The Macintosh Portable is a portable computer designed, manufactured and sold by Apple Computer, Inc. from September 1989 to October 1991. It is the first battery-powered Macintosh, which garnered significant excitement from critics, but sales to customers were quite low. It featured a fast, sharp, and expensive black and white active matrix LCD screen in a hinged design that covered the keyboard when the machine was not in use. The Portable was one of the early consumer laptops to employ an active matrix panel, and only the most expensive of the initial PowerBook line, the PowerBook 170, used one, due to the high cost. The cursor pointing function was handled by a built-in trackball that could be removed and located on either side of the keyboard. It used expensive SRAM in an effort to maximize battery life and to provide an "instant on" low power sleep mode. The machine was designed to deliver high performance, at the cost of price and weight.