Just my implemetation of tic tac toe game

tic tac toe.c

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

static char grid[3][3];

static char player1 = 'O';
static char player2 = 'X';
int winner = 0;

void printGameGrid();
void insertSymbol(int position, int whichPlayer);
char *getPlayer(int whichPlayer);
void printHelper();
void prefillGrid();
void checkHorizontals();
void checkVerticals();
void checkDiagonals();

int main(int agrc, char **argv)
{
    int whichPlayer = 0;
    int position;

    prefillGrid();
    while (!winner)
    {
        printHelper();
        puts("");
        printGameGrid();
        if (whichPlayer)
        {
            puts("It's player 1's turn");
        }
        else
            puts("It's player 2's turn");
        printf("Enter the position to insert your symbol : ");
        scanf("%d", &position);
        insertSymbol(position, whichPlayer);
        checkHorizontals();
        checkVerticals();
        checkDiagonals();
        whichPlayer = ~whichPlayer;
    }
    return 0;
}

void printGameGrid()
{
    for (int i = 0; i < 3; i++)
    {
        for (int j = 0; j < 3; j++)
        {
            if (grid[i][j] != 'E')
            {
                printf("%c ", grid[i][j]);
            }
            else
                printf(" ");
        }
        puts("");
    }
}

void insertSymbol(int position, int whichPlayer)
{
    if (position == 1)
    {
        if (grid[0][0] == 'E')
        {
            grid[0][0] = getPlayer(whichPlayer);
        }
        else
            puts("Cannot insert here");
    }
    else if (position == 2)
    {
        if (grid[0][1] == 'E')
        {
            grid[0][1] = getPlayer(whichPlayer);
        }
        else
            puts("Cannot insert here");
    }
    else if (position == 3)
    {
        if (grid[0][2] == 'E')
        {
            grid[0][2] = getPlayer(whichPlayer);
        }
        else
            puts("Cannot insert here");
    }
    else if (position == 4)
    {
        if (grid[1][0] == 'E')
        {
            grid[1][0] = getPlayer(whichPlayer);
        }
        else
            puts("Cannot insert here");
    }
    else if (position == 5)
    {
        if (grid[1][1] == 'E')
        {
            grid[1][1] = getPlayer(whichPlayer);
        }
        else
            puts("Cannot insert here");
    }
    else if (position == 6)
    {
        if (grid[1][2] == 'E')
        {
            grid[1][2] = getPlayer(whichPlayer);
        }
        else
            puts("Cannot insert here");
    }
    else if (position == 7)
    {
        if (grid[2][0] == 'E')
        {
            grid[2][0] = getPlayer(whichPlayer);
        }
        else
            puts("Cannot insert here");
    }
    else if (position == 8)
    {
        if (grid[2][1] == 'E')
        {
            grid[2][1] = getPlayer(whichPlayer);
        }
        else
            puts("Cannot insert here");
    }
    else if (position == 9)
    {
        if (grid[2][2] == 'E')
        {
            grid[2][2] = getPlayer(whichPlayer);
        }
        else
            puts("Cannot insert here");
    }
}

char *getPlayer(int whichPlayer)
{
    if (!whichPlayer)
        return player1;
    else
        return player2;
}

void printHelper()
{
    int count = 0;
    for (int i = 0; i < 3; i++)
    {
        for (int j = 0; j < 3; j++)
        {
            count += 1;
            printf("%d ", count);
        }
        puts("");
    }
}

void prefillGrid()
{
    for (int i = 0; i < 3; i++)
    {
        for (int j = 0; j < 3; j++)
        {
            grid[i][j] = 'E';
        }
    }
}

void checkHorizontals()
{
    for (int i = 0; i < 3; i++)
    {
        if ((grid[i][0] == grid[i][1]) && (grid[i][1] == grid[i][2]) && (grid[i][0] != 'E'))
        {
            winner = 1;
            if (grid[i][0] == player1)
            {
                puts("Player 1 won");
            }
            else if (grid[i][0] == player2)
            {
                puts("Player 2 won");
            }
        }
    }
}

void checkVerticals()
{
    for (int i = 0; i < 3; i++)
    {
        if ((grid[0][i] == grid[1][i]) && (grid[1][i] == grid[2][i]) && (grid[0][i] != 'E'))
        {
            winner = 1;
            if (grid[0][i] == player1)
            {
                puts("Player 1 won");
            }
            else if (grid[0][i] == player2)
            {
                puts("Player 2 won");
            }
        }
    }
}

void checkDiagonals()
{
    if ((grid[0][0] == grid[1][1]) && (grid[1][1] == grid[2][2]) && (grid[0][0] != 'E'))
    {
        winner = 1;
        if (grid[0][0] == player1)
        {
            puts("Player 1 won");
        }
        else if (grid[0][0] == player2)
        {
            puts("Player 2 won");
        }
    }
    else if ((grid[0][2] == grid[1][1]) && (grid[1][1] == grid[2][0]) && (grid[0][2] != 'E'))
    {
        winner = 1;
        if (grid[0][2] == player1)
        {
            puts("Player 1 won");
        }
        else if (grid[0][2] == player2)
        {
            puts("Player 2 won");
        }
    }
}