Trigraph sequences

Trigraph sequences are three-character sequences that are replaced by a corresponding single character in Translation Phase 1, as follows:

??=	#	??(	[	??<	{
??/	\	??)	]	??>	}
??'	^	??!	|	??-	~

Digraph sequences behave the same as their corresponding single characters in all respects except fo rtheir spelling. Thus

   <:  :>  <%  >%  %:  %:%:

   [   ]   {   }   #   ##

No other such sequences are recognized. The trigraph sequences provide a way to specify characters that are missing on some terminals, but that the C language uses.