Arrays Revisited

Arrays are consecutive memory blocks

C array indices start with 0 and go to n - 1

0 1 2 ... n - 1

Any defined data type (user or built-in) can be made into an array

A C string is only an zero terminated array of characters

Multi-dimensional arrays are possible

      int numbers2d [10][10];
      int numbers3d [10][10][10];

Two dimensional arrays are, in reality, one dimensional arrays where each element is an array itself. Elements in two dimensional arrays are stored by rows so the rightmost subscript, the column, varies fastest

Since C internally treats arrays as one dimensional memory blocks then the array dimensions must be specified when an array is passed into a function

Example:

     #include <stdio.h>
     
     #define ROWS  2
     #define COLS  3
     
     /*
      * Program to show various array capabilities
      */
     int main ( void ) {
       /* define a static array */
       int days [] = { 1, 2, 3, 4, 5 };
     
       /* define a static array of characters (aka a string) */
       char string [] = "this is a string";
     
       /* two dimensional array using definitions from above */
       float numbers [ROWS][COLS];
       int row, col;
     
       /* remember - the sizeof operator includes the terminator */
       printf ( "Length of the string (including the terminator): %d\n",
                sizeof ( string ) );
     
       /* loop over the array printing all values */
       for ( row = 0; row < ROWS; row++ ) {
         for ( col = 0; col < COLS; col++ ) {
           numbers [row][col] = (float) row * col;
           printf ( "numbers [%d][%d] = %5.2f\n", row, col, numbers [row][col] );
         }
       }
     
       return ( 0 );
     }

Output:

Length of the string (including the terminator): 17
numbers [0][0] =  0.00
numbers [0][1] =  0.00
numbers [0][2] =  0.00
numbers [1][0] =  0.00
numbers [1][1] =  1.00
numbers [1][2] =  2.00