Primes C (Working)

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>

#define TRUE 1
#define FALSE 0

int main(int argc, char* argv[])
{
    int n, m, lim;
    double s;
    char* nums;
    char input[255];
    clock_t start, stop;

    if (argc == 2)
        lim = atoi(argv[1]);
    else
    {
        printf("Enter a limit for this search (empty for default): ");
        gets(input);
        if (input[0])
            lim = atoi(input);
        else
            lim = 100000000;
    }

    s = sqrt(lim);

    start = clock();

    nums = (char *)calloc(lim + 1, sizeof(char));

    for (n = 2; n < s; n++)
    {
        if (nums[n] == FALSE)
        {
            m = n * n;
            while (m <= lim)
            {
                nums[m] = TRUE;
                m += n;
            }
        }
    }

    stop = clock();

    printf("It took %f seconds.\n", (double)(stop - start) / 1000);
    printf("Do you want to list the results, count total, or do nothing (L/C/N)? ");
    gets(input);
    if (input[0] == 'L' || input[0] == 'l' || input[0] == 'C' || input[0] == 'c')
    {
        m = 0;
        for (n = 2; n < lim; n++)
        {
            if (nums[n] == FALSE)
            {
                if (input[0] == 'L' || input[0] == 'l')
                    printf("%d\n", n);
                m++;
            }
        }
        printf("Total primes = %d\n\n", m);
        printf("Press ENTER to exit. . . ");
        getchar();
    }

    free(nums);
    return 0;
}