undefined | unit 4 user defined functions

C PPS

UNIT 4USER DEFINED FUNCTIONS Q1) Explain user-defined functions?A1)User define function is the block of code written by programmer to perform a particular task. As compiler doesn’t have any idea about the user define function so programmer has to define and declare these functions inside the program body. Programmer can define these function outside the main function but declaration of user define function should present in main function only. Whenever compiler executes function call (function declaration) then compiler shift the flow of program execution to the definition part of user define function. Q2) Explain recursion?A2)In programming languages, if a program allows you to call a function inside the same function, then it is called a recursive call of the function.

void recursion() {

recursion(); /* function calls itself */

}

int main() {

recursion();

}

The C programming language supports recursion, i.e., a function to call itself. But while using recursion, programmers has to be careful to define an exit condition from the function, otherwise it will go into an infinite loop.Recursive functions are useful to solve many mathematical problems, such as calculating the factorial of a number, generating Fibonacci series, etc. Q3) Write a program to find the factorial of a number using recursion?A3)

#include<stdio.h>
#include<conio.h>

int rec (int x);

void main()
{
int a, fact;
printf("\nEnter any number: ");
scanf ("%d", &a);
fact=rec(a);
printf("\nFactorial Value = %d", fact);
getch();

}

int rec (int x)
{
int f;
if (x==1)
return (1);
else
f=x*rec(x-1);
return (f);

}

Q4) What are functions in C?A4)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.The C standard library provides numerous built-in functions that your program can call. For example, strcat() to concatenate two strings, memcpy() to copy one memory location to another location, and many more functions.A function can also be referred as a method or a sub-routine or a procedure, etc.Defining a FunctionThe general form of a function definition in C programming language is as follows −

return_type function_name( parameter list ) {

body of the function

}

Q5) Explain the difference between function and recursion?A5) ‘declare’, ‘define’ and call a function. You can identify a function as a component of whole program, with a separate body, starting and ending indications, a curly bracket ‘{}’ in case of ‘C’, input parameters and output type being part of it.

Eg:

<return type> fooBar(<data type> input_var|,...)

{//Body start indicator of a function

*Some code, which solves the problem

*for which the function is designed!

return <some value of type as return type of the function>

}//Body end indicator of a function Recursion on the other hand is a concept, it is not a separate component, it is implemented within function itself. It is more of a technique which makes solving complicated problems easier for a computer programmer.We call a function is recurring or implementing recursion, when somewhere within the body of function, it fires a call to itself, that is where all the context of execution of that function is saved in a stack and function makes a fresh call to itself. Once terminating condition(Condition which ends recursion) is encountered, unwinding phase is activated, and previous states are recreated in Last in First Out fashion, by popping top of the stack, and continues until stack is empty.Recursion is easy to code but it is highly computation intensive, and not all problems can be solved by recursion, there are a few famous ones though, like Fibonacci series, Tower of Hanoi, Factorial problem, etc:

Eg:

int Fact(int n) //Recursive function to calculate factorial of n

{

if(n==0 || n==1) //Terminating condition

return 1;

return n * fact(n-1); //Recursion statement(condition calling itself)

}

Q6) Write a program to add two numbers using functions?A6)#include <stdio.h>int add(int a, int b); //function declarationint main(){ int a=10,b=20; int c=add(10,20); //function call printf("Addition:%d\n",c); getch();}int add(int a,int b) //function body{ int c; c=a+b; return c;}Output:Addition:30Q7) Write a program to find the maximum of two numbers using C ?A7)

#include <stdio.h>

// An example function that takes two parameters 'x' and 'y'

// as input and returns max of two input numbers

int max(int x, int y)

{

if (x > y)

return x;

else

return y;

}

// main function that doesn't receive any parameter and // returns integer. int main(void) { int a = 10, b = 20;
	// Calling above function to find max of 'a' and 'b' int m = max(a, b); printf("m is %d", m); return 0;
	}

Q8) Write a program to find the given number is even or odd.A8)

#include <stdio.h>

/**

* Function to check even or odd

* Returns 1 is num is even otherwise 0

int isEven(int num)

{

return !(num & 1);

}

int main()

{

int num;

/* Input number from user */

printf("Enter any number: ");

scanf("%d", &num);

/* If isEven() function returns 0 then the number is even */

if(isEven(num))

{

printf("The number is even.");

}

else

{

printf("The number is odd.");

}

return 0;

}

Q9) Write a program to find reverse a string? A9)

#include <stdio.h>

#include <string.h>

int main()

{

char s[100];

printf("Enter a string to reverse\n");

gets(s);

strrev(s);

printf("Reverse of the string: %s\n", s);

return 0;

}

C reverse string program output:Reverse string C program output

Q10) Write a program to find LCM of a number.A10)

		#include <stdio.h> int main() { int i, num1, num2, max, lcm=1;
	/* Input two numbers from user / printf("Enter any two numbers to find LCM: "); scanf("%d%d", &num1, &num2); / Find maximum between num1 and num2 / max = (num1 > num2) ? num1 : num2; / First multiple to be checked / i = max; / Run loop indefinitely till LCM is found / while(1) { if(i%num1==0 && i%num2==0) printf("Enter any two numbers to find LCM: "); scanf("%d%d", &num1, &num2); / Find maximum between num1 and num2 / max = (num1 > num2) ? num1 : num2; / First multiple to be checked / i = max; / Run loop indefinitely till LCM is found */ while(1)
{ if(i%num1==0 && i%num2==0) { /* * If 'i' divides both 'num1' and 'num2' * then 'i' is the LCM. / lcm = i; / Terminate the loop after LCM is found / break; } / * If LCM is not found then generate next * multiple of max between both numbers */ i += max; } printf("LCM of %d and %d = %d", num1, num2, lcm); return 0; }

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