function value ch_is_alphanumeric ( c )

%% CH_IS_ALPHANUMERIC = the character C is alphanumeric.
%
%  Discussion:
%
%    Alphanumeric characters are 'A' through 'Z', 'a' through 'z' and
%    '0' through '9'.
%
%  Modified:
%
%    01 May 2004
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, character C, the character to be checked.
%
%    Output, logical VALUE, is TRUE if the character is
%    alphabetic or numeric.
%
  FALSE = 0;
  TRUE = 1;
 
  if ( ( 'a' <= i & i <= 'z' ) | ...
       ( 'A' <= i & i <= 'Z' ) | ...
       ( '0' <= i & i <= '9' ) )

    value = TRUE;

  else

    value = FALSE;

  end