Arrays and Pointers

Tags: #◇CCPROG2 #◇C Programming #◇Programming #◇Computer Science #◇Data Structures #◇Data Types #◇Structured Programming #◇Memory Management

◇Overview

In expressions, an array name decays to a pointer to its first element.

◇Key Concepts

In expressions

◇Details / Theory

In expressions, an array name decays to a pointer to its first element. arrayName is equivalent to &arrayName[0].

Access using pointers:

int arr[3] = {10, 20, 30};
int *ptr = arr;

printf("%d\n", arr[1]);      // 20
printf("%d\n", *(arr + 1));  // 20
printf("%d\n", ptr[1]);      // 20
printf("%d\n", *(ptr + 1));  // 20

Personal Note: Understand array-pointer relationships for memory handling.

◇Common Pitfalls

Thinking an array is a pointer — an array name decays to a pointer in expressions, but sizeof(arr) still returns the full array size in its declaring scope Confusing arr[i] with *(arr + i) in terms of behavior — they are equivalent, but pointer arithmetic on the wrong type (e.g., char* vs int*) causes incorrect offsets Incrementing the array name directly (arr++) — array names are not modifiable lvalues; only pointer variables can be incremented Forgetting that pointer arithmetic scales by sizeof(element_type) — arr + 1 moves by one element, not one byte

◇Summary

TL;DR — An array name decays to a pointer to its first element in most expressions. arr[i] is equivalent to *(arr + i). Key distinction: arrays have a fixed address (cannot be reassigned), while pointers are variables that can be reassigned and incremented.

◇Links

Related: Source / Reference:

◇References & Navigation

• Previous Topic: ◇Arrays and Functions
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• Related Notes: ◇Memory Allocation, ◇Arrays