or Not. The program can take a multidigit number as input.

The basic logic in the program is that after taking the number from the user, the program starts iteration from 2 to Number-1 and divide the number with every new value. If the remainder becomes 0 at any division it means that the number is not prime otherwise the number is prime.

 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 .MODEL SMALL .STACK 100H .DATA MSG DB "ENTER A NUMBER: \$" PRIMEMSG DB 0DH, 0AH, "NUMBER IS PRIME \$" NOTPRIMEMSG DB 0DH, 0AH, "NUMBER IS NOT PRIME \$" TOTAL DB 0 VALUE DB 0 .CODE MAIN PROC MOV AX, @DATA MOV DS, AX MOV AH, 9 LEA DX, MSG INT 21H READ: MOV AH, 1 INT 21H CMP AL, 13 JE ENDOFNUMBER MOV VALUE, AL SUB VALUE, 48 MOV AL, TOTAL MOV BL, 10 MUL BL ADD AL, VALUE MOV TOTAL, AL JMP READ ENDOFNUMBER: MOV AH, 0 MOV AL, TOTAL MOV BL, 2 CHECK: CMP AL, BL JE PRIME DIV BL CMP AH, 0 JE NOTPRIME INC BL MOV AL, TOTAL MOV AH, 0 JMP CHECK PRIME: MOV AH, 9 LEA DX, PRIMEMSG INT 21H JMP EXIT NOTPRIME: MOV AH, 9 LEA DX, NOTPRIMEMSG INT 21H EXIT: MAIN ENDP