Arrays vs. Pointers in C/C : How Do They Differ in Memory Allocation, Size, and Usage?

Understanding the Differences Between int[] and int* in C/C

While arrays and pointers in C and C store data contiguously, their notation (array notation vs. pointer notation) implies significant differences.

Array Declaration

In C and C , arrays are declared using square brackets []:

<code class="c">char c[] = "test";</code>

This statement allocates the string on the stack because arrays in C are just pointers to memory locations.

In contrast, pointers are declared using asterisks (*):

<code class="c">char* c = "test";</code>

This declaration points to a read-only data segment, as the string literal is stored in a read-only memory area.

Array Size

Arrays have a fixed size that is determined at compile-time. The size cannot be modified during program execution. On the other hand, pointers have no intrinsic size information.

Memory Allocation

Arrays are allocated on the stack (unless explicitly specified otherwise), while pointers can be allocated both on the stack and dynamic memory (using malloc or new).

Subscripting

Both arrays and pointers support subscripts. However, for arrays, the subscripting operator [] acts as a synonym for dereferencing the pointer and adding the offset.

Array-to-Pointer Conversion

Arrays can be implicitly converted to pointers to their first element. This conversion is automatic when passing arrays as arguments to functions or when assigning them to pointers.

Pointer-to-Array Conversion

In C, pointers can be explicitly cast to arrays of the same type. However, this conversion is not safe and can lead to undefined behavior.

Recursive Data Structures

Arrays cannot define recursive data structures, as the size of an array is fixed at compile-time. Pointers, on the other hand, can be used to define recursive structures, such as linked lists.

Other Differences

• Pointer arithmetic is allowed, while array arithmetic is not.
• Pointers can be null, while arrays are not.
• Pointers can be dereferenced, while arrays cannot.

These differences highlight the specific use cases for arrays and pointers. By understanding the nuances of each notation, programmers can effectively manage memory and data structures.

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