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Sunday, 6 May 2012

Array Declaration

Array declaration is similar to the ordinary variable declaration except that the array name will have information on number of elements it can hold.

Syntax:
     data_type array_name[subscript];
     data_type         - specifies the type of data that the array will hold
     array_name       - name of the array
     subscript           - specifies the number of elements it can accommodate

Example:
int arr[10];  //arr is an array of 10 integers


Example C program on array declaration

#include <stdio.h> 
  int main() {
        int i, num[10], *ptr;  // declaration for integer array num
        for (i = 0; i < 10; i++) {
                num[i] = i;  // assigning values to array elements
        }
        // assigning pointer ptr to the first element of the array
        ptr = num;
        printf("ptr: 0x%x  num:0x%x  &num[0]: 0x%x\n", ptr, num, &num[0]);
        for (i = 0; i < 10; i++) {
                // *(ptr+i) is equivalent to num[i]
                printf("num[%d]: %d\t*(ptr + %d): %d\n",
                                i, num[i], i, *(ptr + i));
        }
        return 0;
  }


  Output:
  jp@jp-VirtualBox:~/$ ./a.out
  ptr: 0xbf8ecd70  num:0xbf8ecd70  &num[0]: 0xbf8ecd70
  num[0]: 0      *(ptr + 0): 0
  num[1]: 1      *(ptr + 1): 1
  num[2]: 2      *(ptr + 2): 2
  num[3]: 3      *(ptr + 3): 3
  num[4]: 4      *(ptr + 4): 4
  num[5]: 5      *(ptr + 5): 5
  num[6]: 6      *(ptr + 6): 6
  num[7]: 7      *(ptr + 7): 7
  num[8]: 8      *(ptr + 8): 8
  num[9]: 9      *(ptr + 9): 9



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