Computer-programming-User-defined-function-1.pptx

What is a Function?
A function is a named, independent section of C# code that performs a
specific task and optionally returns a value to the calling program.
SYNTAX:
<access_modifier> <return_type> <function_name> (parameters)
{
body
}

Access modifiers
- keywords used to specify accessibility of a member or a type. An access modifier
allows us a way to handle which member or type has an access or not has an access
to certain features in a program.
Function return type
- specifies the data type that the function returns to the calling program. The return
type can be of C#’s data types: char, int, long, float, or double. You can also define a
function that doesn’t return a value, a return type of void. Here are some examples:
int func1(. . .) /* return a type int */
float func2(. . .) /* return a type float */
void func3(. . .) /* returns nothing */

Function name
You can name a function anything you like, as long as you follow
the rules for C# variable names. A function name must be unique
(not assigned to any other function or variable). It’s a good idea
to assign a name that reflects what the function does.
An entry in a function header; it serves as a “place holder” for an
argument. A function’s parameters are fixed; they do not change during
program execution.
Parameter

an actual value passed to the function by the calling program. Each time a function is
called, it can be passed different arguments.
Argument

Where to Put Functions?
/* start of source code */
. . .
function1( )
{
. . .
}
function2( )
{
. . .
}
static void Main(string [] args)
{
. . .
}
/* end of source code */

Example 1: Void and Parameterless Function
static public void PrintMyName() //function definition
{
Console.WriteLine(“Jose Protacio Rizal Mercado y Alonzo Realonda”);
}
{
PrintMyName(); //function call
Console.ReadKey(true);
}

Example 2:Functions with Return Value and Parameters
static int Sum(int x, int y)
{
return x + y;
}
{
int number1 = 5;
int number2 = 10;
int total;
total = Sum(number1, number2);
Console.WriteLine(“Sum is: “ + total);
}

Example 3: A program that will calculate the cube of a number
static long cube(long x)
{
long x_cube;
x_cube = x*x*x;
return x_cube;
}
{
long input, answer;
Console.Write(“Enter an integer value: “);
input = Convert.ToInt64(Console.ReadLine());
answer = cube(input);
Console.WriteLine(“The cube of “ + input + “is “ + answer);
}

Example 4: Finding Maximum Value
using System;
namespace CalculatorApplication
{
class NumberManipulator
{
public int FindMax(int num1, int num2)
{
/* local variable declaration */
int result;
if (num1 > num2)
result = num1;
else
result = num2;
return result;
}
static void Main(string[] args)
{
/* local variable definition */
int a = 100;
int b = 200;
int ret;
NumberManipulator n = new NumberManipulator();
//calling the FindMax method
ret = n.FindMax(a, b);
Console.WriteLine("Max value is : {0}", ret );
Console.ReadLine();
}
}
}

Example 5: A method can call itself. This is known as recursion.
Recursion is made for solving problems that can be broken
down into smaller, repetitive problems. It is especially good for
working on things that have many possible branches and are
too complex for an iterative approach. Following is an example
that calculates factorial for a given number using a recursive
function:

using System;
namespace CalculatorApplication
{
class NumberManipulator
{
public int factorial(int num)
{
/* local variable declaration */
int result;
if (num == 1)
{
return 1;
}
else
{
result = factorial(num - 1) * num;
return result;
}
}
static void Main(string[] args)
{
NumberManipulator n = new NumberManipulator();
//calling the factorial method
Console.WriteLine("Factorial of 6 is : {0}", n.factorial(6));
Console.ReadLine();
}
}
}

Computer-programming-User-defined-function-1.pptx

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