start_up = proc ()
    po: stream := stream$primary_output()

    % To turn a character code into an integer, use char$c2i
    % (but then to print it, it needs to be turned into a string first
    % with int$unparse)
    stream$putl(po, int$unparse( char$c2i( 'a' ) ) ) % prints '97'

    % To turn an integer into a character code, use char$i2c
    stream$putc(po, char$i2c( 97 ) );  % prints 'a'
end start_up