Functions in c

A function is a self-contained block of code that performs a specific task. Think of it as a "sub-program" that you can write once and use (call) whenever you need it.

Using functions makes your code modular, easier to read, and reusable.

1. The Three Parts of a Function

To use a function, you generally need these three pieces:

1. Function Declaration (Prototype): Tells the compiler about the function's name, return type, and parameters (usually at the top of the file).

2. Function Definition: The actual body of the code where the work happens.

3. Function Call: When you tell the program to go execute that block.

4. Simple Code Example

   #include <stdio.h>
   
   // 1. Declaration (Prototype)
   int addNumbers(int a, int b);
   
   int main() {
       int x = 5, y = 10, sum;
   
       // 3. Function Call
       sum = addNumbers(x, y); 
   
       printf("The sum is: %d\n", sum);
       return 0;
   }
   
   // 2. Definition
   int addNumbers(int a, int b) {
       int result = a + b;
       return result; // Sending the value back to main
   }

Expected Output:

The sum is: 15

3. Key Concepts

Return Types

Functions can return a value or nothing at all:

• int, float, char: Returns a value of that type.

• void: Use this keyword if the function doesn't return anything (e.g., just printing a message).

Parameters (Arguments)

These are the inputs you pass to the function.

• Formal Parameters: The variables defined in the function header (int a, int b).

• Actual Parameters: The real values passed during the call (x, y)

5. Recursion

• A function is "recursive" if it calls itself. This is a powerful way to solve mathematical problems like factorials or Fibonacci sequences.

int factorial(int n) {
    if (n <= 1) return 1; // Base case (to stop the loop)
    return n * factorial(n - 1); // Recursive call
}