Generate randomized 256MB files onto your drive.(C++)

/*generates 256MB randomized files*/
#include <iostream>
#include <fstream>
#include <vector>
#include <time.h>
#include <stdlib.h>
#include <string>
#include <sstream>
using namespace std;

void seed_kilo(string &kilo_seed)
{
    /*Reducing most of the rand() calls here, that reduces most of the CPU time.*/
    for(unsigned int j = 0; j < 1024; j++) {
        kilo_seed += (const char)rand()%256;
    }
}

void reseed_kilo(string &kilo_seed)
{
    char n = rand()%256;

    for(unsigned int j = 0; j < 1024; j++) {
        kilo_seed[j] = (const char)(kilo_seed[j] ^ n);
    }
}

void randomize_quarter_gig(vector<string> &quarter_gig, string &kilo_seed)
{
    string temp;
    char n = rand()%256;

    for(unsigned int i = 0; i < quarter_gig.size(); i++) {
        temp.clear();
        n = n ^ i; /*linear progression, but it's fast and random enough*/

        for(unsigned int j = 0; j < 1024; j++) {
            temp += (const char)(n ^ kilo_seed[j]);
        }

        quarter_gig[i] = temp;
    }
}

int main()
{
    vector<string>  quarter_gig(262144);
    string          temp, kilo_seed, input;
    ofstream        file;
    unsigned int    how_many = 0;
    char            num[4];

    srand(time(NULL));
    seed_kilo(kilo_seed);

    cout << "How many randomized 256MB files to generate ?--> ";
    getline(cin, input);
    stringstream(input) >> how_many;

    for(int i = 0; i < how_many; i++) {
        itoa(i, num, 10);
        temp = "stuff";
        temp += num;

        file.open(temp.c_str(), ofstream::out);

        if(!file.is_open())
            return(1);

        randomize_quarter_gig(quarter_gig, kilo_seed);

        cout << "256MB randomized.\n";

        for(unsigned int j = 0; j < quarter_gig.size(); j++) {
            file.write(quarter_gig[j].c_str(), quarter_gig[j].size());
        }

        file.close();

        cout << "File #" << (i+1) << " written." << "\n";

        if(i != (how_many - 1)) {
            reseed_kilo(kilo_seed);
        }
    }

    return(0);
}