c++ ppt2

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Integer array of 4 elements

1000 1002 1004 1006

ARRAYSAn array is a collection of variables ofsimilardatatype.

A specific element in an array is accessed by an index.

Arrays may have from one to several dimensions.

In C/C++, all arrays consist of contiguous memorylocations.

The lowest address corresponds to the first elementand the highest address to the last element.

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Single dimension Arrays The general form declaring an array is

[size];

Eg:

int marks[5];

The values are accessed by the indexes.

Eg:

marks[0]=90;marks[1]=95;

marks[2]=98;

marks[3]=85;

marks[4]=80;

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Example/* Program to use arrays */

#include

#include

void main(){

int arr[5]; //declaring array variable of size 5

clrscr();

for(int i=0;i

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Memory mapping

arr[0] arr[1] arr[2] arr[3] arr[4]

1 2 3 4 5

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Two dimensional Array C/C++ supports multidimensional arrays.

The simplest form of the multidimensional array is the

two-dimensional array. The declaration syntax is

[size][size];

LeftIndex Right Index

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Example/* Program for two dimensional array */

#include

#include

void main()

{ int t, i, num[3][4];

for(t=0; t

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Multi dimensional Array

C/C++ allows arrays of more than two dimensions.

The exact limit, if any, is determined by the compiler.

The general form of a multidimensional arraydeclaration is

[size1][size2][size3][sizen];

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Example/* Matrix Addition */#include

#include

void main()

{

int mat1[3][3];

int mat2[3][3];

int i,j;

cout

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for(i=0;imat2[i][j];

}

int mat[3][3],k,l;

cout

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Array Initialization C/C++ allows the initialization of arrays at the time of

their declaration.

Syntax

[size1]. . .[sizeN] = {value_list};

Eg:

int i[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

Thevalue_list is a comma-separated list of values whose

type is compatible with data type.

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Array InitializationWe can initialize the multi dimensional arrays also.

Eg:int sqr[3][2] = {1,1,2,4,3,9};

Another way

int sqr[3][2] = {{1,1},{2,4},{3,9}};

This is called Sub aggregate Grouping

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Pointers

Pointers provide the means by which functions can

modify their calling arguments.

Pointers support dynamic allocation.

Pointers can improve the efficiency of certain routines.

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What are pointers?

Apointeris a variable that holds a memory address.

This address is the location of another object (typicallyanother variable) in memory.

Memory Address

1000

1001

1002

1003

1004

Variable in memory

1003

.

.

.Memory

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Declaration of Pointer

Syntax:

*;

The base type of the pointer defines what type ofvariables the pointer can point to.

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Pointer Operators There are two special pointer operators: *and &. The &(Referencing Operator) is a unary operator that

returns the memoryaddress of its operand.

m=&count; * (De-referencing Operator) is the complement of&.

It is a unary operator that returns thevalue located atthe address that follows.

q=*m;

count m q

2000

1002

1002 2000

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Example/* Program for pointers */

#include

#include

void main()

{

clrscr();

int a,*p;

couta;

p=&a;

cout

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The void type of pointer is a special type of pointer.

In C++, void represents the absence of type.

So void pointers are pointers that point to a valuethat has no type.

Void Pointers

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int a;

int v1;

void *ptr;

a=100;

ptr=&a;

v1=*(int*)ptr; //defining the type

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Example-1

int a,v1;char b,v2;

void *ptr;

a=100;ptr=&a;

v1=*(int*)ptr; //now it s pointing to integer

cout

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Example-2

#include#include

void display(int x,void *y)

{

int a;

char b;if(x==1)

{

a=*(int*)y;

cout

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void main(){

int s1;

char s2;

void *ptr1;

clrscr();s1=300;

ptr1=&s1;

display(1,ptr1); //function call with int value

s2='J';

ptr1=&s2;display(2,ptr1);//function call with char value

getch();

}

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Pointer ExpressionAssignment

int var,*p1,*p2;

p1=&var;

p2=p1;

In this pointers p1 and p2pointsto the samevariablevar.

Arithmeticint var,*p;

p=&var;

p++; // or p--;

In this pointer moves to the next memory location

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Pointer with Array Syntax:

int *ptr;

int sample[5];ptr=sample;

It can also use & operator to specify the address of

1st element.ptr=&sample;

Note: Pointers can be arrayed like any other data type.

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Multiple Indirection Multipleindirection or pointerstopointers is a pointer

point to another pointer that points to the target value.

Eg:

float bal;

float *balance,**newbalance;

balance=&bal;

newbalance=&balance;

Multiple indirection can be carried on to whateverextent required.

More than a pointer to a pointer is rarely needed.

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Functions

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Function

Function is basic requirement of modularprogramming.

The process of dividing a large program into small subprograms and manipulating them independently isknown as modular programming.

A function is a named, independent, block ofstatements that perform well defined, specific taskand may return a value.

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Types of Function Pre-defined functions User defined functions

Pre-defined functions

The functions, which has special type ofmeaning which isalreadydefined and stored, is called built-in functions orpre-defined functions.

Eg:

int a=4;x=pow(a,2);

User defined functions

Can be createdbytheuseror programmer for performing

specific task.

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Any C++ program contains at least one function.

If a program contains only one function, it must be main( ). If a C++ program contains more than one function, then one (and

only one) of these functions must be main( ), because program

execution always begins with main( ).

There is no limit on the number of functions that might bepresent in a C++ program.

Each function in a program is called in the sequence specified bythe function calls in main( ).

After each function has done its thing, control returns to main().

When main( ) runs out of function calls, the program ends.

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Structure of Function(arg 1,

arg 2,,arg n)

{

declaration part;

statements;

return;}

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Exampleint sum(int x,int y)

{

int result;

result = x + y;

return (result);

}

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Properties

Every function has a uniquename. This name is used tocall the function from main() function.

A function can be calledfrom within anotherfunction.

A function is independent and it can perform its taskwithout intervention from or interfering with other partsof the program.

A function returns a value to the calling program. This isoptional and depends upon the task.

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Example#include

void main()

{

cout

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brazil()

{

cout

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Rules A function gets called when the function name is followed

by a semicolon.main()

{

func();

}

A function is defined when function name is followed by apair of braces in which one or more statements may bepresent.

func(){

statement 1 ;

statement 2 ;

statement 3 ;

}

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Rules

A function can be called any number of times.

main()

{display() ;

display() ;

}

display()

{

cout

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Rules

The order in which the functions are defined in a programand the order in which they get called need not necessarilybe same.main()

{

display1() ;display2() ;}

display2(){

cout

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Rules

A function can call itself. This is known as Recursion.

int fact(int n)

{

if(n==0)

return(1);

return(n*fact(n-1));

}Note: This function is known as RecursiveFunction.

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Parts of the Function

Function prototype declaration

Definition of a function

Function call

Actual and formal arguments

The return statement

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Parts of the Function Function prototype:

It helps the compiler to check the return and argumenttypes of the function.

Function prototype declaration consists of Function return type

Name

Arguments list

Ex:void show(void);

int sum(int,int);

float sum(float,int);

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Function Definition:

The block of statement followed by functiondeclarator is called as function definition.

The declarator and function prototypedeclaration should match each other.

Function Call:A function is called by its name followed by

arguments list enclosed in parenthesis andterminated by semi-colon.

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Parts of the FunctionActual and formal arguments:

The arguments declared in calling function arecalled actual arguments.

The arguments declared in function declaratorare called formal arguments.

The return statement:

The return statement is used to return the value tocaller function.

The return statement returns only one value at atime.

Syntax : return (variable name);

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void main()

{

int sum(int,int);

int a=10,b=20,c;

c=sum(a,b);

}

int sum(int x,int y)

{

return(x+y);

}

Function Prototype

Function call

Actual arguments

Function declarator

Function definition

Return statement

Formal arguments


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Types of Function

A function may belong to any one of the followingcategories:

1. Functions with no arguments and no return values.

2. Functions with arguments and no return values.

3. Functions with arguments and return values.

4. Function with no arguments and return values.

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Functions with no arguments and no return values This is the simplest function ,it does not receive any

arguments from the called function and does notreturn any value from calling function.

Types of Function

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Functions with arguments and no return values This function receives arguments from calling

function and does not return value to the callingfunction.

Types of Function

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Functions with arguments and return values This function receives arguments from calling

function and returns the computed value back to thecalling function.

Types of Function

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Functions with no arguments and return values

Types of Function

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Function Call

There are two ways to call a function.

1. Call byValue

2. Call byReference

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