Initializing 2D Arrays

     int a[MAX_ROWS][MAX_COLS];

• Write loops to initialize:

       int i,j,k = 0;
  
       for(i = 0; i < MAX_ROWS; i++)
            for(j = 0; j < MAX_COLS; j++)
                 a[i][j] = k++;
  
  

• We could also open a file containing the initial data and read it into the array:

       int i,j;
       FILE *fp;
  
       if((fp = fopen("file","r")) == NULL)
       {     fprintf(stderr,"Unable to open file\n");
             exit(1);
       }
       for(i = 0; i < MAX_ROWS; i++)
            for(j = 0; j < MAX_COLS; j++)
                 fscanf(fp, "%d", &a[i][j]);
       fclose(fp);
  
  

• We can also use an array initializer like we did for 1D arrays. Here it is helpful to think of the 2D array as a 1D array whose elements are 1D arrays. (recall the picture).

       int a[MAX_ROWS][MAX_COLS] = { {1,2,3},
                                     {4,5,6},
                                     {7,8,9}  };