The ARPA computer network (ARPANET) is a nationwide network of diverse autonomous computers connected via a message-switching store-and-forward communications subnet using leased wide-band (50-kbit/s) telephone lines. A primary objective of the ARPANET is to share preexisting programs and data. Many of the difficulties of using remotely generated programs and data are found to be simple format incompatibilities requiring data manipulations like character set conversion, header prefacing and stripping, packing and unpacking of repeated data, generating counters and flags, and field transposition. The data reconfiguration service (DRS) is an attempt to provide a convenient way of performing these data manipulations in order to mediate between superficially incompatible data streams connecting existing programs in the ARPANET. Desiring to match two incompatible input-output streams, an applications programmer specifies a data stream transformation (called a form) written in the data reconfiguration language (DRL). Associating the appropriate form name with the connection between his two programs, the programmer causes the DRS to follow his instructions on how the specified data streams are to be manipulated in the communication required to make the two programs cooperate over the ARPANET. Components of the DRS include the specification of its special-purpose data reconfiguration language, a form compiler to translate forms into fast-running transformation programs, an interpreter to perform high-speed data transformations at application program run time, and a standard set of ARPANET protocols for the routine handling of connections and form specifications between operating systems.