this ppt give you a basic knowledge about functions in "c" language

1. “ FUNCTION”
By: Rishabh Agrawal

2. Content
 Introduction
 Syntax
 Program
 Types of Functions
 How the Function works?
 Function Prototypes
 Advantages of Function
 Conclusion

3. Introduction
 Function is a name block of statement that are executed
when it is called and performs a specific task.
 C program contain at least one function which is main().
 Basically a function is used to divide a large program of c
in many subprogram.

4. Syntax
For defining:-
return_type function_name(parameter_list)
{
statement(s)
}
For calling:-
function_name(argument_list)

5. Example for Syntax
For defining:-
// function for finding maximum from two no.
int max(int x, int y)
{
if(x>y)
return(x);
else
return(y);
}

6. Cont..
For calling:-
int main()
{
int x,y,m;
x=10;
y=5;
// function calling to get max value
m=max(x,y);
printf(“max value = %d”,m);
}

7. Program
int main()
{
int n,d;
printf("enter a numbern");
scanf("%d",&n);
d=fac(n);
printf(“factorial = %d",d);
}
int fac(int n)
{
int f;
for(f=1;n>=1;n--)
f=f*n;
return(f);
}

8. Types of Functions
They are two types of function:
1. Pre define function (Library function)
2. User define function

9. Pre define function (Library function)
A function that has already be define in the library of ‘C’
language or library developed by other programmer is
called Pre define function (Library function).
Ex:-
scanf, printf, puts, gets, etc.

10. User define function
A function define by the programmer itself that are called
User define function and it can be n number of function.

11. How the Function works?
 “C” program doesn't execute the statement in function until the
function is called.
 When function is called the program can send the function
information in the form of one or more argument.
 When the function is used it is referred to as the called
function.
 Functions often use data that is passed to them from the calling
function.

12. Cont..
 Data is passed from the calling function to a called function by
specifying the variables in a argument list.
 Argument list cannot be used to send data. Its only copy
data/value/variable that pass from the calling function.
 The called function then performs its operation using the copies
and either it may be return some value or not.

13. Function Prototypes
 Provides the compiler with the description of functions that
will be used later in the program
 Its define the function before it been used/called
 Function prototypes need to be written at the beginning of the
program.
 The function prototype must have : a return type indicating the
variable that the function will be return
 Syntax for Function Prototype
return_type function_name(parameter _list);

14. Advantages of Function
 It is much easier to write a structured program
where a large program can be divided into a
functions.
 Allowing the code to be called many times
 Easier to read and update
 It is easier to debug a structured program and easy
to find and fix error.

15. Conclusion
Function is a name block of statement which is used to performs
a specific task. A function is either call by value or by reference.
They are two types of function pre define or user define. A
function name is must be unique and it can be n no. of function
which can be called n no. times means there is no limit. For using
a function it is easy to write it, test it, and debug it.

16. Thank You