twoto64$ = "18446744073709551616"
      PRINT "2^64 * 2^64 = " ; FNlongmult(twoto64$, twoto64$)
      END

      DEF FNlongmult(num1$, num2$)
      LOCAL C%, I%, J%, S%, num1&(), num2&(), num3&()
      S% = LEN(num1$)+LEN(num2$)
      DIM num1&(S%), num2&(S%), num3&(S%)
      IF LEN(num1$) > LEN(num2$) SWAP num1$,num2$
      $$^num1&(1) = num1$
      num1&() AND= 15
      FOR I% = LEN(num1$) TO 1 STEP -1
        $$^num2&(I%) = num2$
        num2&() AND= 15
        num3&() += num2&() * num1&(I%)
        IF I% MOD 3 = 1 THEN
          C% = 0
          FOR J% = S%-1 TO I%-1 STEP -1
            C% += num3&(J%)
            num3&(J%) = C% MOD 10
            C% DIV= 10
          NEXT
        ENDIF
      NEXT I%
      num3&() += &30
      num3&(S%) = 0
      IF num3&(0) = &30 THEN = $$^num3&(1)
      = $$^num3&(0)