Inline assembly in MSVC

main.cpp

#include <stdio.h>

extern "C" int __stdcall my_proc(int, int);

int main(void)
{ 
  int a = 1, b = 0, c = 2;   

	// calculate b = c^2 - a
    __asm 
	{
		mov eax, c   ; eax = c
		mul eax      ; eax = eax * eax = c ^ 2
		mov ebx, a   ; ebx = a
		sub eax, ebx ; eax = eax - ebx = c ^ 2 - a
		mov b, eax   ; b = eax
	}

	printf("b = (%d ^ 2) - %d = %d\n", c, a, b);

    // call b = my_proc(c, a)
    b = my_proc(c, a);

    printf("called my_proc(%d, %d) = %d\n", c, a, b);
	
	return 0;
}

my_proc.asm

.686
.model flat, stdcall

.code
my_proc proc   public, c1:DWORD, a1:DWORD

      mov   eax, c1
      add   ebx, a1
      mul   eax
      
      sub   eax, ebx 

      ret                   
my_proc endp
end

output

b = (2 ^ 2) - 1 = 3
called my_proc(2, 1) = 2