C Functions

Functions are basic blocks of codes , till now we have been using a lot of functions , can you remember , yes one of it is the prints function , before going to discuss function let us see the syntax for a function

Function name ( function parameter )

{

Function body

}

So function name is quite easy to understand , so the function parameter is what we pass into that function , we can say that it is the doorway for a function

Function body is the part where all the action happens

This figure might help to understand this well

 

But programmatically how this work , to see this lets make a simple program that display a message from a function outside main and how it works

function()

{

printf(“hello world”);

}

main()

{

printf(“inside main”);

function();

getch();

}

As we can see we are calling the function “function” inside the main by just referring its name ,  this is how we call a function , we can call as many functions as we want , we can call multiple functions but for that the functions should exist first

One thing to remember is that if a variable is declared inside a function then that variable is just accessible to that function only , in order to make a variable accessible to all the functions we make a global variable , it is nothing but a variable declared at the very above of every function , this example will make this clear

#include<stdio.h>

int total; //global variable

int i;

input() //function

{

printf("Enter a number\n");

scanf("%d",&i); // taking a value and changing the value of i for all function

}

output()

{

total = i *2; // global variable total calculation

}

main() // main fnction

{

input(); // calling input function

 output(); // calling output function

printf("total is %d",total); //displaying the total from main

getch();

}

As we can see , "total" and "I" are global variable and input and output are two user defined functions

We can also pass parameter to a different function and then process the result , this example will make this more clear

int total;

take(int a)

{

total = a * 2;

printf("\n\ndouble is %d",total);

}

main()

{

     

int i;

printf("Enter a number\n");

scanf("%d",&i);

take(i);

getch();

}  

Here we take the variable i in main and pass it to function called take , in take inside its parenthesis we declare a variable of same data type that accepts the value of i , once a=I then everything becomes easy now

It is also possible that a function can return a value to the mother function like

int add(int n1 ,int n2)

{

int result;

result = n1 + n2;

return result;

}

main()

{

Int z;

z = add( 3,5);

printf(“%d”,z);

getch();

}

In this program we first pass value to the add function , the int before the function name signify that this function will return a int value , then the add function accepts the value and returns the result which get stored in the variable called z , and we display the “z” , this is how returning of a value works in a function