C or C++ code

I posted this code on another forum and was blasted because it is supposedly not C, but C++. Can someone please show me wherein this code is not legitimate C code? I dont' see it.

Code:

#include <stdio.h>
 
int main(unsigned char *argv[], int argc)
{
  //declare two integers and load them with unique values
  int x = 5;
  int y = 3;
  
  //report the pre-algorithm values to the user
  printf("before:\n");
  printf("x = %d\n", x);  
  printf("y = %d\n", y);
  
  //the 1st variable now holds the sum of both integers (x = 5 + 3 or x = 8)
  x = x + y;

  //the 2nd variable now holds the result of subtracting its original value from the sum
  //(y = 8 - 3 or y = 5)
  y = x - y;
  
   //the 1st variable now holds the result of subtracting its 2nd variable from the sum 
  //(x = 8 - 5 or x = 3) 
  x = x - y; 

 
 //report the post-algorithm values to the user
  printf("after:\n");  
  printf("x = %d\n", x);  
  printf("y = %d\n", y);

}

Thanks in advance.

It's C99, except the parameters of main are the wrong way around. It should be one of:

Code:

int main(int argc, char *argv[])
int main(void)

It would be valid C89 (more common) if:

(a) you removed the C99/C++ style // comments, or replaced them with /* */ comments.
(b) you added an explicit return 0; on the end of the main function.