Thread: scanf/printf unexpected behavior

  1. #1
    Registered User
    Join Date
    Oct 2010

    scanf/printf unexpected behavior

    Ok, so over the summer I started making a simple tic-tac-toe program in my spare time to get some practice with pointers, structs, and programming in C in general. Overall, the program has been going great, no major issues. However, there is one area I am having a bit of confusion.

    When I started this project, at the beginning of the summer, I had only a small understanding of C, with my first CS class being in C++. As such, I was not too familiar with how to read input from stdin, so I ended up using getchar(). Now, I am trying to change my input to use scanf() instead. At one point in particular, this is causing some small issues. Reference the code block below:

    int main(int argc, char **argv)
            if (system("cls"))
            printf("TicTacToe v1.0\nBy Daniel Bauer\n\n");
            printf("Number of games to play: ");
            int games, i;
            if(scanf("%d", &games) == 0)
                    printf("Input error, expected integer\n");
                    return 0;
            for(i = 0; i < games; i++)
                    if (system("cls"))
                    board *gameBoard = initializeBoard( );
                    while(gameBoard->human != 'X' && gameBoard->human != 'O')
                            printf("Pick X or O: ");
                            scanf("%c", &gameBoard->human);
                            gameBoard->human = toupper(gameBoard->human);
                    if(gameBoard->human == 'X')
                            gameBoard->computer = 'O';
                            gameBoard->computer = 'X';
    This part of code is supposed to read in the number of games the user wants to play and then whether the player wants to be X or O. The problem is that when the program gets to asking the player X or O, it will print "Pick X or O: Pick X or O: ", when I would prefer it only print that once.

    Does anyone here know what might be causing this? Any help with fixing my code or a workaround would be appreciated.

    And if for whatever reason you need to see more of the code, just let me know!

  2. #2
    Join Date
    Dec 2007

  3. #3
    Registered User
    Join Date
    Oct 2010
    Hmmm, okay. I guess I'll try implementation with another method of reading in from stdin... Didn't realize scanf() could be so flawed... Oh well, onward to rewriting
    Last edited by DanV2; 10-11-2010 at 11:25 AM.

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