1-D Arrays

C array

• At declaration, only the number of elements wanted is given not an index range.
• The index range in C is from 0 to number of elements - 1. No choice.
• The name of the array represents ("holds") the address of the first element in the array.
• You can use both [] notation (like most other languages use) or you may use pointer notation and pointer arithmetic. For the 210 class, you use ONLY [] notation unless I specifically ask you to use pointer notation.
• You may initialize your array at the time of declaration; however, if you don't initialize the array yourself, it is NOT initialized.
• While under certain conditions, the C compiler will give you a default value for the size of the array, this is a very BAD habit to get into. Always, give the size of the array.
• All arrays are passed to functions as in-out parameters. There is no other choice for passing an entire array in C.
• The size of the first dimension is not required in the function prototype or the function header. The declared size of all other dimensions MUST be shown in both the prototype and the function header.

Declaration

   #define  MAX  20

   int numbers[10], vals[MAX], others[MAX*2 + 3];
   float wages[100];
   char letters[24];

   int temp_array[5] = {1, 3, 5, 6, 100};
   int another[100] = {0, 1, 3, 6, 9};
   char grades[] = {'a', 'b', 'c', 'd', 'f'};

Access

   Single element

     numbers[0] = 2;
     letters[23] = 'c';
     wages[135] = 5.15; /* is there a problem here */

   Whole array
     Not possible.  You may only access an array 1 element at a time.
     another = numbers; Is not a valid statement. What this says is give
     the starting address of numbers to the array another.  This will not
     "copy" the values in numbers into the first elements of another.  Don't
     even try it.

Passing arrays to functions.

     pass_whole_array_in_only(numbers, low_index, high_index);
     pass_whole_array_inout_out(numbers, low_index, high_index);

Receiving arrays to functions

     void pass_whole_array_in_only(int array[], int low, int high);

       or void pass_whole_array_in_only(int [], int, int);

       or void pass_whole_array_in_only(int *, int, int);
          /*Don't use the 3rd method unless specifically requested to do so*/


     void pass_whole_array-inout_out(int array[], int low, int high);

       or void pass_whole_array-inout_out(int [], int, int);

       or void pass_whole_array-inout_out(int *, int, int);

Passing part of an array to a function

     min = min4(numbers[1], numbers[2], numbers[3], numbers[4]);
     get_int(&number[1]);  
     fill_array(numbers, 3, 7);  /* purpose is to fill from index 3 to index 7
                                   (5 elements are changed) */

     NOTE: min4() prototype and header have not changed at all
           get_int() prototype and header have not changed at all
           fill_array(int [], int, int) could be used to fill the whole array
                if low = 0 and high = MAX_size - 1