Chapter 7 Arrays

Array

An array is a collection of similar elements

one variable ⇒ capable of storing multiple values

Syntax

The syntax of declaring an array looks like this.

Int marks[90]; ⇒ Integer array

char name[20]; ⇒ character array or strong

float percentile[90]; ⇒ float array

The values can now be assigned to marks array like this :

marks [0] ⇒33;

marks [1] ⇒12;

NOTE; It is very important to note that the array index starts with 0

marks → 7,6,21,3,91,3,.,.,.,88,89

           0 1  2 3 4 5 . . . 88  89

                  Total = 90 elements

Accessing elements

Elements of an array can be accessed using ;

scanf(”%d”,&marks[0]); ⇒ Input first value

printf(”%d”,marks[0]); ⇒ Output first value of the array

Initialization of an array

There are many other ways in which an array can be initialized.

int cgpa [3] = {9,8,8} ⇒ Array can be initialized while declaration

float marks[] = {33,40}

Arrays in memory

Consider this array;

int arr [3]={1,2,3} ⇒ 1 integer =4bytes

This will reserve 4*3 =12 bytes in memory

1 2 3 ⇒ arr in memory

62302 62306 62310

Pointer Arithmetic

A pointer can be incremented to point to the next memory location of that type.

Consider this example

int i =32;

int *a =&i; ⇒ a=87994

a++;

Char a=’A’

char *b =&a; ⇒ b=87994

b++; ⇒ now b =87995

Following operations can be performed on a pointers:

1. Addition of number to a pointer
2. subtraction of a number from a pointer
3. subtraction of one pointer from another
4. comparison of two pointer variables

5. 

   
   
   

Accessing arrays using pointers

Consider this array

                7    9    2    8    1

index 0 1 2 3 4

                ptr

If ptr points to index 0, ptr++ will point to index 1 & so on….

This way we can have an integer pointer pointing to first element of the array like this;

int * ptr = & arr[0]; → or simply arr

ptr++;

*ptr ⇒ will have 9 as its value

Passing arrays to functions

Arrays can be passed to the functions like this

printArray(arr,n); ⇒ function call

void printArray (int*i, int n); ⇒ functional prototype

or

void printArray (inti[], int n);

Multidimensional Arrays

An array can be of 2 dimension/3 dimension/ n dimensions

A 2 dimensional array can be defined as;

int arr [3] [2] = { {1,4}

                 `{7,9}`

                 `{11,22} };`

we can access the elements of this array as arr [0] [0] , arr [0] [1] & so on…

2-D arrays in memory

A 2d array like a1-d array is stored in contiguous memory blocks this

arr[0] arr[0] [1] ……..

1 4 7 9 11 22

87224 87228 ……..