procedure S(); procedure A(); begin begin isave:=input_pointer; if input symbol='c'then if input_symbol=a'then begin begin ADVANCE(); ADVANCE(); if A()then if inputSymbol=‘b' then begin if inputSymbol=‘d' ADVANCE();return else; then end begin end ADVANCE(); /*failure to find ab*/ return true input_pointer:=isave; end if inputSymbol=‘a' then end; begin ADVANCE();return true; return false; end end; else return false; end;procedure S( ); begin if input_symbol =‘c’then begin ADVANCE( ); if A( ) then if inputSymbol=‘d’ then begin ADVANCE( ); return true end end; return false; end; procedure A( ); begin isave:= input_pointer; if input_symbol= ‘a’ then begin ADVANCE( ); if inputSymbol = ‘b’ then begin ADVANCE( ); return else; end end /*failure to find ab*/ input_pointer:=isave; if inputSymbol = ‘a’ then begin ADVANCE( ); return true; end else return false; end;