Pointer vs array in C

The pointers and arrays are closely related concepts, but they have distinct differences and serve different purposes. Understanding these differences is essential for writing efficient and correct C programs. Here are some key points to compare pointers and arrays in C:

1. Declaration and Initialization:

• Arrays are collections of elements of the same data type. They are declared and initialized as follows:
  c int arr[5] = {1, 2, 3, 4, 5};
• Pointers, on the other hand, are variables that store memory addresses. They can be initialized with the address of an existing variable or dynamically allocated memory:
  c int x = 42; int *ptr = &x; // Initialize 'ptr' with the address of 'x'

1. Memory Representation:

• Arrays allocate contiguous memory locations to store elements. The array name itself acts as a pointer to the first element of the array.
• Pointers are variables that store memory addresses and can point to a single value or a sequence of values. They are not necessarily allocated in contiguous memory locations.

1. Size:

• The size of an array is fixed at the time of declaration and cannot be changed during the program’s execution.
• Pointers can be used to dynamically allocate and deallocate memory, so the size of the data they point to can be changed at runtime using functions like malloc and free.

1. Accessing Elements:

• Array elements are accessed using the array subscript notation (arr[index]).
• Pointer arithmetic can be used to access elements of an array using pointers (ptr + index or *(ptr + index)). In fact, arrays are often accessed using pointers.

1. Passing to Functions:

• When you pass an array to a function, you are actually passing a pointer to the first element of the array. Changes made to the array inside the function affect the original array.
• Pointers can be passed to functions just like any other variable. Changes made to the pointed-to value inside the function do not affect the original pointer.

1. Sizeof Operator:

• The sizeof operator returns the size of an array in bytes.
• When used with a pointer, sizeof returns the size of the pointer itself, not the size of the data it points to.

1. String Handling:

• Strings in C are typically represented as character arrays (char[]) or character pointers (char*). String literals are represented as arrays of characters.
• Character pointers are often used to manipulate strings in C.

In summary, while arrays and pointers are related, they have distinct characteristics and purposes in C. Arrays provide a convenient way to group elements of the same type together, while pointers are more flexible and versatile, allowing dynamic memory allocation and manipulation of data in memory. Understanding when to use each is crucial for writing efficient and correct C code.