C Language Arrays Setting values in arrays
Example
Accessing array values is generally done through square brackets:
int val;
int array[10];
/* Setting the value of the fifth element to 5: */
array[4] = 5;
/* The above is equal to: */
*(array + 4) = 5;
/* Reading the value of the fifth element: */
val = array[4];
As a side effect of the operands to the + operator being exchangeable (--> commutative law) the following is equivalent:
*(array + 4) = 5;
*(4 + array) = 5;
so as well the next statements are equivalent:
array[4] = 5;
4[array] = 5; /* Weird but valid C ... */
and those two as well:
val = array[4];
val = 4[array]; /* Weird but valid C ... */
C doesn't perform any boundary checks, accessing contents outside of the declared array is undefined (Accessing memory beyond allocated chunk ):
int val;
int array[10];
array[4] = 5; /* ok */
val = array[4]; /* ok */
array[19] = 20; /* undefined behavior */
val = array[15]; /* undefined behavior */
