While modern high-level languages like C++ abstract away many low-level operations, sometimes it’s useful to get closer to the hardware to understand how things work under the hood. This example demonstrates how to subtract two 8-bit numbers using inline assembly in a simple C++ program.
#include<iostream.h>
#include<conio.h>
#include<stdio.h>
void main() {
clrscr();
short int a, b, c;
cout << "Enter First Number:";
cin >> a;
cout << "Enter Second Number:";
cin >> b;
asm mov ax, a // Move 'a' into AX
asm mov ah, 00h // Ensure AH is cleared
asm mov bx, b // Move 'b' into BX
asm mov bh, 00h // Ensure BH is cleared
asm sub al, bl // Subtract BL from AL
asm mov c, ax // Store result in 'c'
cout << "Result:";
cout << c;
getch();
}
This program demonstrates how to compare two integers using 8086 inline assembly in C++. By leveraging assembly instructions like sub and conditional jump js, the program determines which number is greater.
#include<iostream.h>
#include<conio.h>
void main() {
clrscr();
short a;
short b;
cout << "\n Enter First Number:";
cin >> a;
cout << "\n Enter Second Number:";
cin >> b;
asm mov ax, 0000h // Clear AX
asm mov bx, 0000h // Clear BX
asm mov ax, a // Load first number into AX
asm mov bx, b // Load second number into BX
asm sub ax, bx // Subtract BX from AX
asm js true // Jump if result is negative (AX < BX)
cout << "\n " << a << " is greater than " << b;
asm jmp end // Skip 'true' block
true:
cout << "\n " << b << " is greater than " << a;
end:
getch();
}
This C++ program calculates the factorial of a number between 0 and 8 using inline 8086 assembly instructions. The multiplication is handled within an assembly loop, showcasing a basic yet insightful use of mul, dec, and jnz instructions.
#include<iostream.h>
#include<conio.h>
void main() {
clrscr();
short a;
unsigned int c;
cout << "\n Enter Number between 0 to 8:";
cin >> a;
asm mov ax, 0000h
asm mov al, 01h // Initialize AX to 1
asm mov cx, 0000h
asm mov cx, a // Set CX loop counter to input value
bac:
asm mul cx // Multiply AX by CX
asm dec cx // Decrement CX
asm jnz bac // Loop until CX reaches zero
asm mov c, ax // Move result from AX to variable c
cout << "\n Factorial of " << a << " is " << c;
getch();
}
