C Functions
In this tutorial, you will learn about the C Library functions and return statement with the help of examples.
Function
- A Function is a block of code which is used to performs a specific task.
- Functions are used to provide modularity & code reusability to a program.
- The Function is also known as procedure or subroutine in other programming languages.
- Every C program has at least one function, which is main().
- Dividing a complex problem into smaller chunks makes our program easy to understand and reusable.
Why do we need Functions?
- It divides the program into separate well-defined functions so that each function can be written and tested separately.
- Understanding, coding and testing becomes very easy as they are separated.
- Writing functions avoids rewriting the same code over and over.
- As the functions are divided the workload can also be divided among the programmers.
Advantages of Functions
- It makes the program clear and easy to understand.
- Single Functions can be tested easily for errors.
- It saves time from typing th same function again and again.
- It helps to modify the program easily without changing the structure of a program.
- Function can be called multiple times as per requirement.
Types of Function
There are two types of functions in C programming:
- Standard Library Functions : are the functions which are Predefined in C Language.
- User-defined Function : are the functions which are Created by users.
Standard library functions
- Library functions are the built-in functions in C programming.
- Library functions are those type of functions which are already defined, compiled and stored in different header files of standard C library.
- Users can use library functions by calling the functions directly; they don’t need to write the functions themselves.
For example :
Some common library functions in C programming are printf(), scanf(), etc.
In order to use mathematical functions such as sqrt() and abs(), we need to
include the header file <math.h>.
Example : Standard Library function
#include <stdio.h>
// declaring "cmath" header file to use mathematical functions
#include <math.h>
int main() {
int number;
double squareRoot;
number = 9;
// sqrt() is a library function to calculate the square root
squareRoot = sqrt(number);
printf("Square root of %d is %lf ",number,squareRoot);
return 0;
}
Output
Square root of 9 = 3.000000
In this program, the sqrt() library function is used to calculate the square root of a number.
The function declaration of sqrt() is defined in the math.h header file. That’s why we need to use the code #include <math.h> to use the sqrt() function.
Visit standard library functions in C programming to learn more.
Return Statement
The Return statement is used to terminate the execution of a function and transfer program control back to the calling function.
It can also specify a value to be returned by the function.
Syntax :
void Number() {
// statement
}
- This means the function is not returning any value.
- It’s also possible to return a value from a function.
- For this, we need to specify the
returnType
of the function during function declaration. - Then, the
return
statement can be used to return a value from a function.
For example,
int add (int a, int b) {
return (a + b);
}
Here, we have the data type int
instead of void
. This means that the function returns an int
value.
The code return (a + b);
returns the sum of the two parameters as the function value.
The return
statement denotes that the function has ended. Any code after return
inside the function is not executed.