Synchronous Data Link Control <communications> (SDLC) An {IBM} {protocol}. A discipline conforming to subsets of the {ADCCP} of {ANSI} and the {HDLC} of the {International Organization for Standardization}. SDLC manages synchronous, code-transparent, bit-serial communication which can be {duplex} or {half-duplex}; switched or non-switched; {point-to-point}, {multipoint}, or loop. Compare {Binary Synchronous Communication}. (1995-03-22)