In 1983, the Electronics Industries Association published the standard RS-494, commonly referred to as BCL (binary cutter location) data exchange format. BCL is a means of standardising the formats for NC part programs. Its aim is to eliminate the cost and confusion associated with multiple postprocessors and enable the portability of part programs among different machine tools. In this article we give a short review of BCL and its introduction. We also discuss the nature of BCL data, its implementation aspects and the advantages it offers the NC industry.