(RTL) 1. A kind of hardware description language (HDL) used in describing the registers of a computer or digital electronic system, and the way in which data is transferred between them. 2. An intermediate code for a machine with an infinite number of registers, used for machine-independent optimisation. RTL was developed by Chris Fraser and J. Davidson at the University of Arizona in the early 1980s. RTL is used by the GNU C compiler, gcc and by Davidson's VPCC (Very Portable C compiler).