Two-Dimensional Arrays

        Example:
        1 int scores[4][140];   /* 4 classes, up to 140 students each */
        2 int row, col, x, y;

        3 for (row = 0; row < 4; row++)
        4     for (col = 0; col < 140; col++)
        5         score[row][col] = 0;

        6 x = 2; y = 45;
        7 scores[3][100] = 99;
        8 scores[x][y] = 25;            /* same as: scores[2][45] = 25; */
        9 scores[x+1][y+x] = 34;        /* same as: scores[3][47] = 34; */
       10 printf("enter a value: ");
       11 scanf("%d", &scores[3][100]);

Two-D Arrays and Functions:

       #include <stdio.h>

        void init(int list[][140], int rows);
        int main(void)
        {
            int scores[4][140];

            init(scores,4);
            /* not shown: rest of program */
            return(0);
        }

        void init(int list[][140], int rows)
        {
            int i, j;

            for (i = 0; i < rows; i++)
                for (j = 0; j < 140; j++)
                    list[i][j] = 0;
        }

Pointers and Functions
Incorrect version of swap:
        int main (void)
        {
            int x,y;

            x = 3; y = 100;
            swap(x,y);
            ...
            return(0);
        }

        void swap(int x, int y)
        {
            int temp;
            
            temp = x;
            x = y;
            y = temp;
        }
Correct version of swap:

        int main (void)
        {
            int x,y;

            x = 3;
            y = 100;
            swap(&x,&y);
            ...
            return(0);
        }
         
        /* new version of swap, with pointer parameters */
        void swap(int *p1, int *p2)
        {
            int temp;
            
            temp = *p1;
            *p1 = *p2;
            *p2 = temp;
        }

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Using Pointers for "Multiple Return Values"

  #include <stdio.h>
  void sumProduct(int num1, int num2, int *sump, int *productp);

  int main (void)
  {
    int num1, num2, sum, product;

    printf("enter 2 values:");
    scanf("%d %d", &num1, &num2);

    sumProduct(num1, num2, &sum, &product);
    printf("sum= %d product = %d\n", sum, product);  
    return(0);
   } 

  void sumProduct(int n1, int n2, int *sump, int *productp)
  {
    *sump = n1 + n2;
    *productp = n1 * n2;
  }