freepascal.compiler/docs/syntax/symbol.syn

\begin{diagram}{Recognised symbols}{symbols}
\begin{mysyntdiag}
\synt{letter} \begin{stack} \lit*{A ... Z} \\ \lit*{a ... z} \end{stack} 
\end{mysyntdiag}
\begin{mysyntdiag}
\synt{digit}  \lit*{0 ... 9}
\end{mysyntdiag}
\begin{mysyntdiag}
\synt{hex\ digit} 
\begin{stack} \lit*{0 ... 9} \\ \lit*{A ... F} \\ \lit*{a ...f} \end{stack} 
\end{mysyntdiag}
\end{diagram}