Математический анализ кода программы. Как работает rand()?

#include <iostream>
#include <cstring>
#include <ctime>
 
using namespace std;
int main()
{
    char b;
    int k;
    srand(time(NULL));
 
    char article[][6] = { "the", "a", "one", "some", "any"};
    char noun[][6] = { "boy", "girl", "dog", "town", "car"};
    char verb[][9] = { "drove", "jumped", "ran", "walked", "skipped"};
    char preposition[][7] = { "to", "from", "over", "under", "on"};
 
    for (int i = 1; i <= 20; i++)
    {
        char news[255];
        k = rand() % 5;
        b = toupper(article[k][0]);
        news[0] = '\n';
        strcpy_s(news, article[k]);
        news[0] = b;
        strcat_s(news, " ");
        k = rand() % 5;
        strcat_s(news, noun[k]);
        strcat_s(news, " ");
        k = rand() % 5;
        strcat_s(news, verb[k]);
        strcat_s(news, " ");
        k = rand() % 5;
        strcat_s(news, preposition[k]);
        strcat_s(news, " ");
        k = rand() % 5;
        strcat_s(news, article[k]);
        strcat_s(news, " ");
        k = rand() % 5;
        strcat_s(news, noun[k]);
        strcat_s(news, ".");
        cout << news << endl;
    }
 
    
    system("pause");
    return 0;
 
}

srand(time(NULL));