Multiplication of very long integers

Question

Is there an algorithm for accurately multiplying two arbitrarily long integers together? The language I am working with is limited to 64-bit unsigned integer length (maximum int

Answer 1

Here is my code piece in C. Good old multiply method

char *multiply(char s1[], char s2[]) {
    int l1 = strlen(s1);
    int l2 = strlen(s2);
    int i, j, k = 0, c = 0;
    char *r = (char *) malloc (l1+l2+1); // add one byte for the zero terminating string
    int temp;

    strrev(s1);
    strrev(s2);
    for (i = 0;i