20250624 10:30 Chapter 5 : Functions and Pointers Made Simple

     

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- Functions in C 

What’s a Function?

A function is a block of code that does one specific job.

It’s like a mechanic — you just call him, and he knows what to do.
In C, we call a function using its name + ().

or 

Think of a Restaurant!

Imagine a restaurant kitchen.

You (the customer) place an order for masala dosa.

You don’t go into the kitchen, chop vegetables, cook or anything.
You just say:

"One masala dosa, please!"

Behind the scenes, the chef does all the work and brings you your dosa.

main() {
    message();  // calling the function
}

message() {
    printf("Smile!");
}

Key Points:

• Every C program starts with main().

• You can have many functions, but only one main().

• Functions call each other; control jumps to the called function and returns after it finishes.

• Functions can even call themselves (called recursion).

Passing Values

You can send data to functions using arguments.

sum = add(10, 20);  // 10 and 20 are passed to add()

int add(int a, int b) {
    return a + b;   // sends result back
}

Actual arguments = from main()
Formal arguments = received by the called function

The return Magic




return sends back a result.

return (a + b); // sends the sum back

You can return:

• a number → return (5);

• nothing → return; (not recommended)

• no value at all → use void function

Notes:

• Functions can’t be defined inside each other.

• Changing a value in the function won’t change it in main() — only a copy is passed.

• Use functions to keep code clean and avoid repeating yourself.

Why Use Functions?

• Reuse code

• Make programs easier to read and fix

• Break big problems into small tasks