Supercalculator

Design and Implement an object (struct/class) that represents
positive integers with an unlimited number of digits, and
provides the four basic arithmetic operations of add, subtract,
multiply, and divide. There should also be a print method and
suitable constructor(s), a destructor, and a factorial function.

This assignment is in two parts. Division is much more difficult
to get right than the other operations. For part 1, you don't need
to implement division at all.

Example use: you don't have to conform to this example exactly,
but be close in spirit at least.

    { bignum * a = new bignum("123456");
      bignum * b = new bignum("10000000000001000000000001");
      bignum * c = new bignum("13");
      bignum * d = add(multiply(a, b), c);
      bignum * e = factorial(new bignum("7"))
      d->print();
      cout << "\n 7! = ";
      e->print();

should print
      1234560000000123456000000123469
      5040

As a test sample, this is the factorial of 500:

   12201368259911100687012387854230469262535743428031
   92842192413588385845373153881997605496447502203281
   86301361647714820358416337872207817720048078520515
   93292854779075719393306037729608590862704291745478
   82424912726344305670173270769461062802310452644218
   87878946575477714986349436778103764427403382736539
   74713864778784954384895955375379904232410612713269
   84327745715546309977202781014561081188373709531016
   35632443298702956389662891165897476957208792692887
   12817800702651745077684107196243903943225364226052
   34945850129918571501248706961568141625359056693423
   81300885624924689156412677565448188650659384795177
   53608940057452389403357984763639449053130623237490
   66445048824665075946735862074637925184200459369692
   98102226397195259719094521782333175693458150855233
   28207628200234026269078983424517120062077146409794
   56116127629145951237229913340169552363850942885592
   01872743379517301458635757082835578015873543276888
   86801203998823847021514676054454076635359841744304
   80128938313896881639487469658817504506926365338175
   05547812864000000000000000000000000000000000000000
   00000000000000000000000000000000000000000000000000
   00000000000000000000000000000000000

it has 1135 digits, the last 124 are all zeros.

Do not #include <vector>. Your big numbers should certainly
store their digits in the way that a vector stores things,
but you should implement the mechanism yourself.
   Unless you get really stuck. If you just can't get it
working, you can #include <vector>, but there will be a
non-trivial penalty in the grade.

Part 2:
   Add a division operation (whole numbers only) and the
ability to handle negative numbers.
   Hint: keep your simple add, subtract, multiply, etc
functions that assume everything is positive. They will
do all the work. Just make new functions that look at the
signs of the inputs, use the old functions, and adjust the
results accordingly.