wk 16 l111111

8/6/2019 Wk 16 L111111

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WEEK # 16

LECTURE 1

³Pointers & Functions´

8/6/2019 Wk 16 L111111


Pointers and Arrays (Revision)

#include<iostream.h>

void main()

{

int a[3]={4,7,11};

cout<<&a[0]<<endl;

cout<<a<<endl<<endl;;

cout<<&a[1]<<endl;

cout<<(a+1)<<endl<<endl;

cout<<&a[2]<<endl;

cout<<(a+2)<<endl<<endl;

}

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void main()

{

int a[3]={4,7,11};

cout<<a[0]<<endl;

cout<<*a<<endl<<endl;;

cout<<a[1]<<endl;

cout<<*(a+1)<<endl<<endl;

cout<<a[2]<<endl;

cout<<*(a+2)<<endl<<endl;

}

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void main()

{

int a[3]={4,7,11};

int *p;p=a;

cout<<*(p+0)<<endl;

cout<<p[0]<<endl<<endl;;

cout<<*(p+1)<<endl;cout<<p[1]<<endl<<endl;

cout<<*(p+2)<<endl;

cout<<p[2]<<endl<<endl;

}

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void main()

{

int a[3]={4,7,11};

int *p;p=a;

cout<<(p+0)<<endl;

cout<<&p[0]<<endl<<endl;;

cout<<(p+1)<<endl;cout<<&p[1]<<endl<<endl;

cout<<(p+2)<<endl;

cout<<&p[2]<<endl<<endl;

}

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void main()

{

int a[3]={4,7,11};

int *p;

p=a;

cout<<&a[0]<<endl;

cout<<p<<endl<<endl;;

p++;

cout<<&a[1]<<endl;

cout<<p<<endl<<endl;

}

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void main()

{

int a[3]={4,7,11};

cout<<&a[0]<<endl;

cout<<a<<endl<<endl;;

a++;cout<<&a[1]<<endl;

cout<<a<<endl<<endl;

}

Error Address of Array

are fixed and cant be

changed like Pointer

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PASSING ARGUMENT TOFUNCTIONS

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Functions of Factorial

#include <iostream.h>

int factorial(int num);

void main()

{int x;

cout<<"Enter number to find Factorial : ";

cin>>x;

cout<<"Answer is "<<factorial(x);

cout<<endl<<endl;

}

int factorial(int num)

{

int product=1;

for(int i=1;i<=num;i++)

{product=product*i;

}

return product;

}

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Passing Argument To

Functions

There are two ways that a language can pass an argument to a function.

The first is call-by-value.

� This method copies the value of an argument into the parameter of the

function. Therefore, changes made to the parameter of the subroutine

have no effect on the argument used to call it.

Second is Call-by-reference

� In this method, the address of an argument (not its value) is copied intothe parameter. Inside the function, this address is used to access the

actual argument specified in the call. This means that changes made to

the parameter will affect the argument used to call the function

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Call-by-Value


double reciprocal(double x);

void main()

{

double t=10;

cout<<"Reciprocol of 10 is "<<reciprocal(t)<<endl;

cout<<"Value of t is "<<t<<endl;

}

double reciprocal(double x)

{

x=1/x;

return x;}

The only thing modified is the

local variable x. The local

variable t used as an argument

will still have the value 10 and

is unaffected by the operations

inside the function.

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Call-by-Value



void main()

{

double x=10;

cout<<"Reciprocol of 10 is "<<reciprocal(x)<<endl;

cout<<"Value of x is "<<x<<endl;

}


{

x=1/x;

return x;}

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Call-by-Reference

It is possible to manually create a call-by-reference by

passing the address of an argument (that is, a pointer) to a

function.

Pointers are passed to functions just like any other values. Of

course, it is necessary to declare the parameters as pointer

types.

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Call-by-Reference


void fun(int *j);

void main()

{

int i;int *p;

p=&i;

fun(p);

cout<<i<<endl; }

void fun(int *j)

{

*j=100;

}

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Call-by-Reference


void fun(int *j);

void main()

{

int i=10;int *p;

p=&i;

cout<<i<<endl;

fun(p);

cout<<i<<endl; }

void fun(int *j)

{

*j=100;}

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Call-by-Reference


void fun(int *j);

void main()

{

int i=10;

cout<<i<<endl;

fun(&i);

cout<<i<<endl; }

void fun(int *j)

{

*j=100;

}

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Call-by-Reference


void fun(int *j);

void main()

{

int i=10;

cout<<i<<endl;

fun(&i);

cout<<i<<endl; }

void fun(int *i)

{

*i=100;

}

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Call-by-Value



void main()

{

double t=10;

cout<<"Reciprocol of 10 is "<<reciprocal(t)<<endl;

cout<<"Value of t is "<<t<<endl;

}


{

x=1/x;

return x;}

The only thing modified is the

local variable x. The local

variable t used as an argument

will still have the value 10 and

is unaffected by the operations

inside the function.

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Call-by-Reference


void reciprocal(double *x);

void main()

{

double t=10;

reciprocal(&t);

cout<<"Value of t is "<<t<<endl;}

void reciprocal(double *x)

{

*x=1/(*x);

}

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Factorial (Call-by-Value)


int factorial(int num);

void main()

{int x;


cin>>x;

cout<<"Answer is "<<factorial(x);

cout<<endl<<endl;

}

int factorial(int num)

{

int product=1;

for(int i=1;i<=num;i++)

{product=product*i;

}

return product;

}

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Factorial (Call-by-Reference)


void factorial(int *num);

void main()

{int x;


cin>>x;

factorial(&x);cout<<"Answer is "<<x;

cout<<endl<<endl;

}

void factorial(int *num)

{

int product=1;

for(int i=1;i<=(*num);i++)

{product=product*i;

}

*num=product;

}

wk 16 l111111

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