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    Arrays and Pointers

    Arrays and pointers are different but connected.

    Example:

    int A[5] = {2,4,5,8,1};

    Address and value mapping

    Address:

    &A[i] == (A+i)

    Value:

    A[i] == *(A+i)

    So [] is syntactic sugar.

    Arrays and Pointers Diagram

    Arrays and Pointers

    Demonstrates how arrays and pointers are related, including base address concept, memory layout of elements, and pointer arithmetic like A[i] == *(A+i)

    Why A++ is invalid?

    Array name is constant base address (non-modifiable lvalue).

    A++; // ❌

    But pointer is modifiable:

    int *p = A;
p++; // ✅

    sizeof array vs pointer

    sizeof(A)  // full size
sizeof(p)  // pointer size

    Array Decay (Passing array to function)

    When passed to function, array becomes pointer.

    int sum(int A[], int n) { ... }

    Inside function:

    sizeof(A) == sizeof(int*)

    Character arrays and strings

    C strings must be null terminated.

    char s[] = "Hello"; // includes \0

    strlen vs sizeof

    strlen(s) // 5
sizeof(s) // 6

    Array vs pointer for string literal

    char c1[] = "Hello"; // modifiable copy
char *c2 = "Hello";  // read-only literal

    c2[0]='A' is undefined behavior.

    Pointer to array (array pointer)

    Normal pointer:

    int *p = A;

    Pointer to full array:

    int (*pa)[5] = &A;

    Pointer arithmetic: