Cash register which reads tags and other media, automatically checks the accuracy of data, performs computations, instructs and controls operator personnel, prints sales checks, and sends data to a remote processor. Key-less entry of all data is possible by virtue of a reading wand for data recorded magnetically on strips, for example, but an auxiliary keyboard may be provided for extra versatility. Data strips are attached to articles of merchandise, are provided upon an external control panel, and are incorporated in employee badges and customer credit cards. Each strip contains control data as well as at least one of descriptive, quantitative and instruction data. The utilization of a set of strips by an operator implements a complete transaction. The control data are preferably encoded upon each strip as a preamble to the message contained within the strip. Such preambles and the instruction data determine the manner in which the cash register operates to implement a transaction.