Arrays in C

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Source: samek-embedded

  • Group of variables of the same type.
  • The variables occupy consecutive memory locations.
  • An array is treated as a pointer (to the beginning of the array). Likewise, every pointer can also be viewed as an array.
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int counter[2] = {0, 0};

counter[0] = 1;
counter[1] = 2;
  • Indexing the array is equivalent to adding the index to the array pointer and getting the value at that address.
  • The value counter[1] is equivalent to *(counter + 1) (pointer arithmetic)

Address arithmetic vs. pointer arithmetic

From the LED example :

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unsigned int LED_RED = (1U << 1);

// address arithmetic
*((unsigned int *)(BASE_ADDRESS + LED_RED_OFFSET)) = LED_RED;

// pointer arithmetic
*(DATA_BITS_R + LED_RED) = LED_RED;
DATA_BITS_R[LED_RED] = LED_RED;

In address arithmetic:

  • address is calculated
  • then cast to a pointer type
  • the pointer value is set via the dereferenced pointer