Implementing Assembly Language Program for Counting Prime Numbers in an Array: An EMU 8086 Example

Introduction

As a developer working with low-level systems such as the EMU 8086 emulator, writing efficient and accurate algorithms is crucial for optimizing performance and achieving desired functionalities. One common task involves processing arrays to find prime numbers. In this guide, we will explore how to write an assembly language program for the EMU 8086 emulator to count the number of prime numbers in a given array. This article will cover the necessary steps, provide a detailed example, and explain the code thoroughly.

Steps to Implement the Program

EMU 8086 Assembly Program to Count Prime Numbers in an Array

Data Section

.model      array db 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 ; Array of numbers    array_size db 10                          ; Size of the array    prime_count db 0                          ; Counter for prime numbers

Code Section

main:    mov ax, @data    mov ds, ax    mov cx, [array_size]                     ; Load array size into CX    lea si, array                            ; Load address of array into SI    xor bx, bx                               ; Clear BX prime counternext_number:    mov al, [si]                             ; Load the current number into AL    call is_prime                            ; Call is_prime function    cmp al, 1                                ; Check if the number is prime    jne not_prime                            ; If not prime, skip incrementing counter    inc bx                                   ; Increment prime counternot_prime:    inc si                                    ; Move to the next number in the array    loop next_number                         ; Loop until all numbers are checked    mov [prime_count], bl                    ; Store the prime count in prime_count    mov ax, 4C00h                            ; DOS interrupt to exit    int 21h

Function to Check If a Number in AL is Prime

is_prime:    cmp al, 2                                ; Check if number is less than 2    jl not_prime_return                      ; Numbers less than 2 are not prime    je prime_return                          ; 2 is prime    mov cl, 2                                ; Start checking from 2check_div:    mov dl, al                               ; Copy the number to DL    xor ah, ah                               ; Clear AH to use DX:AX for division    div cl                                   ; Divide AL by CL    cmp ah, 0                                ; Check if there was no remainder    je not_prime_return                      ; If remainder is 0, it's not prime    inc cl                                   ; Increment divisor    cmp cl, al                               ; Compare divisor with the number    jl check_div                             ; If divisor is less than the number, check againprime_return:    mov al, 1                                ; Set AL to 1 (True)    retnot_prime_return:    mov al, 0                                ; Set AL to 0 (False)    retend main

Explanation

The main procedure initializes the data segment and starts processing the array. It uses a loop to iterate through each element of the array, calling the is_prime function to check if the current number is prime. If a number is prime, it increments the prime_count.

The is_prime function checks if the number in AL is prime. It handles special cases for numbers less than 2 and divides the number by all integers starting from 2 up to the number itself to check for factors. If it finds a factor, it returns 0 (not prime); otherwise, it returns 1 (prime).

Guidelines

Make sure to run this code in an environment that supports EMU 8086 assembly language. Feel free to adjust the array values and size as needed for your specific use case.