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Vijesh Nair
Vijesh Nair
Assistant Professor
Dept. of Computer Engineering
Vijesh Nair
Introduction
What is function?
How functions will work?
How to declare a function in C language?
What are the different types of functions are
there in C language?
Example programs.
Vijesh Nair
Introduction
Vijesh Nair
Modular Programming
Break a large problem into smaller pieces
Smaller pieces sometimes called ‘modules’ or
‘subroutines’ or ‘procedures’ or functions
Divide and Conquer
Vijesh Nair
Why Modular Programming?
Helps in managing the complexity of the
program
- Smaller blocks of code - Easier to read
Encourages re-use of code
Within a particular program or across different programs
Allows independent development of code
Provides a layer of ‘abstraction’
Vijesh Nair
What is function?
Function is a set of instructions to carry out a particular task.
The Function after processing returns a single value.
In other word, we say a Function is a group of statements
that can perform any particular task.
Function in programming is a segment that groups a number
of program statements to perform specific task
Vijesh Nair
Every C program has at least one function, which is main().
We have already used functions like…..
Vijesh Nair
Every function in C must have two things…
A function declaration tells the compiler about a function's
name, return type, and parameters.
A function definition provides the actual body of the
function.
Vijesh Nair
A function declaration tells the compiler about a function's
name, return type, and parameters.
A function declaration must be done within main function or
before main function.
Vijesh Nair
A function definition must be done before main function or
after main function.
A function definition provides the actual body of the
function.
Vijesh Nair
Types of functions?
Predefined
Userdefined
Vijesh Nair
Predefined functions
Actually all predefined functions in C Language are defined
inside in any one of the header files.
If the functionality of a function is defined by the compiler
those functions are called predefined functions.
The functionality of the predefined function is fixed, users
cannot change or redefine it.
Vijesh Nair
Predefined functions
Predefined functions are also called as System Defined
functions or Library functions.
NOTE
Vijesh Nair
User-defined functions
User-defined functions are small programs that you can
write to perform an operation.
If the functionality of a function is defined by the user those
functions are called user-defined functions.
Users are free to define their own code for the user-defined
functions. Every user-defined function must have the
following….
Vijesh Nair
Declaring User-defined functions
Syntax
Example
We also call it as Function Prototype
NOTE
Vijesh Nair
Definition of User-defined functions
Syntax
Example
Vijesh Nair
Calling User-defined functions
Syntax
Example
Vijesh Nair
Working of Functions
Vijesh Nair
Example Program
void main()
{
int a, b, c;
void addition(int , int);
printf(“We are in main…..n”);
printf(“Enter any two numbers: ”);
scanf(“%d%d”, &a, &b);
addition(a, b);
printf(“We are again in main…..”);
}
void addition(int x, int y)
{
printf(“SUM = %dn”, x+y);
}
Vijesh Nair
Important terms in functions
It is nothing but a function declaration
It is used to initiate the function execution. That means this
line decides when a function has to be perform its task.
It is nothing but the function definition. It decides what is to
be done by the function on a function call.
Vijesh Nair
Example Program
void main()
{
int a, b, c;
void addition(int , int);
printf(“We are in main…..n”);
printf(“Enter any two numbers: ”);
scanf(“%d%d”, &a, &b);
addition(a, b);
printf(“We are again in main…..”);
}
void addition(int x, int y)
{
printf(“SUM = %dn”, x+y);
}
Prototype
Calling
Called
Vijesh Nair
Parameters & Return Value
Parameters are the data values which are passed from
calling function to called function
Return value is the data value which passed from called
function to calling function
For a function we can have any number of parameters
For a function we can have only one return value
In a function the total number of parameters and the order
of the parameters must be same in all function prototype,
function calling and function definition
Vijesh Nair
Parameters & Return Value
To return a value from called function to calling function we
use ‘return’ statement
Vijesh Nair
Parameter types
In C programming language there are two types of
parameters
Vijesh Nair
These are the parameters used at the time of function
calling
Whenever we pass actual parameters copy of its value is
sent to the called function but not entire variable
Vijesh Nair
These are the parameters used at called function as
receivers of the actual parameters
The order of the actual parameters and their datatypes
should exactly match with the order and datatypes of the
formal parameters
Vijesh Nair
Function types
Based on the parameters and return value, functions are
classified into FOUR types
Vijesh Nair
Without Parameters and without Return value
In this type, there is no data transfer between calling and
called functions
Simple control transfer from calling function to called
function, executes called function body and comes back to
the calling function.
Everything is performed within the called function like
reading data, processing data and displaying result.
This type of functions are used to print some message,
line….
Vijesh Nair
Example Program:
void main()
{
void add();
printf(“We are in main….n”);
add();
printf(“We are again in main….n”);
}
void add()
{
int a,b,c;
printf(Enter any two numbers: );
scanf(“%d%d”, &a, &b);
c = a + b;
printf(“Result = %d”, c);
}
Vijesh Nair
void main( )
{
void add( );
printf(“We are in main….n”);
add( );
printf(“We are again in main….n”);
}
void add( )
{
int a,b,c;
printf(Enter any two numbers: );
scanf(“%d%d”, &a, &b);
c = a + b;
printf(“Result = %d”, c);
}
Control
No input
Control
No return value
Vijesh Nair
With Parameters and without Return value
In this type, there is data transfer from calling to called
function, but not from called to calling function.
Simple control transfer from calling function to called
function along with some data (parameters), executes called
function body and comes back to the calling function
without any data.
This type of functions are depend on the calling function.
Generated result is utilized by called function and nothing
will be sent back to the calling function.
Vijesh Nair
Example Program:
void main()
{
void add( int, int );
printf(“We are in main….n”);
add( 10, 20);
printf(“We are again in main….n”);
}
void add(int a, int b)
{
int c;
c = a + b;
printf(“Result = %d”, c);
}
Vijesh Nair
void main( )
{
void add( int, int );
printf(“We are in main….n”);
add( 10, 20 );
printf(“We are again in main….n”);
}
void add( int a, int b)
{
int c;
c = a + b;
printf(“Result = %d”, c);
}
Control
10 & 20 as input
Control
No return value
Vijesh Nair
Without Parameters and with Return value
In this type, there is no data transfer from calling to called
function, but from called to calling function one data is sent.
Simple control transfer from calling function to called
function, executes called function body and a data value is
sent back to the calling function from called function.
This type of functions are called function is independent. It
reads data, process data and result is sent back to the calling
function.
Vijesh Nair
Example Program:
void main()
{
int c;
int add( );
printf(“We are in main….n”);
c = add( );
printf(“Result = %dn”, c);
}
int add( )
{
int a, b;
printf(“Enter any two numbers:”);
scanf(“%d%d”, &a, &b);
return (a + b);
}
Vijesh Nair
void main( )
{
int c;
int add( );
printf(“We are in main….n”);
c = add( );
printf(“Result = %dn”, c);
}
void add( )
{
int a,b;
printf(Enter any two numbers: );
scanf(“%d%d”, &a, &b);
return (a + b);
}
Control
No input
Control
30 as return value
input values for a & b are 10 & 20 respectively
Vijesh Nair
With Parameters and with Return value
In this type, there is data transfer from calling to called
function, and from called to calling function one data is sent
back.
Control transfer from calling function to called function
along with data, executes called function body and a data
value is sent back to the calling function from called
function.
In this type of functions are called & calling functions both
dependent on each other.
Vijesh Nair
Example Program:
void main()
{
int c;
int add( int, int );
printf(“We are in main….n”);
c = add( 10, 20 );
printf(“Result = %dn”, c);
}
int add( int a, int b)
{
return (a + b);
}
Vijesh Nair
void main( )
{
int c;
int add( int, int );
printf(“We are in main….n”);
c = add( 10, 20 );
printf(“Result = %dn”, c);
}
void add( int a, int b)
{
return (a + b);
}
Control
10 & 20 as input
Control
30 as return value
Vijesh Nair
Different ways to make a function call
There are THREE ways of making function call…
Vijesh Nair
1. From main function
We have already seen making a function call from main
function.
When we make a function call from main, the control
transfers to called function, executes it, again comes back to
the main function.
Vijesh Nair
2. From another user-defined function
We can also make a function call from another user-defined
function.
Vijesh Nair
void main()
{
function1();
}
void function1()
{
function2();
}
void function2()
{
body of the function;
}
Vijesh Nair
3. From same function
We can also make a function call from same function. That
means function calls itself
If a function calls itself, then it is called as “RECURSION”.
When a function calls itself until the last call is invoked till
that time the first call also remains open.
At every time, a function invoked, the function returns the
result of previous call.
Vijesh Nair
void main( )
{
printf(“This is example of Recursion!!!”);
main( );
}
Example Program:
Output:
This is example of Recursion!!!
This is example of Recursion!!!
This is example of Recursion!!!
This is example of Recursion!!!
…….
Vijesh Nair
int factorial( int );
void main( )
{
int fact, n;
printf(“Enter any positive integer: ”);
scanf(“%d”, &n);
fact = factorial( n );
printf(“Factorial of %d is %d”, n, fact);
}
int factorial( int n )
{
int temp;
if( n == o)
return 1;
else
temp = n * factorial( n-1 );
return temp;
}
Example Program:
Vijesh Nair
int factorial( int );
void main( )
{
int fact, n;
printf(“Enter any positive integer: ”);
scanf(“%d”, &n);
fact = factorial( n );
printf(“Factorial of %d is %d”, n,
fact);
}
int factorial( int n )
{
int temp;
if( n == o)
return 1;
else
temp = n * factorial( n-1 );
return temp;
}
Vijesh Nair
int factorial( int n )
{
int temp;
if( n == o)
return 1;
else
temp = n * factorial( n-1 );
return temp;
}
n = 3 n
3
temp
int factorial( int n )
{
int temp;
if( n == o)
return 1;
else
temp = n * factorial( n-1 );
return temp;
}
3 * factorial(2)
n = 2
n
2
temp
int factorial( int n )
{
int temp;
if( n == o)
return 1;
else
temp = n * factorial( n-1 );
return temp;
}
2 * factorial(1)
n = 1
int factorial( int n )
{
int temp;
if( n == o)
return 1;
else
temp = n * factorial( n-1 );
return temp;
1 * factorial(0)
n
1
0
n
temp
temp
n = 0
1
1
1
1*1 = 1
2
2*1 = 2
2
3*2 = 6
6
6
Memory Allocation
Vijesh Nair

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6.3 c-Functions.ppt

  • 1. Vijesh Nair Vijesh Nair Assistant Professor Dept. of Computer Engineering
  • 2. Vijesh Nair Introduction What is function? How functions will work? How to declare a function in C language? What are the different types of functions are there in C language? Example programs.
  • 4. Vijesh Nair Modular Programming Break a large problem into smaller pieces Smaller pieces sometimes called ‘modules’ or ‘subroutines’ or ‘procedures’ or functions Divide and Conquer
  • 5. Vijesh Nair Why Modular Programming? Helps in managing the complexity of the program - Smaller blocks of code - Easier to read Encourages re-use of code Within a particular program or across different programs Allows independent development of code Provides a layer of ‘abstraction’
  • 6. Vijesh Nair What is function? Function is a set of instructions to carry out a particular task. The Function after processing returns a single value. In other word, we say a Function is a group of statements that can perform any particular task. Function in programming is a segment that groups a number of program statements to perform specific task
  • 7. Vijesh Nair Every C program has at least one function, which is main(). We have already used functions like…..
  • 8. Vijesh Nair Every function in C must have two things… A function declaration tells the compiler about a function's name, return type, and parameters. A function definition provides the actual body of the function.
  • 9. Vijesh Nair A function declaration tells the compiler about a function's name, return type, and parameters. A function declaration must be done within main function or before main function.
  • 10. Vijesh Nair A function definition must be done before main function or after main function. A function definition provides the actual body of the function.
  • 11. Vijesh Nair Types of functions? Predefined Userdefined
  • 12. Vijesh Nair Predefined functions Actually all predefined functions in C Language are defined inside in any one of the header files. If the functionality of a function is defined by the compiler those functions are called predefined functions. The functionality of the predefined function is fixed, users cannot change or redefine it.
  • 13. Vijesh Nair Predefined functions Predefined functions are also called as System Defined functions or Library functions. NOTE
  • 14. Vijesh Nair User-defined functions User-defined functions are small programs that you can write to perform an operation. If the functionality of a function is defined by the user those functions are called user-defined functions. Users are free to define their own code for the user-defined functions. Every user-defined function must have the following….
  • 15. Vijesh Nair Declaring User-defined functions Syntax Example We also call it as Function Prototype NOTE
  • 16. Vijesh Nair Definition of User-defined functions Syntax Example
  • 17. Vijesh Nair Calling User-defined functions Syntax Example
  • 19. Vijesh Nair Example Program void main() { int a, b, c; void addition(int , int); printf(“We are in main…..n”); printf(“Enter any two numbers: ”); scanf(“%d%d”, &a, &b); addition(a, b); printf(“We are again in main…..”); } void addition(int x, int y) { printf(“SUM = %dn”, x+y); }
  • 20. Vijesh Nair Important terms in functions It is nothing but a function declaration It is used to initiate the function execution. That means this line decides when a function has to be perform its task. It is nothing but the function definition. It decides what is to be done by the function on a function call.
  • 21. Vijesh Nair Example Program void main() { int a, b, c; void addition(int , int); printf(“We are in main…..n”); printf(“Enter any two numbers: ”); scanf(“%d%d”, &a, &b); addition(a, b); printf(“We are again in main…..”); } void addition(int x, int y) { printf(“SUM = %dn”, x+y); } Prototype Calling Called
  • 22. Vijesh Nair Parameters & Return Value Parameters are the data values which are passed from calling function to called function Return value is the data value which passed from called function to calling function For a function we can have any number of parameters For a function we can have only one return value In a function the total number of parameters and the order of the parameters must be same in all function prototype, function calling and function definition
  • 23. Vijesh Nair Parameters & Return Value To return a value from called function to calling function we use ‘return’ statement
  • 24. Vijesh Nair Parameter types In C programming language there are two types of parameters
  • 25. Vijesh Nair These are the parameters used at the time of function calling Whenever we pass actual parameters copy of its value is sent to the called function but not entire variable
  • 26. Vijesh Nair These are the parameters used at called function as receivers of the actual parameters The order of the actual parameters and their datatypes should exactly match with the order and datatypes of the formal parameters
  • 27. Vijesh Nair Function types Based on the parameters and return value, functions are classified into FOUR types
  • 28. Vijesh Nair Without Parameters and without Return value In this type, there is no data transfer between calling and called functions Simple control transfer from calling function to called function, executes called function body and comes back to the calling function. Everything is performed within the called function like reading data, processing data and displaying result. This type of functions are used to print some message, line….
  • 29. Vijesh Nair Example Program: void main() { void add(); printf(“We are in main….n”); add(); printf(“We are again in main….n”); } void add() { int a,b,c; printf(Enter any two numbers: ); scanf(“%d%d”, &a, &b); c = a + b; printf(“Result = %d”, c); }
  • 30. Vijesh Nair void main( ) { void add( ); printf(“We are in main….n”); add( ); printf(“We are again in main….n”); } void add( ) { int a,b,c; printf(Enter any two numbers: ); scanf(“%d%d”, &a, &b); c = a + b; printf(“Result = %d”, c); } Control No input Control No return value
  • 31. Vijesh Nair With Parameters and without Return value In this type, there is data transfer from calling to called function, but not from called to calling function. Simple control transfer from calling function to called function along with some data (parameters), executes called function body and comes back to the calling function without any data. This type of functions are depend on the calling function. Generated result is utilized by called function and nothing will be sent back to the calling function.
  • 32. Vijesh Nair Example Program: void main() { void add( int, int ); printf(“We are in main….n”); add( 10, 20); printf(“We are again in main….n”); } void add(int a, int b) { int c; c = a + b; printf(“Result = %d”, c); }
  • 33. Vijesh Nair void main( ) { void add( int, int ); printf(“We are in main….n”); add( 10, 20 ); printf(“We are again in main….n”); } void add( int a, int b) { int c; c = a + b; printf(“Result = %d”, c); } Control 10 & 20 as input Control No return value
  • 34. Vijesh Nair Without Parameters and with Return value In this type, there is no data transfer from calling to called function, but from called to calling function one data is sent. Simple control transfer from calling function to called function, executes called function body and a data value is sent back to the calling function from called function. This type of functions are called function is independent. It reads data, process data and result is sent back to the calling function.
  • 35. Vijesh Nair Example Program: void main() { int c; int add( ); printf(“We are in main….n”); c = add( ); printf(“Result = %dn”, c); } int add( ) { int a, b; printf(“Enter any two numbers:”); scanf(“%d%d”, &a, &b); return (a + b); }
  • 36. Vijesh Nair void main( ) { int c; int add( ); printf(“We are in main….n”); c = add( ); printf(“Result = %dn”, c); } void add( ) { int a,b; printf(Enter any two numbers: ); scanf(“%d%d”, &a, &b); return (a + b); } Control No input Control 30 as return value input values for a & b are 10 & 20 respectively
  • 37. Vijesh Nair With Parameters and with Return value In this type, there is data transfer from calling to called function, and from called to calling function one data is sent back. Control transfer from calling function to called function along with data, executes called function body and a data value is sent back to the calling function from called function. In this type of functions are called & calling functions both dependent on each other.
  • 38. Vijesh Nair Example Program: void main() { int c; int add( int, int ); printf(“We are in main….n”); c = add( 10, 20 ); printf(“Result = %dn”, c); } int add( int a, int b) { return (a + b); }
  • 39. Vijesh Nair void main( ) { int c; int add( int, int ); printf(“We are in main….n”); c = add( 10, 20 ); printf(“Result = %dn”, c); } void add( int a, int b) { return (a + b); } Control 10 & 20 as input Control 30 as return value
  • 40. Vijesh Nair Different ways to make a function call There are THREE ways of making function call…
  • 41. Vijesh Nair 1. From main function We have already seen making a function call from main function. When we make a function call from main, the control transfers to called function, executes it, again comes back to the main function.
  • 42. Vijesh Nair 2. From another user-defined function We can also make a function call from another user-defined function.
  • 43. Vijesh Nair void main() { function1(); } void function1() { function2(); } void function2() { body of the function; }
  • 44. Vijesh Nair 3. From same function We can also make a function call from same function. That means function calls itself If a function calls itself, then it is called as “RECURSION”. When a function calls itself until the last call is invoked till that time the first call also remains open. At every time, a function invoked, the function returns the result of previous call.
  • 45. Vijesh Nair void main( ) { printf(“This is example of Recursion!!!”); main( ); } Example Program: Output: This is example of Recursion!!! This is example of Recursion!!! This is example of Recursion!!! This is example of Recursion!!! …….
  • 46. Vijesh Nair int factorial( int ); void main( ) { int fact, n; printf(“Enter any positive integer: ”); scanf(“%d”, &n); fact = factorial( n ); printf(“Factorial of %d is %d”, n, fact); } int factorial( int n ) { int temp; if( n == o) return 1; else temp = n * factorial( n-1 ); return temp; } Example Program:
  • 47. Vijesh Nair int factorial( int ); void main( ) { int fact, n; printf(“Enter any positive integer: ”); scanf(“%d”, &n); fact = factorial( n ); printf(“Factorial of %d is %d”, n, fact); } int factorial( int n ) { int temp; if( n == o) return 1; else temp = n * factorial( n-1 ); return temp; }
  • 48. Vijesh Nair int factorial( int n ) { int temp; if( n == o) return 1; else temp = n * factorial( n-1 ); return temp; } n = 3 n 3 temp int factorial( int n ) { int temp; if( n == o) return 1; else temp = n * factorial( n-1 ); return temp; } 3 * factorial(2) n = 2 n 2 temp int factorial( int n ) { int temp; if( n == o) return 1; else temp = n * factorial( n-1 ); return temp; } 2 * factorial(1) n = 1 int factorial( int n ) { int temp; if( n == o) return 1; else temp = n * factorial( n-1 ); return temp; 1 * factorial(0) n 1 0 n temp temp n = 0 1 1 1 1*1 = 1 2 2*1 = 2 2 3*2 = 6 6 6 Memory Allocation