(*     tab p;
 *
 *      Kermit basic operations.
 *      
 *)


    function    ToChar ( ch : char ): char;
    begin
        (* make sure not a control character *)
        ToChar := chr( ord ( ch ) + ord ( ' ' ) );
    end;

    function    UnChar ( ch : char ): char;
    begin
        (* undoes ToChar *)
        UnChar := chr ( ord ( ch ) - ord ( ' ' ) );
    end;

    function    Ctl ( ch : char ): char;
    begin
        (* toggle control bit *)
        Ctl := cxor ( ch , chr ( 64 ) );
    end;

    function    MakeCheck ( chksum : integer ): char;
    begin
        MakeCheck := ToChar (
                              chr (
                                    ( chksum +
                                    iand ( chksum , 192 ) div 64 )
                                          mod 64
                                  )
                            );
    end;

    function    StripParity ( ch : char ) : char;
    begin
        StripParity := chr( iand( ord( ch ), 127 ) );
    end;

    function Prev ( n : integer ):integer;
    begin
        if n = 0 then
            Prev := 63
        else
            Prev := n - 1;
    end;

    function    uc( ch : char ):char;
    begin
        if ( ch >= 'a' ) and ( ch <= 'z' ) then
            uc := chr( ord(ch) - 32 )
        else
            uc := ch;
    end;