What is Time in force; immediate-or-cancel, fill-or-kill and good-till-cancelled orders?

An order’s time in force says how long its unexecuted part may rest. A day order rests until the end of the session. An immediate-or-cancel order (IOC) executes what it can on arrival and cancels the rest. A fill-or-kill order (FOK) executes in full on arrival or not at all. A good-till-cancelled order (GTC) survives the session’s end and rests until it is executed or cancelled.