type AnsiChar = Char;
AnsiChar is an 8 bit char type. Currently, it is the same as Char, but this might change in the future, once wide chars (16 bit chars) will be introduced into GPC. Depending on the platform, Char might be either AnsiChar or WideChar then.
AnsiChar is a Borland Delphi extension.
program AnsiCharDemo; var A: AnsiChar; { There is nothing special with `AnsiChar'. } B: Char; begin A := 'A'; A := B end.