Reading data into a 2D array

This is a discussion on Reading data into a 2D array within the C Programming forums, part of the General Programming Boards category; Hi I thought id challenge myself and make a small and very very basic graphics turtle logo program to plot ...

  1. #1
    Its hard... But im here swgh's Avatar
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    Reading data into a 2D array

    Hi I thought id challenge myself and make a small and very very basic
    graphics turtle logo program to plot graph points then prints them out.

    What I am having trouble the most with is reading input from the keyboard
    into the 2D array I passed from the main function. The below program is
    not finished but it was what I have managed to do so far... it does compile but obviously so far doesnt quite work.

    I have looked through my book and nothing tells me how to do this, I now
    how to print out a declared 2D array but Im not sure how to read the coordinates into it from the keyboard. I guess what I have attempted is totally
    wrong, and I gather using scanf() is wrong too.

    heres what I have so far:

    Code:
    #include <stdio.h>
    
    #define MAX_HEIGHT 20
    #define MAX_LENGTH 20
    #define TRUE 1
    #define FALSE 0
    
    /*function prototype*/
    int mainMenu ( char[][] );
    
    /*main function - begins program execution -----------------------------------*/
    int main ( void )
    {
       char board[ MAX_HEIGHT ][ MAX_LENGTH ] =
       {
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' },
          { '0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0' }
       };
    
       mainMenu ( board );
    
       getchar(); /*freeze console output window*/
    
       return 0; /*return value from int main*/
    }
    
    /*function to display the main menu*/
    int mainMenu ( char bd[][ 20 ] )
    {
       int choice = TRUE;
       int penUp = TRUE;
       int i, j;
    
       do
       {
          printf("\tTURTLE LOGO GRAPHICS\n\n"
                 "1 Place Pen Up\n"
                 "2 Place Pen Down\n"
                 "3 Draw\n"
                 "4 Show Grid\n"
                 "5 Quit\n"
                 "> ");
          scanf("%d", &choice);
    
          switch ( choice )
          {
          case 1:
             if ( penUp == TRUE )
             {
                puts("\nThe pen is already up\n");
             }
    
             if ( penUp == FALSE )
             {
                penUp = TRUE;
    
                puts("\nThe pen has been raised up\n");
             }
             break;
    
          case 2:
             if ( penUp == FALSE )
             {
                puts("\nThe pen is already down\n");
             }
    
             if ( penUp == TRUE )
             {
                penUp = FALSE;
    
                puts("\nThe pen has been placed down\n");
             }
             break;
    
          case 3:
             if ( penUp == TRUE )
             {
                puts("\nYou cannot draw with the pen raised up\n");
             }
    
             else
             {
                // This is my trouble part:
    
                printf("Enter the xy coordinates to draw: ");
                scanf("%d", &bd[ MAX_HEIGHT ][ MAX_LENGTH ]);
             }
             break;
    
          case 4:
             puts("\n");
    
             for ( i = 0; i < MAX_HEIGHT; i++ )
             {
                for ( j = 0; j < MAX_LENGTH; j++ )
                   printf("%c", bd[ i ][ j ]);
                   printf("\n");
             }
             puts("\n");
             break;
    
          case 5:
             return 0;
             break;
    
          default:
             printf("\n\n");
             break;
          }
       } while ( choice );
    }
    I'm just trying to be a better person - My Name Is Earl

  2. #2
    Woof, woof! zacs7's Avatar
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    There is an easier way to initialize the array to '0', why not fill it with memset()?
    Code:
    memset(board, '0', MAX_HEIGHT + MAX_WIDTH);
    (I think )

    You have to map the coords to the array, for example have a starting point and an ending point.

    say, (x1, y1) = start and (x2, y2) = end, for drawing lines - requires a bit of maths.

    Or simply to draw a dot, ask for x and y (each will be an offset from the start of the array), ie the upper left hand 'cell' is (0, 0). I'd use fgets() to read the line (after firstly flushing stdin - see the FAQ) then sscanf() to read whatever format on that line, checking if the coords are in-bounds then set the point to whatever character.

    Unless I've missed the point of your problem?
    Last edited by zacs7; 08-17-2007 at 02:55 AM. Reason: Moronic idea

  3. #3
    Its hard... But im here swgh's Avatar
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    No thats perfect thanks zacs7 I appreicate that.
    I'm just trying to be a better person - My Name Is Earl

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