Pointers and 2-Dimensional arrays in C programming

            Multi-dimensional array can also be represented with an equivalent pointer notation as in single dimensional array. A two dimensional array is actually a collection of one dimensional arrays. Therefore we can define a two dimensional array as a pointer to a group of contiguous one-dimensional arrays. Its general syntax is as

  Data_type (*ptr_variable)[expression2];

            Instead of

         Data_type array[expression1][expression2];

   

   Example:

   Suppose x is a two dimensional integer array having 4 rows and 5 columns. We can declare x as

int (*x)[5];

   rather than

int x[4][5];

                    Here, in first declaration, x is defined to be a pointer to a group of contiguous one dimensional 5-element integer arrays. The x points to the first 5-element array, which is actually first row of the two dimensional array. Similarly, x+1 points to the second 5-element array, which is the second row of the two dimensional array. It is illustrated as

An example:

 void main()

     {

  int p[2][3]={   {1,2,3},

                           {4,5,6}

                          };

   clrscr();

   printf("p=%u\tp+1=%u",p,p+1);

   printf("\n*p=%u\t*(p+1)=%u",*p,*(p+1));

   printf("\n*(p+0)+1=%u\t*(p+1)+1=%u",*(p+0)+1,*(p+1)+1);

   printf("\n*(*(p+0)+1)=%u\t*(*(p+1)+1)=%u",*(*(p+0)+1),*(*(p+1)+1));

   getch();

    }

Output:

p=65514                 p+1=65520

*p=65514               *(p+1)=65520

*(p+0)+1=65516    *(p+1)+1=65522

*(*(p+0)+1)=2        *(*(p+1)+1)=5

    It can be illustrated as

Example:

         Write a program to add two 2*3 matrixes using pointer.

void main()

 {

     int (*a)[3],(*b)[3],*(sum)[3],i,j;

     clrscr();

     printf("Enter first matrix:\n");

     for(i=0;i<2;i++)

            for(j=0;j<3;j++)

               scanf("%d",*(a+i)+j);

      printf("Enter second Matrix:\n");

     for(i=0;i<2;i++)

            for(j=0;j<3;j++)

               scanf("%d",*(b+i)+j);

    printf("\nThe sum matrix is:\n");

     for(i=0;i<2;i++)

       {

            for(j=0;j<3;j++)

              {

*(x+2)+1)

               *(*(sum+i)+j)= *(*(a+i)+j)+ *(*(b+i)+j);

               printf("\t%d",*(*(sum+i)+j));

              }

       printf("\n");

      }

     getch();

 }