This post walks through a C++ program that demonstrates how to perform basic arithmetic operations like multiplication and division using inline assembly. It allows the user to choose between signed/unsigned multiplication and division in a loop until they decide to exit.
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(); }