implicit declaration of function 'putw, and a segfault?

Question

The error I'm getting is:

p1.c: In function 'WriteToFile': p1.c:219:2: warning: implicit declaration of function 'putw' [-Wimplicit-function-declaration]

Not sure how to fix the problem. I'm also getting a segmentation fault. The code compiles fine, but when running the code I get the segfault. I'm assuming the error I'm getting is linked to the segmentation fault? If someone could provide some insight or propose a solution, that would be greatly appreciated.

edit: The segfault is occurring at "int k2 = atoi(argv[2]);", still don't know what's causing it though.

#include<stdio.h>
#include<string.h>
#include<math.h>
#include<stdlib.h>
#pragma warning(disable : 4996).


typedef struct person_
{
    int ID;
    int mask;
    int vaccine;
    int status;
    int days_infected;
    int days_quarantined;

}Person;
#define POPULATION 500

static int vaccinated;
static int infected;
static int masked;
static int healthy;
static int oldinfected;



Person meetrandomly(FILE* IN, Person M, Person N[])
{
    //reading from the pre formatted file!!!!!!!
    float p_infected[4];
    float np = 0, hwf = 0, iwf = 0, hv = 0;
    fscanf(IN, "%*s %*s %*s %*s  %*s %*s  %*s %*s %f", &np);
    fscanf(++IN, "%*s %*s %*s %*s  %*s %*s  %*s  %*s  %*s  %*s  %*s %f", &hwf);
    fscanf(++IN, "%*s %*s %*s %*s  %*s %*s  %*s  %*s  %*s  %*s  %*s %f", &iwf);
    fscanf(++IN, "%*s %*s %*s %*s  %*s %*s  %*s  %*s %f", &hv);
    p_infected[0] = np;
    p_infected[1] = hwf;
    p_infected[2] = iwf;
    p_infected[3] = hv;
    /////////////////////////////////////////////////////////


    int n = rand() % 20 + 1;
    int i;
    for (i = 0;i < n;i++)
    {
        float* poniter1 = NULL;
        int m = rand() % POPULATION;
        Person temp = N[m];
        if (M.status == 0 && N[m].status == 0)
        {
            return M;
        }
        else if (M.status == 0 && N[m].status == 1)
        {
            if (M.mask == 0 && N[m].mask == 0)
            {

                int num = rand() % 100 + 1;
                int n = p_infected[0]*100;
                if (M.vaccine == 1)
                {
                    n = n / 10;
                }
                if (num < n)
                {
                    M.status = 2;
                    M.days_infected = 0;
                    infected++;

                }


            }
            else if (M.mask == 0 && N[m].mask == 1)
            {
                int num = rand() % 100 + 1;
                int n = p_infected[2]*100;
                if (M.vaccine == 1)
                {
                        n = n / 10;
                }
                if (num < n)
                {
                    M.status = 2;
                    M.days_infected = 0;
                    infected++;
                }

            }
            else if (M.mask == 1 && N[m].mask == 0)
            {

                int num = rand() % 100 + 1;
                int n = p_infected[1]*100;
                if (M.vaccine == 1)
                {
                    n = n / 10;
                }
                if (num <= n)
                {
                    M.status = 2;
                    M.days_infected = 0;
                    infected++;
                }
            }
            else if (M.mask == 1 && N[m].mask == 1)
            {
                int num = rand() % 100 + 1;
                int n = (hwf*iwf)*100;
                if (M.vaccine == 1)
                {
                    n = n / 100;
                }
                if (num > (100-n))
                {
                    M.status = 2;
                    M.days_infected = 0;
                    infected++;
                }

            }


        }
    }
    return M;

}
void Simulation(FILE* A, Person M[])
{
    int i;
    for (i = 0; i < POPULATION; i++)
    {
        M[i] = meetrandomly(A, M[i], M);
        M++;

    }
}
Person* updation(Person B[])
{
    oldinfected = infected;
    int i;
    for (i = 0;i < POPULATION;i++)
    {
        if (B[i].status == 1 && B[i].days_infected < 14)
        {
            B[i].days_infected++;
        }
        else if (B[i].status == 1 && B[i].days_infected > 14)
        {
            B[i].status = 0;
            infected--;
            healthy++;
        }
        else if (B[i].status == 3 && B[i].days_quarantined > 14)
        {
            B[i].status = 0;
            infected--;
            healthy++;
        }
    }
    return B;
}
Person* Initialization(FILE* IN, Person N[], int k2, int k3, int k4, int k5, int *vaccinated, int *infected, int *healthy, int* masked)
{
    

    //allocating the array with the necessary values!
    /*(1) N* k2 initially infected person randomly; (2) N* k3 random person who
        will wear face masks every day; (3) N* k4 random person who have been vaccinated; (4)
        for each infected person, whether he / she is quarantined.The N - Person population should
            be updated accordingly.*/


    k2 = (POPULATION * k2) / 100;
    *(infected)= k2;
    k3 = (POPULATION * k3) / 100;
    k4 = (POPULATION * k4) / 100;
    *(vaccinated) = k4;
    k5 = (POPULATION * k5) / 100;
    *(masked) = k5;

    int i;
    for (i = 0;i < k2;i++)
    {
        N[i].days_infected = 0;
        N[i].status = 2;
        int k = rand() % 100;
        if (k > k5)
        {
            N[i].status = 3;
            N[i].days_quarantined = 0;
        }
        else
        {
            N[i].status = 2;
            N[i].days_infected = 0;

        }

    }
    int j;
    for (j = k2;j < (k3)+(k2);j++)
    {
        N[j].mask = 1;

    }
    int k;
    for (k = k3;k < ((k3)+(k4));k++)
    {
        N[k].vaccine = 1;

    }

    return N;
}

void WriteToFile(FILE* OUT, int week)
{
    char str[] = "\n Week";
    fputs(str, OUT);
    putw(week, OUT);
    char str1[] = ",\tHealthy=";
    fputs(str1, OUT);
    putw(healthy, OUT);
    char str2[] = ", \tNew Cases=";
    fputs(str2, OUT);
    putw((infected-oldinfected), OUT);
    char str3[] = ", \tTotal Cases=";
    fputs(str3, OUT);
    putw((infected), OUT);
    
}




int main(int argc, char* argv[])
{
    int days = 0;
    Person A[POPULATION];
    int k2 = atoi(argv[2]);
    int k3 = atoi(argv[3]);
    int k4 = atoi(argv[4]);
    int k5 = atoi(argv[5]);
    if ((k2 < 0 && k2>100) || (k3 < 0 && k3>100) || (k4 < 0 && k4>100) || (k5 < 0 && k5>100))
    {
        printf(" \n Please enter k2's, k3's, k4's, k5's value to be between 1 and 100 and try again.");
        return 0;
    }
    FILE* IN = fopen(argv[6], "r");
    FILE* OUT = fopen(argv[7], "w");
    if (IN < 0 || OUT < 0) { perror("\n No such file found!!\n"); exit(1); }
    //reading from the pre-formatted file!!!
    int i, j, k;
    days = 7 * atoi(argv[1]);
    Person *B;
        B= Initialization(IN, A, k2, k3, k4, k5, &vaccinated, &healthy, &infected, &masked);
    for (i = 0; i < days; i++)
    {
        Simulation(IN, B);
        updation(B);
        // add other necessary parameters for the function call
        // this is the key function that does the simulation
        if (i % 7 == 6) // at the end of each week
        {
            int q = i / 7;
            WriteToFile(OUT,q);
        }
        // write the report to the output file
    }
    // close both input and output files
    return 0;
}