Trigraph sequences

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

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

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.