Abstract: An MOS RAM read/write memory system has thirty-two 1 .times. 512 bit RAM memory chips arranged in a matrix. The system pretests all data bit locations for each address prior to the entry of any data into that address, and automatically skips an address having a faulty data bit location in it. In addition, the system functions, upon reading out of data information from the memory chips, to uniquely identify any faulty MOS RAM memory chip; so that it may be removed and replaced if desired.

Abstract: A digital card reader is connected to supply input data to a random access memory corresponding to pre-coded information on cards inserted into the reader. The insertion of a card into the reader causes a binary counter to advance one binary count to address the next location in the memory for storing the data on the card. The outputs of the binary counter, which have encoded thereon the binary addresses, are further coupled to a digital-to-analog converter having an output lead on which an analog representation of the selected address appears. This output lead of the digital-to-analog converter is used to operate an analog meter, such as an ammeter, having a scale calibrated to indicate the degree of fullness of the memory as determined by the binary encoded address information.