The market remains pinned in a narrow range after a powerful rally pushed the broad S & P 500 index up more than 20 percent since mid-March .
The market remains pinned in a narrow range after a powerful rally drove the broad Standard & Poor 's 500 index .SPX up more than 20 percent since mid-March .
defines the hardware, cabling wiring, power output, pulse rate, etc. (osi layer)