here is a code:

.
.
.
.
.
.
const char key_table[16] = "123A456B789C*0#D";
unsigned char key;
//unsigned char ex0_isr_counter = 0;

void ex0_isr (void) interrupt 0
{
//ex0_isr_counter++;   // Increment the count
unsigned char keypad_scan;
    key = ((keypad_scan=keypad_address)&keypad_mask);
  	key = key_table[key];
	goto_xy(0,0);
	putch_lcd(key); 
}
.
.
.
.
.
.
.
   while(1)
    	{
.
.
.
.
if (key == 4)
{
   goto_xy(2,0);
   putch_lcd(0xe4); 
   Puts("vse-vse");
   }
.
.
.
.
}

 

why in first time the message is printed to lcd (interrupt isr),
and second time is not (if (key == 4)).......
"key" is global variable..........