ok thanks a lot Per...that helped...
but another thing, if suppose key '1' is pressed once and it should keep monitoring the inputs for say the whole day & give outputs accordingly,and simultaneously keep checking for any other keypress(and execute the operation for any other key press),how would the code look like?
i did something like...

a=P0^0;
x=P1^0;
while(1)
  {keyscan();
   if key '1' {if(a==1)
               x=1;
               else
               x=0;}
   if key '2' {do this}
   if .....
   .....



   if key '13' {do this}
  }

along with this i need to monitor the value of 'a' infinitely(if key '1' was pressed once),and it should toggle 'x' accordingly,say infinitely.

so how to do that infinite monitoring?

thanks a lot.