The document contains information about Tarandeep Kaur, including her name, section, and roll number. It then lists and describes various topics related to functions in C++, including definition of functions, function calling, function prototypes, void functions, local vs global variables, function overloading, and recursion. Examples are provided to illustrate function calling, passing arguments, return values, and differences between call by value and call by reference.

1. Name – Tarandeep Kaur
Section – N2
Roll No. – 115331

2.  Definition of functions
 Function calling
 Function definition
 Void function
 Remarks on function
 Local v/s Global variables
 Function call methods
 Concept of recursion
 Function overloading

3.  A function is a subprogram that acts on data
and often returns a value.

4.  Functions invoked by a function–call-statement which
consist of it’s name and information it needs (arguments)
 Boss To Worker Analogy
 A Boss (the calling/caller function) asks a worker (the
called function) to perform a task and return result when
it is done.
Boss
Main
Worker
Worker Worker
Function Z
Function A Function B
Worker Worker
Note: usual main( ) Calls other
Function B1 Function B2 functions, but other functions
can call each other

5. • Functions called by writing
functionName (argument);
or
functionName(argument1, argument2, …);
• Example
cout << sqrt( 900.0 );
• sqrt (square root) function
• The preceding statement would print 30
• All functions in math library return a double
 Function Arguments can be:
- Constant sqrt(9);
- Variable sqrt(x);
- Expression sqrt( x*9 + y) ;
sqrt( sqrt(x) ) ;

6. • Calling/invoking a function
– sqrt(x);
– Parentheses an operator used to call function
• Pass argument x
• Function gets its own copy of arguments
– After finished, passes back result
Function Name argument Output
3
cout<< sqrt(9);
Parentheses used to enclose argument(s)

7.  Functions
◦ Modularize a program
◦ Software reusability
 Call function multiple times
 Local variables
◦ Known only in the function in which they are defined
◦ All variables declared in function definitions are local variables
 Parameters
◦ Local variables passed to function when called
◦ Provide outside information

8.  Function prototype
◦ Tells compiler argument type and return type of function
◦ int square( int );
 Function takes an int and returns an int
◦ Explained in more detail later
 Calling/invoking a function
◦ square(x);
◦ Parentheses an operator used to call function
 Pass argument x
 Function gets its own copy of arguments
◦ After finished, passes back result

9.  Example function
int square( int y )
{
return y * y;
}
 return keyword
◦ Returns data, and control goes to function’s
caller
 If no data to return, use return;
◦ Function ends when reaches right brace
 Control goes to caller
 Functions cannot be defined inside other
functions

10. // Creating and using a programmer-defined function.
#include <iostream.h>
Function prototype: specifies
int square( int ); // function prototype data types of arguments and
return values. square
int main()
expects an int, and returns
{
// loop 10 times and calculate and output
an int.
// square of x each time
for ( int x = 1; x <= 10; x++ )
cout << square( x ) << " "; // function call
cout << endl;
Parentheses () cause function to be called.
When done, it returns the result.
return 0; // indicates successful termination
} // end main
// square function definition returns square of an integer
int square( int y ) // y is a copy of argument to function
{
return y * y; // returns square of y as an int
Definition of square. y is a
copy of the argument passed.
} // end function square Returns y * y, or y squared.
1 4 9 16 25 36 49 64 81 100

11. // Finding the maximum of three floating-point (real) numbers.
#include <iostream.h>
double maximum( double, double, double ); // function prototype
int main()
{
double number1, number2;
double number3; Function maximum takes 3
arguments (all double) and
cout << "Enter three real numbers: "; returns a double.
cin >> number1 >> number2 >> number3;
// number1, number2 and number3 are arguments to the maximum function call
cout << "Maximum is: "
<< maximum( number1, number2, number3 ) << endl;
return 0; // indicates successful termination
} // end main
// function maximum definition. x, y and z are parameters
double maximum( double x, double y, double z )
{
double max = x; // assume x is largest Enter three real numbers: 99.32 37.3 27.1928
if ( y > max ) // if y is larger, Maximum is: 99.32
max = y; // assign y to max
Enter three real numbers: 1.1 3.333 2.22
if ( z > max ) // if z is larger,
Maximum is: 3.333
max = z; // assign z to max
return max; // max is largest value
} // end function maximum

12.  Function prototype contains
◦ Function name
◦ Parameters (number and data type)
◦ Return type (void if returns nothing)
◦ Only needed if function definition after function call
 Prototype must match function definition
◦ Function prototype
double maximum( double, double, double );
◦ Definition
double maximum( double x, double y, double z
)
{
…
}

13. If the Function does not RETURN result, it is called void
Function
#include<iostream.h>
void add2Nums(int,int);
main()
{ int a, b;
cout<<“enter tow Number:”;
cin >>a >> b;
add2Nums(a, b)
return 0;
}
void add2Nums(int x, int y)
{
cout<< x<< “+” << y << “=“ << x+y;
}

14. If the function Does Not Take Arguments specify this with EMPTY-LIST OR
write void inside
#include<iostream.h>
void funA();
void funB(void)
main()
{ Will be the same
funA(); in all cases
funB();
return 0;
}
void funA()
{
cout << “Function-A takes no arqumentsn”;
}
void funB()
{
cout << “Also Function-B takes No argumentsn”;
}

15.  Local variables
◦ Known only in the function in which they are defined
◦ All variables declared inside a function are local variables
 Parameters
◦ Local variables passed to function when called (passing-
parameters)
 Variables defined outside and before function main:
◦ Called global variables
◦ Can be accessible and used anywhere in the entire
program

16. #include<iostream.h>
int x,y; //Global Variables
int add2(int, int); //prototype
main()
{ int s;
x = 11;
y = 22;
cout << “global x=” << x << endl;
cout << “Global y=” << y << endl;
s = add2(x, y);
cout << x << “+” << y << “=“ << s;
cout<<endl;
cout<<“n---end of output---n”;
return 0;
} global x=11
int add2(int x1,int y1) global y=22
{ int x; //local variables Local x=44
x=44;
11+22=33
cout << “nLocal x=” << x << endl;
return x1+y1; ---end of output---
}

17.  Call by value
• A copy of the value is passed
 Call by reference
• The caller passes the address of the value
 Call by value
 Up to this point all the calls we have seen are call-by-value, a copy
of the value (known) is passed from the caller-function to the called-
function
 Any change to the copy does not affect the original value in the
caller function
 Advantages, prevents side effect, resulting in reliable software

18.  Call By Reference
 We introduce reference-parameter, to perform call by reference. The caller
gives the called function the ability to directly access the caller’s value, and to
modify it.
 A reference parameter is an alias for it’s corresponding argument, it is stated in
c++ by “flow the parameter’s type” in the function prototype by an
ampersand(&) also in the function definition-header.
 Advantage: performance issue
void function_name (type &);// prototype
main()
{
-----
------
}
void function_name(type &parameter_name)

19. #include<iostream.h>
int squareVal(int); //prototype call by value function
void squareRef(int &); // prototype call by –reference function
int main()
{ int x=2; z=4;
cout<< “x=“ << x << “before calling squareVal”;
cout << “n” << squareVal(x) << “n”; // call by value
cout<< “x=“ << x << “After returning”
cout<< “z=“ << z << “before calling squareRef”;
squareRef(z); // call by reference
cout<< “z=“ << z<< “After returning squareRef”
return 0;
}
x=2 before calling squareVal
int squareVal(int a)
4
{
x=2 after returning
return a*=a; // caller’s argument not modified
z=4 before calling squareRef
}
z=16 after returning squareRef
void squarRef(int &cRef)
{
cRef *= cRef; // caller’s argument modified
}

20.  Main calls another function…..normal
 A function calls another function2….normal
 A function calls itself ?! Possible?? YES
A recursive function is one that call itself.

21.  A recursive function is called to solve a problem
 The function knows to solve only the simplest cases
or so-called base-cases
 Thus if the function called with a base-case, it simply
returns a result. But if it is called with more complex
problem, the function divides the problem into two
conceptual pieces, one knows how to do, and another
doesn't know what to do.
 The second case/piece must resemble the original
problem, but be a slightly simpler/smaller version of
the original problem

22.  Function overloading
◦ Functions with same name and different parameters
◦ Should perform similar tasks
 I.e., function to square ints and function to square floats
int square( int x) {return x * x;}
float square(float x) { return x * x; }
 A call-time c++ complier selects the proper function by
examining the number, type and order of the parameters

23.  THANKS