How Do Arrays and Pointers Differ in C and C ?

Arrays and Pointers in C and C

In C and C , arrays and pointers are distinct entities with different implementations.

Arrays

Arrays are data structures that store a fixed-size collection of elements of the same type. They are identified by a base address and a number of elements.

Pointers

Pointers are variables that store the address of another variable. They allow indirect access to data, enabling the modification of values through their address.

Relationship Between Arrays and Pointers

In both C and C , arrays are implicitly converted to pointers when used in expressions. Specifically, the expression arr[i] is equivalent to *(arr i) where arr is the array base address and i is the subscript.

This conversion allows pointers to operate on arrays as if they were pointers to the first element of the array. However, this does not mean that arrays are the same as pointers.

Key Differences

• Type: Arrays are not pointers; they are a different type altogether.
• Size: Arrays have a fixed size determined at compile time, while pointers can point to data of any size.
• Arithmetic: Pointer arithmetic operates on addresses, while array subscripting operates on offsets from the base address.
• Automatic Array Decay: Array expressions are automatically converted to pointers when used in expressions, while pointers do not automatically convert to arrays.

Example

Consider the following declaration in C:

int arr[10];
int *ptr = arr;

• arr is an array of 10 integers, stored contiguously in memory.
• ptr is a pointer that points to the first element of arr.

In this example, the expression arr[i] will be converted to ptr and the expression ptr will be equivalent to arr[i]. However, the types of arr and ptr remain distinct.

Conclusion

Arrays and pointers in C and C are related concepts due to array expression decay, but they are fundamentally different data structures with different implementations and behaviors.

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