Abstract

A digital computer system is described as comprising an input data circuit, a processor for executing a program stored in a memory to process the inputted data, a depletable energy source (e.g., a battery) for energizing the elements of the computer system, and a power control circuit for selectively controlling the drain imposed upon the energy source in accordance with the data input into the system and the program executed by the processor. In an illustrative embodiment of this invention, the power control circuit is operative in at least three modes of operation, namely off/rest, power down, and operating. In the off/rest mode, the power control circuit imposes a minimum power drain upon the depletable energy source. An operator may manipulate a switch or actuation means to apply a transition signal to the power control, whereby the computer system is disposed from its off/rest mode to its power down mode. In the power down mode, the control circuit applies power at an intermediate level to the data input means. In an illustrative embodiment of this invention, the data input means includes a keyboard and a decoder for providing a signal indicative that one of the keys has been depressed. Upon actuation of the key, a data available signal DA is transmitted to the power control circuit, whereby the computer system is disposed in its operating mode, wherein all of the elements of the computer system are energized at a high power level. In its operating mode, the processor and its memory are fully energized to execute the stored program.