Functions in C
As programs grow larger, writing everything inside main()
becomes confusing and hard to manage.
To solve this problem, C provides functions. Functions help us divide a program into smaller, manageable parts.
What Is a Function?
A function is a block of code that performs a specific task.
Once written, a function can be called multiple times from different parts of the program.
This improves:
- Code readability
- Reusability
- Maintainability
Why Functions Are Important
Think of functions like real-life tasks:
- Cooking rice
- Sending an email
- Calculating salary
Each task is done separately and reused when needed. Functions work the same way in programming.
Types of Functions in C
There are two main types of functions:
- Library Functions – provided by C
- User-Defined Functions – created by programmer
Examples of library functions:
printf()scanf()strlen()
Structure of a User-Defined Function
A function has three main parts:
- Function declaration
- Function definition
- Function call
Function Declaration
The declaration tells the compiler about:
- Function name
- Return type
- Parameters
int add(int, int);
Function Definition
The definition contains the actual code of the function.
int add(int a, int b) {
return a + b;
}
Function Call
A function is executed when it is called.
sum = add(10, 20);
Complete Example: Function to Add Two Numbers
#include <stdio.h>
int add(int a, int b) {
return a + b;
}
int main() {
int result;
result = add(5, 7);
printf("Sum = %d", result);
return 0;
}
Here:
- The function
add()performs addition main()calls the function- The returned value is printed
Functions With and Without Return Value
Functions can be:
- With return value – returns data
- Without return value – uses
void
void greet() {
printf("Welcome to C Programming");
}
Real-World Thinking
Functions help teams work efficiently.
- One person writes a function
- Others reuse it
- Errors are fixed in one place
This is why functions are the backbone of large software systems.
Mini Practice
- Create a function to find square of a number
- Create a function to check even or odd
- Create a function to find maximum of two numbers
Quick Quiz
Q1. What is a function?
Q2. Why are functions used?
Q3. What keyword is used for no return value?
Q4. Where does program execution start?
Q5. Can a function be called multiple times?