Programming language C & C++ Function

1. Function in
Programming Language
(C & C++)
Guided by-
All Teachers
Presented by –
Rahul Sahu
B.Sc.- 2nd Year (CS)

2. Definition:-
A large program can be divided into a series of
individual related programs called “Modules”.
These Modules are called “Function”.
The function can be classified into two
categories –
i. In-Built Function
ii. User Defined Function

3. Defining a function: -
return type_function name(Argument)
{
----------------------------
Body of function
----------------------------
}
i. Return type
ii. Function name
iii. Argument
iv. Body of function

4. Element of User Defined
Function:-
Three elements of User Defined Function –
i. Function Declaration
ii. Function Definition
iii. Function Calling

5. Function Declaration:-
Function are like variables. As variables
are declared before they are used, we
normally declare the function before they
are defined and end with semicolon. This
is called Function Declaration.
Example:- int add();
float per();

6. Function Definition:-
The program module that is written to
achieve a specific task is called Function
Definition .
Example:-
add() add()
{ {
int a,b,c; int a,b,c;
scanf(“%d %d”,&a,&b); cin>>a>>b;
c=a+b; c=a+b;
printf(“n %d”,&c); cout<<c;
} }

7. Function Calling:-
We know that execution always start from
main function. If we want to use the
function that we have just discussed, it
has to be invoke. This is called Function
Call.
Example:- void main( )
{
add( );
}

8. Example:-
#include<stdio.h> #include<iostream.h>
#include<conio.h> #include<conio.h>
int add( int a, int b) int add(int a, int b)
{ {
int c; int c;
c=a+b ; c=a+b;
printf(“n %d”,c); cout<<“addition of no.=“<<c;
} }
void main ( ) void main( )
{ {
add(2,3 ); add(3,4);
} }
Output:- 5 Output:- addition of no. 7

9. Argument or Parameter:-
The Argument or Parameter can be classified into
two categories –
i. Formal Argument
Example:- int add( int ,int)
ii. Actual Argument
Example:- add(4,5)

10. Passing Argument to
function:-
Two type of Passing Argument to function –
i. Call By Value
ii. Call By Reference

11. Call By Value:-
When a function is called with actual
parameters, the values of actual parameters
are copied into formal parameters. If the
values of the formal parameter change in
the function, the values of the actual
parameters are not changed. This way of
passing, parameters is called “Pass by Value”
or “Call by Value”.

12. Call By Reference:-
In call by reference, a function is called with
addresses of actual parameters. In the
function header, the formal parameters
receive the addresses of actual parameters.
Now, the formal parameters do not contain
values, instead they contain addresses. Any
variable if it contain an address, it is called a
pointer variable. Using pointer variables, the
values of the actual parameters can be
changed. This way of passing parameters is
called “Pass by Reference” or “Call by
Reference”.

13. Thank You