Thread: Why doesn't this function take in any parameters?

Hello! I'm working on the game of fifteen from the CS50's Pset3. I'm very confused why the function that initializes the board doesn't take in any parameters. Why doesn't it take the size of the board (d) as its parameter?

Code:

/** * Initializes the game's board with tiles numbered 1 through d*d - 1
 * (i.e., fills 2D array with values but does not actually print them).
 */

void init(void)

Oh, I see... so if the variable as global there's no need to specify it as a parameter?

Here's the whole code, maybe it'll be clearer

Code:

/** * fifteen.c
 *
 *
 * whereby the board's dimensions are to be d x d,
 * where d must be in [DIM_MIN,DIM_MAX]
 */


#define _XOPEN_SOURCE 500


#include <cs50.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>


// constants
#define DIM_MIN 3
#define DIM_MAX 9


// board
int board[DIM_MAX][DIM_MAX];


// dimensions
int d;


// saved locations of the blank tile
int blank_row;
int blank_col;


// prototypes
void clear(void);
void greet(void);
void init(void);
void draw(void);
bool move(int tile);
bool won(void);
void swap(int *a, int *b);
void print_grid_row(int d);
void print_tile(int tile);


int main(int argc, string argv[])
{
    // ensure proper usage
    if (argc != 2)
    {
        printf("Usage: fifteen d\n");
        return 1;
    }


    // ensure valid dimensions
    d = atoi(argv[1]);
    if (d < DIM_MIN || d > DIM_MAX)
    {
        printf("Board must be between %i x %i and %i x %i, inclusive.\n",
            DIM_MIN, DIM_MIN, DIM_MAX, DIM_MAX);
        return 2;
    }


    // open log
    FILE *file = fopen("log.txt", "w");
    if (file == NULL)
    {
        return 3;
    }


    // greet user with instructions
    greet();


    // initialize the board
    init();


    // accept moves until game is won
    while (true)
    {
        // clear the screen
        clear();


        // draw the current state of the board
        draw();


        // log the current state of the board (for testing)
        for (int i = 0; i < d; i++)
        {
            for (int j = 0; j < d; j++)
            {
                fprintf(file, "%i", board[i][j]);
                if (j < d - 1)
                {
                    fprintf(file, "|");
                }
            }
            fprintf(file, "\n");
        }
        fflush(file);


        // check for win
        if (won())
        {
            printf("ftw!\n");
            break;
        }


        // prompt for move
        printf("Tile to move: ");
        int tile = get_int();


        // quit if user inputs 0 (for testing)
        if (tile == 0)
        {
            break;
        }


        // log move (for testing)
        fprintf(file, "%i\n", tile);
        fflush(file);


        // move if possible, else report illegality
        if (!move(tile))
        {
            printf("\nIllegal move.\n");
            usleep(500000);
        }


        // sleep thread for animation's sake
        usleep(50000);
    }


    // close log
    fclose(file);


    // success
    return 0;
}


/**
 * Clears screen using ANSI escape sequences.
 */
void clear(void)
{
    printf("\033[2J");
    printf("\033[%d;%dH", 0, 0);
}


/**
 * Greets player.
 */
void greet(void)
{
    clear();
    printf("WELCOME TO GAME OF FIFTEEN\n");
    usleep(2000000);
}


/**
 * Initializes the game's board with tiles numbered 1 through d*d - 1
 * (i.e., fills 2D array with values but does not actually print them).
 */
void init(void)
{


}


/**
 * Prints the board in its current state.
 */
void draw(void)
{


}


/**
 * If tile borders empty space, moves tile and returns true, else
 * returns false.
 */
bool move(int tile)
{
    return false;
}


/**
 * Returns true if game is won (i.e., board is in winning configuration),
 * else false.
 */
bool won(void)
{
    // TODO
    return false;
}

Salem, laserlight, thank you for the explanation!