C Programming

Pointer vs Array

Most of the time, pointer and array accesses can be treated as acting the same, the major exceptions being:

1) the sizeof operator
o sizeof(array) returns the amount of memory used by all elements in array
o sizeof(pointer) only returns the amount of memory used by the pointer variable itself

2) the & operator
o &array is an alias for &array[0] and returns the address of the first element in array
o &pointer returns the address of pointer

3) a string literal initialization of a character array
o char array[] = “abc” sets the first four elements in array to ‘a’, ‘b’, ‘c’, and ‘\0?
o char *pointer = “abc” sets pointer to the address of the “abc” string (which may be stored in read-only memory and thus unchangeable)

4) Pointer variable can be assigned a value whereas array variable cannot be.

int a[10];
int p; 
p=a; /legal/
a=p; /illegal/ 
5) Arithmetic on pointer variable is allowed.
p++; /Legal/
a++; /illegal*/ 

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