functions in c language_functions in c language.pptx

Functions in C language
Mehak Bhatia
(Assistant Professor)
IIMT College of Science and Technology
Greater Noida

Functions
• A function is a group of statements that together
perform a task.
• Functions are sets of statements that take inputs,
perform some operations, and produce results
 Functions are used to perform certain actions, and
they are important for reusing code:
 Define the code once, and use it many times.
Mehak Bhatia, IIMT College of Science
and Technology

Functions
 Within a function, there are a number of
programming statements enclosed by {}, having
certain meanings and performing certain
operations.
 The operation of a function occurs only when it
is called.
 Rather than writing the same code for different
inputs repeatedly, we can call the function
instead of writing the same code over and over
again.
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Creating a Function
Syntax:
void function_name()
{
// code to be executed
}
Example:
void myFunction()
{
printf("Hello World!");
}
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Explanation of Example
 myFunction() is the name of the function.
 Inside the function (the body), we have to add
the code that defines what the function should
do.
 void means that the function does not have a
return value.
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Why use Functions?
 The function can reduce the repetition of the
same statements in the program.
 The function makes code readable.
 There is no fixed number of calling functions it
can be called as many times as you want.
 The function reduces the size of the program.
 Once the function is declared you can just use it
without thinking about the internal working of
the function.
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Syntax of Functions
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Defining a Function
The general form of a function definition in
programming language is as follows :
return_type function_name( parameter list )
{
body of the function
}
A function definition in C programming consists of
a function header and a function body.
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Here are all the parts of a function −
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 Return Type − A function may return a value.
The return_type is the data type of the value
the function returns. Some functions perform
the desired operations without returning a value.
In this case, the return_type is the
keyword void.
 Function Name − This is the actual name of
the function. The function name and the
parameter list together constitute the function
signature.

 Parameters − A parameter is like a placeholder.
When a function is invoked, you pass a value to the
parameter.
 This value is referred to as actual parameter or
argument.
 The parameter list refers to the type, order, and
number of the parameters of a function.
 NOTE: Parameters are optional; that is, a function
may contain no parameters.
 Function Body − The function body contains a
collection of statements that define what the
function does.
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Given below is the source code for a function called max().This
function takes two parameters num1 and num2 and returns the
maximum value between the two −
int max(int num1, int num2)
{
int result;
if (num1 > num2)
result = num1;
else
result = num2;
return result;
} Mehak Bhatia, IIMT College of Science
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Function Declarations
 A function declaration tells the compiler about a
function name and how to call the function. The
actual body of the function can be defined
separately.
 A function declaration has the following parts −
return_type function_name( parameter list );
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For the above defined function max(), the function
declaration is as follows −
int max(int num1, int num2);
NOTE: Parameter names are not important in function
declaration only their type is required, so the following is
also a valid declaration −
int max(int, int);
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 Function declaration is required when you define
a function in one source file and you call that
function in another file.
 In such case, you should declare the function at
the top of the file calling the function
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Calling a Function
• While creating a C function, you give a definition of
what the function has to do. To use a function, you will
have to call that function to perform the defined task.
• When a program calls a function, the program control is
transferred to the called function.
• A called function performs a defined task and when its
return statement is executed or when its function-ending
closing brace is reached, it returns the program control
back to the main program.
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To call a function, you simply need to pass the required parameters along
with the function name, and if the function returns a value, then you can
store the returned value. For example −
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Example of function calling
#include <stdio.h>
int sum(int a, int b) // Function takes 2 parameters as inputs
{
return a + b; // Returns the sum
}
int main()
{
// Calling sum function and storing its value in add variable
int add = sum(10, 30);
printf("Sum is: %d", add);
return 0;
}
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Output
Sum is: 40
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How C function works?
•Declaring a function: Declaring a function is a
step where we declare a function. Here we define
the return types and parameters of the function.
•Calling the function: Calling the function is a
step where we call the function by passing the
arguments in the function.
.

 Executing the function: Executing the function
is a step where we can run all the statements
inside the function to get the final result.
 Returning a value: Returning a value is the
step where the calculated value after the
execution of the function is returned.
 Exiting the function: Exiting the function is the
final step where all the allocated memory to the
variables, functions, etc is destroyed before
giving full control to the main function.
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Types of Functions
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User Defined Function
Functions that the programmer creates are
known as User-Defined functions
or “tailor-made functions”. User-
defined functions can be improved and
modified according to the need of the
programmer. Whenever we write a
function that is case-specific and is not
defined in any header file, we need to
declare and define our own functions
according to the syntax.Mehak Bhatia, IIMT College of Science
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Advantages of User-Defined functions
 Changeable functions can be modified
as per need.
 The Code of these functions is reusable
in other programs.
 These functions are easy to understand,
debug and maintain.
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#include <stdio.h>
int sum(int a, int b)
{
return a + b;
}
// Driver code
int main()
{
int a = 30, b = 40;
// function call
int res = sum(a, b);
printf("Sum is: %d", res);
return 0;
}
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OutputSum is: 70
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Java Method Overloading
If we have to perform only one operation, having
same name of the methods increases the
readability of the program.
There are two ways to overload the method in
java:
 By changing number of arguments
 By changing the data type
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By changing number of arguments
class Adder{
static int add(int a,int b)
{return a+b;
}
static int add(int a,int b,int c)
{
return a+b+c;
} }
class TestOverloading1{
public static void main(String[] args){
System.out.println(Adder.add(11,11));
System.out.println(Adder.add(11,11,11));
}}
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Output
22
33
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Library Function
A library function is also referred to as a “built-in
function”. A compiler package already exists that
contains these functions, each of which has a
specific meaning and is included in the package.
Built-in functions have the advantage of being
directly usable without being defined, whereas
user-defined functions must be declared and
defined before being used.
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 For Example:
 pow(), sqrt(), strcmp(), strcpy() etc.
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 Advantages of C library functions
 C Library functions are easy to use and
optimized for better performance.
 C library functions save a lot of time i.e,
function development time.
 C library functions are convenient as they
always work.
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Advantage of methods:
 #include <math.h>
 #include <stdio.h>

 // Driver code
 int main()
 {
 double Number;
 Number = 49;

 // Computing the square root with
 // the help of predefined C
 // library function
 double squareRoot = sqrt(Number);

 printf("The Square root of %.2lf = %.2lf",
 Number, squareRoot);
 return 0;
 }
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 OutputThe Square root of 49.00 =
7.00
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THANK YOU
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