The information and comments contained in this PREFACE should not be considered part of the Standard. They have been included for clarification and guidance purposes only.

American National Standard Code for Information Interchange (ANSI X3.4) is designed to achieve coding uniformity for information interchange betweend ata processing and communication systems. The increasing use of computers and related equipment for preparation of perforated tape for numerical machine control and for conlmunication between various conlponents of advanced numerically controlled systems has demonstrated the need for standardized usage for numerical control. As a result, the EIA 1E-3 1 Committee,which is made up of representatives of control system builders, machine builders, and users,has prepared this Standard for use by people building and using numerical control equipment.

The chnracter coding described in this Standard does not supersede that described in EIA Standard RS-244 ("Character Code for Numerical Machine Control Perforated Tape"). However, users and builders of numerically controlled equipment should be aware that the flexibility and expansiboilfi ttyh e code described in this Standard make it more applicable than RS-244 for newer, advanced numerical control systems. Future standardization work by the EIA committee on Numerical Control Systems and Equipment will assume the use ol the code described in this Standard for machine programs.

Users of this Standard should refer to the latest revision of EIA Standard EIA-274 (,"Interchangeable Variable Block Data Format for Positioning, Contouring, and Contouring/positioning Numerically Controlled Machines") for details on the format and definition of characters.