C++ ClassRoom -- Lecture No. 2

OK!

Using functions we can structure our programs in a more modular way, accessing all the potential that structured programming can offer to us in C++ ;).
the structure of functions are like this:
name(parameter1, parameter2, ......) {
....
}
and in brackets you put the type (int, void, float, etc...)
an example is:

void my_func(int a, int b);

So, there
I declare the function as void
and the parameters
as "int".

Code:

type name(parameter1, parameter2, ...) {
//statements
}

the structure:
type: is the data type specifier of the data returned by the function.
name: is the random name that we give ;).
parameters: each parameter consists of a data type specifier followed by an identifier, like any regular variable declaration (for example: int x) and which acts within the function as a regular local variable. They allow to pass arguments to the function when it is called. The different parameters are separated by commas.
statements: is the body...

lets give an example now:

#include<iostream>

using namespace std;

void my_func(int a,int b) {
    int c;
    c=a+b;

    cout<<c<<endl;
}

int main() {
my_func(1,2);
my_func(2,7);
}

here is an example
now we can do the same thing
using return;
but if we use return we can not use
void
so the program will become like this:

#include<iostream>

using namespace std;

int my_func(int a,int b) {
    int c;
    c=a+b;

    cout<<endl;

    return c;
}

int main() {
cout<<my_func(1,2);
cout<<my_func(2,7);
}

Now I will tell about functions by reference.

Some Code:

#include<iostream>

using namespace std;

void my_func(int a,int b) {
   a=5;
   b=6;
}

int main() {
int x=1,y=2;
my_func(x,y);
cout << x << endl;
cout << y << endl;
}


if you run this program
it will print:
1
2
So, the question should be:
why x and y don't take the value 5 and 6?
The answer is:
in functions we can not change the parameters. Instead we use reference operator to change parameters ;).
Reference is used with an & (ampersand) sign.
So, the parameters should be:
"int &a,int &b"
now run this:

#include<iostream>

using namespace std;

void my_func(int &a,int &b) {
   a=5;
   b=6;
}

int main() {
int x=1,y=2;
my_func(x,y);
cout << x << endl;
cout << y << endl;
}


it will print:
5
6

Here I used reference to the parameters but we can do the same thing using pointers to the parameters ;).

So, theoretically "pointers" are same as "reference operators" ;).

Now run this:

#include<iostream>

using namespace std;

void my_func(int *a,int *b) {
   *a=5;
   *b=6;
}

int main() {
int x=1,y=2;
my_func(&x,&y);
cout << x << endl;
cout << y << endl;
}

So, it will print:
5
6

So, both results are same but just the methods are different ;).

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Break Starts
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Break Ends
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Also to make it more advance, we can give the value of the function in a pointer.
For example,

#include<iostream>

using namespace std;

int my_func(int *a,int *b) {
   *a=5;
   *b=6;
}

int main() {
int x=1,y=2;
int (*g)(int *a,int *b);
g=my_func;
g(&x,&y);
cout << x << endl;
cout << y << endl;
}

This is a program
that makes a pointer,
adds into the pointer
the value of the function
and after calling the function
through the pointer,
prints the variables.

-- Lecture Ended --

-- Note --
In the next lesson we can learn about pointers (i.e. hopefully tomorrow) ;).

** The End ;)
** Teacher = "Hepic" ;).
** Class Moderated By "XRahat2011" ;).