# Pointers and Arrays

**Pointers to values**

//value(of type int) stored in a memory locationint value;//avalue: pointer to a value of type int //avalue: address of a memory location containing a value of type intint* avalue;// Extracting the address of valueavalue = &value;

// Extracting value from address/pointerint val = *avalue;

**1-dimensional arrays**

// One dimensional arrayAof size 6int A[6];

**A**: Value of **&A[0]** OR pointer to the value at 0-th index

**A[i]**: Value stored in the i-th index, where 0 <= i < 6

**(A+i)**: Value of **&A[i]** OR pointer to the data at i-th index

***(A+i)**: Same as **A[i]**

**Multi-dimensional arrays**

Once the pointer arithmetic is clear in the context of one-dimensional arrays, we can now easily extend the logic to the pointer arithmetic in multi-dimensional arrays.

//Ais a 3-dimensional array with the dimensions 4, 3 and 2, and having values of type intint A[4][3][2];

**A**: Value of **&A[0]**

**A[i]**: Value of **&A[i][0]**, where 0 <= i < 4

**A[i][j]**: Value of **&A[i][j][0]**, where 0 <= i < 4, 0 <= j < 3

**A+i**: Same as **&A[i]**

***(A+i)**: Same as **A[i]** OR value of **&A[i][0]**

***(A+i)+j**: Value of **&A[i][j]**

***(*(A+i)+j)**: Same as **A[i][j]** OR value of **&A[i][j][0]**

***(*(A+i)+j)+k**: Value of **&A[i][j][k]**, where 0 <= i < 4, 0 <= j < 3, 0 <= k < 2

***(*(*(A+i)+j)+k)**: Same as **A[i][j][k]**

**Generalization**

int A[i_1][i_2]...[i_n];

Value of **A[i_1][i_2]…[i_k]** = **&A[i_1][i_2]…[i_k][0]**

**Difference between A[k] and *pA**

int A[50];

- Array A allocated for 50 elements, each of which is of type int
- Assignment A = 25 is not allowed

int *pA;

- a pointer to an int
- pA can be changed at any time