C / C++ / MFC

#include<graphics.h>
void drawrect(int l,int t,int r,int d,int col){
  if(col==0)setcolor(RED);
  else setcolor(BLUE);
  rectangle(l,t,r,d);
}
void drawpiece(int l,int t,int r,int d,int col){
  for(int i=1;i<5;i++)
    drawrect(i*16+l,t,i*16+r,d,col);
}
/*DWORD WINAPI Thread2(void* lparam){
  int px2=161,py2=17;
  for(int i=0;i<10;i++,py2+=16,delay(100))
    drawpiece(px2,py2,px2+16,py2+14,1);
}*/
int main()
{   
    initwindow(600,600,"TEST");   
 //   CreateThread(0,0,&Thread2,NULL,0,0);
    int px1=17,py1=17;
    for(int i=0;i<10;i++,py1+=16,delay(100))
      drawpiece(px1,py1,px1+14,py1+14,0);    

    int px2=161,py2=17;
    for(int i=0;i<10;i++,py2+=16,delay(100))
      drawpiece(px2,py2,px2+16,py2+14,1);

    getch();
    return EXIT_SUCCESS;
}

yudhistira dewanata wrote:

First thing first, what actually happen when you multithread? Does the processor run two or more processes independently at the same time , or does it still need to switch between processes?

because if it does run the two separately then why would it need to switch context?

yudhistira dewanata wrote:

i'm guessing the function drawrect() can't be used at the same time and thus needs to be switched between processes. by logic, will it work if i apply semaphores to it?