\section{Terminology} \label{sec:terminology} \begin{multicols}{2} \begin{description} \item[HNF] Head normal form, the state of a graph node that cannot be rewritten itself (though it children may). \item[ISA] Instruction set architecture. \item[IT block] If-then block, a Thumb construct for conditional execution. \item[LSB(s)] Least significant bit(s), the bit(s) with the lowest value in a word. \item[PC] Program counter, \ual{r15} on ARM. \item[RTS] Run-time system. Clean's run-time system ensures that the \clean{Start} node is reduced and printed. It also takes care of garbage collecting. \item[SP] Stack pointer, \ual{r13} on ARM. \item[UAL] Unified Assembler Language, an assembly language syntax that \enquote{provides a canonical form for all ARM and Thumb instructions} \parencite[A4.2]{armv7m}. \end{description} \end{multicols}