This PowerPoint presentation provides a clear and beginner-friendly explanation of functions in the C programming language. It covers both built-in functions and user-defined functions, including examples with and without return values. Topics also include recursion, prime number check, factorial program, and the use of global and static variables. Ideal for BCA students, beginners in C, or anyone preparing for programming exams.

1. FUNCTIONS

2. Function
• A function is a block of reusable
code designed to perform a
specific task
• There’s 2 types of functions in c.
• 1) Built-in function
• 2) User define function
User define has 2 parts in it.
i) With return
ii) Without return

3. Function
• Benefits:
• Code reusability
• Improved Readability and
Maintainability,
• Reduced Redundancy

4. Function
• Built-in functions:
• built-in functions (also known as
library functions) are pre-defined
functions provided by the C
Standard Library.
• These functions perform specific,
commonly-needed operations,
such as handling input and output,
manipulating strings
#include <stdio.h>
#include <string.h>
int main() {
char str[] = "Hello, World!";
printf("Length: %lun", strlen(str));
printf("First character: %cn", str[0]);
return 0;
}

5. Function
• User define functions:
• User-defined function is a function
created by the programmer to
perform a specific task.
• Unlike built-in functions, user-
defined functions are custom
functions
// Function declaration
int add(int a, int b);
int main()
{
int result = add(5, 3); // Function call
printf("Result: %d", result);
return 0;
}
// Function definition
int add(int a, int b)
{
return a + b;
}

6. Function
• User define functions:
• With return:
• functions perform a task and return
a result to the caller.
• type specifies the type of value the
function will return
• In this example “add()” return an
int value which is sum of a and b
int add(int a, int b)
{
return a + b;
}
int main()
{
int result = add(3, 4);
printf("Sum: %d", result);
return 0;
}

7. Function
• User define functions:
• With out return:
• perform a task but do not return
any value
• Return type for such functions is
void, indicating that no value
returned.
void greet() {
printf("Hello, World!n");
}
int main() {
greet(); // Calls greet() to print the
message
return 0;
}

8. Function
A) Write a C Program that
defines a function to add
first n numbers.
#include <stdio.h>
int addFirstN(int n)
{
int sum = 0;
for (int i = 1; i <= n; i++)
{
sum += i;
}
return sum;
}
int main()
{
int n;
printf("Enter a number: ");
scanf("%d", &n);
printf("Sum of first %d numbers: %dn", n,
addFirstN(n));
return 0;
}

9. Function
B) Write a function in the
program to return 1 if
number is prime
otherwise return 0.
#include <stdio.h>
int isPrime(int num) {
if (num <= 1) return 0;
for (int i = 2; i * i <= num; i++) {
if (num % i == 0) return 0;
}
return 1;
}
int main() {
int num;
printf("Enter a number: ");
scanf("%d", &num);
if (isPrime(num))
printf("%d is a prime number.n", num);
else
printf("%d is not a prime number.n", num);
return 0;
}

10. Function
C) Program to Find
Factorial of a Number
Using Recursion.
#include <stdio.h>
int factorial(int n) {
if (n <= 1) return 1; // Base case
return n * factorial(n - 1); // Recursive call
}
int main() {
int num;
printf("Enter a number: ");
scanf("%d", &num);
printf("Factorial of %d is: %dn", num,
factorial(num));
return 0;
}

11. Function
D) Program Using Global
Variable and Static
Variable.
#include <stdio.h>
int globalCounter = 0; // Global variable
void increment() {
static int staticCounter = 0; // Static variable
globalCounter++;
staticCounter++;
printf("Global Counter: %d, Static Counter:
%dn", globalCounter, staticCounter);
}
int main() {
for (int i = 0; i < 3; i++) {
increment();
}
return 0;
}

12. Thank you