Study notes on Functions

1. Functions in C
A brief study

2. Functions
• Function is a self-contained block or a sub-
program of one or more statements that
performs a special task when called.

3. Example of functions
• Hotel management
– Front Office
– Reservation
– Housekeeping
– Telephone

4. Hotel management

5. Hotel
Customer()
{
House_keeping(); //Function call
}
House_keeping() //Function definition
{
Cleans rooms;
}

6. Hotel
Customer() //calling function
{
House_keeping(); //Function call
}
House_keeping() //called function
{
Cleans rooms;
}

7. Add two numbers
main()
{
int a,b;
int c;
printf(“Enter the value of a”);
scanf(“%d”,&a);
printf(“Enter the value of b”);
scanf(“%d”,&b);
c=a+b;
printf(“Answer is:%d”,c);
}

8. Add two numbers using functions
main()
{ add(x,y)
int a,b; {
int c; z=x+y;
printf(“Enter the value of a”); printf(“%d”,z);
scanf(“%d”,&a); }
printf(“Enter the value of b”);
scanf(“%d”,&b);
add(a,b);
}

9. Arguments/Parameters
• Arguments are used mostly in functions.
• it can be any input parameter which a
function can use to do it's work.
• Example: sin(x) sin is a function
x is it's argument.

10. Arguments/Parameters
• Actual arguments:
• Arguments of calling function
• Formal arguments:
• Arguments of called function

11. Add two numbers using functions
main() formal arguments
{ add(x,y)
int a,b; {
int c; z=x+y;
printf(“Enter the value of a”); printf(“%d”,z);
scanf(“%d”,&a); }
printf(“Enter the value of b”);
scanf(“%d”,&b);
add(a,b); //function call
} actual arguments

12. Argument/Parameter list
a=2
b=4
add(a,b);
add(x,y)
x=2
y=4

13. return statement
• function uses return statement to return the
value to the called function.
• Exit from the called function.
return(expression);

14. Hotel
Customer() //calling function
{
House_keeping(); //Function call
}
House_keeping() //called function
{
Cleans rooms;
return 0;
}

15. Hotel
Customer() //calling function
{
Front_office(Money); //Function call
}
Front_office(Money) //called function
{
return receipt;
}

16. Types of functions
1. No arguments and no return type
2. No arguments and return type
3. With arguments and no return type
4. With arguments and return type

17. Passing arguments
• The arguments passed to function can be of two
types.
1. Values passed – Call by value
2. Address passed – Call by reference

18. Call by value
• main()
{
int x=50, y=70;
add(x,y);
}
add(int x1,int y1)
{
int z1;
z1=x1+y1;
printf(“%d”,z1);
}

19. Call by reference
• main()
{
int x=50, y=70;
add(&x,&y);
}
add(int *x1,int *y1)
{
int z1;
z1=x1+y1;
printf(“%d”,z1);
}

20. Call by reference
• Address is passed using symbol ‘&’
value is accessed using symbol ‘*’
x=50 &x=2000 *x=50
y=70 &y=2008 *y=70

21. Thank you