How do I make a save/load function in C ?

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C

First of I'm a beginner in programming. I am using C.
And I started of this project to make a connect-4 game which can save the look of the board while playing and load it to continue where it was left of.
Basically I managed to get everything to work perfectly to work except to make a save and load function. I need this save function to be able to be accessed while the game is in progress then ask for a what file name the users wants to give it, then the file to be created with that name and contain the look of the board at the time it was saved.

I studied about creating files and writing reading them .. but i dont understand how is ti possible to do what i need(and even if its possible)

here is the code of the whole game: (even if you dont have the answer any tips for the code would be great)

//libraries included
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

//define included
#define BOARD_ROWS 6
#define BOARD_COLS 7
#define DIM 15

//all functions so i can access them when i need
void printBoard(char *board);
int takeTurn(char *board, int player, const char*);
int checkWin(char *board);
int checkFour(char *board, int, int, int, int);
int horizontalCheck(char *board);
int verticalCheck(char *board);
int diagonalCheck(char *board);
int newGame();
int mainMenu();
void nameInput();

//universal variables
char firstPlayer[DIM], secondPlayer[DIM];

// _____________________________________________ MAIN __________________________________________________
//main function
int main(){
    mainMenu();
}

// _____________________________________________ play new game option __________________________________________________
int newGame(){ //function needs integer value argc(argument count) and char value argv(argument value)

    const char *PIECES = "XO"; //these are the pieces the player use, player one = X player two = O
    char board[BOARD_ROWS * BOARD_COLS]; // the board = board-rows * board-cols which is 7*6=42
    memset(board, ' ', BOARD_ROWS * BOARD_COLS); // this function fills board with the value ' ' and that is to
                                                //be done (board-rows*board-cols) times which is 42 times

    int turn, done = 0;

    for(turn = 0; turn < BOARD_ROWS * BOARD_COLS && !done; turn++){ //looping until done is 0 (which it is by default) AND turn is 46
        printBoard(board);
        while(!takeTurn(board, turn % 2, PIECES)){ //the while will happen until takeTurn returns 0
            printBoard(board);
            puts("**Column full!**\n");//so basically when it returns 0 the column is full
      }//once it returns 1 we move own
        done = checkWin(board);//basically when ever the move goes through victory is checked
   }
        printBoard(board);

    if(turn == BOARD_ROWS * BOARD_COLS && !done){ //if turn is equal to 42 which is the last turn AND done is 0
        puts("It's a tie!");// then its a tie
    } else {//this is where the winner is calculated
        turn--;//41
        printf("Player %d (%c) wins!\n", turn % 2 + 1, PIECES[turn % 2]);//41%2+1=2 , 41%2=1 and PIECES[1] is O or X given a different example
   }
    return 0;//end of program
}

//name input function
void inputName(){
    printf("First player enter your name:\n");
    getchar();//to get the \n before scan takes it
    scanf("%c", firstPlayer);
    printf("Second player enter your name:\n");
    getchar();//to get the \n before scan takes it
    scanf("%c", secondPlayer);

    //maybe like this
    //FILE *firstPlayer;
    //firstPlayer = fopen ("*firstPlayer", "r");
}

void printBoard(char *board){
   int row, col; //counters for loops
   //int legitMove; //int to only allow 1-7 and 0 for save
    //do{
   //system("clear");
   puts("\n    ****Connect Four****\n"); //heading
   for(row = 0; row < BOARD_ROWS; row++){ //6 times
      for(col = 0; col < BOARD_COLS; col++){ //7 times
         printf("| %c ",  board[BOARD_COLS * row + col]); //this prints the character filling in row by row
      }
      puts("|");
      puts("-----------------------------"); // these are to style the look of the board and differentiate between

   }
   puts("  1   2   3   4   5   6   7\n"); //this is for the players to know which column is which and not have to count
}

int takeTurn(char *board, int player, const char *PIECES){ //takes (board, turn % 2, PIECES)
   int row, col = 0;
   printf("Player %c (%c):\nEnter number coordinate: ", player + 1, PIECES[player]); //player+1 is 0+1=1 and so PIECES[1] will be O
//                                                                                                       and so PIECES[0] will be X
while(1){
      if(1 != scanf("%d", &col) || col < 1 || col > 7 ){ //here is the input for the first move it is allowed only in 1-7 values
         while(getchar() != '\n'); //this loop discards unwanted characters and basically gives a clean line to print
         puts("Number out of bounds! Try again.");
      } else {
         break; //if the input is 1-7 then it breaks
      }
   }
   col--;//after that one spot is taken for the players move, that's why it decrements

   for(row = BOARD_ROWS - 1; row >= 0; row--){
      if(board[BOARD_COLS * row + col] == ' '){//if the space selected
         board[BOARD_COLS * row + col] = PIECES[player];//then the space is marked either X or O
         return 1;
      }
   }
   return 0;
}
int checkWin(char *board){
    return (horizontalCheck(board) || verticalCheck(board) || diagonalCheck(board));
}

int checkFour(char *board, int a, int b, int c, int d){
    return (board[a] == board[b] && board[b] == board[c] && board[c] == board[d] && board[a] != ' ');
}

int horizontalCheck(char *board){
    int row, col, index;
    const int WIDTH = 1;

    for(row = 0; row < BOARD_ROWS; row++){
       for(col = 0; col < BOARD_COLS - 3; col++){
          index = BOARD_COLS * row + col;//index is 0 here since 7*0+0 is 0
          if(checkFour(board, index, index + WIDTH, index + WIDTH * 2, index + WIDTH * 3)){
             return 1;
          }
       }
    }
    return 0;
}

int verticalCheck(char *board){
    int row, col, index;
    const int HEIGHT = 7;

    for(row = 0; row < BOARD_ROWS - 3; row++){
       for(col = 0; col < BOARD_COLS; col++){
          index = BOARD_COLS * row + col;
          if(checkFour(board, index, index + HEIGHT, index + HEIGHT * 2, index + HEIGHT * 3)){
              return 1;
          }
       }
    }
    return 0;
}

int diagonalCheck(char *board){
   int row, col, index, count = 0;
   const int DIAG_RGT = 6, DIAG_LFT = 8;

   for(row = 0; row < BOARD_ROWS - 3; row++){
      for(col = 0; col < BOARD_COLS; col++){
         index = BOARD_COLS * row + col;
         if(((count <= 3) && (checkFour(board, index, index + DIAG_LFT, index + DIAG_LFT * 2, index + DIAG_LFT * 3))) ||
         ((count >= 3) && (checkFour(board, index, index + DIAG_RGT, index + DIAG_RGT * 2, index + DIAG_RGT * 3)))){
            return 1;
         }
         count++;
      }
      count = 0;
   }
   return 0;
}

//print main menu and guide through options
int mainMenu(){
    int choiceMainProblem = 0;// I introduce this variable to make the menu only take values 1 2 or 3 and not allow any other
    int choiceMain;
    do{
    printf("Connect-4 game\n");
    printf("1.Play new game\n");
    printf("2.Load already existing game\n");
    printf("3.Exit the game\n");
    printf("\n");
    printf("Choose an option(1-3):\n");//all of the above until here is printing the look of the main menu
    scanf("%d", &choiceMain);

    if((choiceMain > 3) || (choiceMain <1)){
        choiceMainProblem = 1;
        printf("Try again values supported are 1 2 3!\n");
    }
    }
    while(choiceMainProblem);

    switch(choiceMain){
        case 1: inputName(); break;
        //value 2:
        case 3: return 0;
    }
    return 0;
}

What I have tried:

I havent tried anything since i dont know how is it possible