The major difference between a pointer and an array in C

In C, an array is a fixed-size collection of elements of the same type. A pointer is a variable that stores the memory address of a value or another variable. There are several key differences between pointers and arrays in C:

1. Array elements are stored contiguously in memory, while a pointer can point to any location in memory.

2. The size of an array is fixed, while the size of a pointer is determined by the system architecture (e.g. 32 bits or 64 bits).

3. An array name refers to the address of the first element in the array, but a pointer stores the address of a specific location in memory.

4. An array can be initialized with a list of values at the time of declaration, but a pointer must be assigned the address of an existing value or variable.

5. An array can be accessed using the subscript operator (e.g. arr[i]), while a pointer must be dereferenced using the indirection operator (e.g. *ptr) to access the value it points to.

Here is an example of declaring and initializing an array and a pointer in C:

int arr[5] = {1, 2, 3, 4, 5};  // array of 5 integers
int *ptr = &arr[2];  // pointer to the 3rd element in the array

You can access the elements of the array using the subscript operator:

int a = arr[0];  // a is 1
int b = arr[2];  // b is 3

You can access the value pointed to by the pointer using the indirection operator:

int c = *ptr;  // c is 3

You can also use the pointer arithmetic to access other elements in the array:

Copy codeint d = *(ptr + 1);  // d is 4
int e = *(ptr - 1);  // e is 2

It's important to note that pointers and arrays are closely related in C and can often be used interchangeably. For example, you can use an array name as a pointer to the first element in the array, and you can use a pointer as an array by using the subscript operator. However, it's generally a good idea to be explicit about whether you are using a pointer or an array to avoid confusion.