Function in c
A function is a self contained code or group of statements or block of statement that perform specific well defined task in program or coherent task when it is called.
User can declarer function as per requirement, it’s totally depending on user how to define function. Multiple functions also defined to perform specific task in a program.
By using function a large program can be divided into sub programs.
Generally every C program contain at least one function which is main().
There two types of function :
1. Library function
2. User defined function
1. Library function
Library functions are the system defined function it can’t be modified, it can only read and can be used in program.
These function are always provided with every C compiler
Source code of library function are pre complied and only object code used by the programmer by linking to the code using linker
e.g printf(),scanf(),getch(),clrscr().
2. User defined function
When the user defines function according requirement is called user defined function.
Function definition
Function definition consists of complete description and code of the function for specific well defined task.
It tells about task of function , what are its inputs required and what are its expected out put .
Function definition consist two parts function header and function body
Syntax:-
return type function name(type1 arg1,type2 arg2,...)
{
Local variable declaration;
Statement 1;
Statement 2;
Return value
}
If the function does not going return any value to the calling point then the syntax looks like
function name(type 1 arg1, type2 arg2, ...)
{
Local variable declaration;
Statement 1;
Statement 2;
Return value
}
The return type declare the type of the value that function will return if not declared it is assumed to be int by default.
if a function returns no value that time keyword void can be used before the fun ction name.
The body of the function consist the group of statements or block which consists of local variable declaration statement and optional return statement.
If the variables are declared inside a function is only local variables to that function only. You can’t be used anywhere in the program .
Example of Function Creating a user defined function
Creating a user defined function multiplication()
#include<stdio.h>
int multiplication(int num1, int num2) //function prototype
int main()
{
int var1, var2, res;
printf("Enter number 1: ");
scanf("%d",&var1);
printf("Enter number 2: ");
scanf("%d",&var2);
res = multiplication(var1, var2); //function call
printf ("Output: %d", res);
return 0;
}
int multiplication(int num1, int num2)//function definition
{
int mul;
mul = num1*num2;
return mul; //return statement
}
Function Call
When the function is called the control of the program is transferred to function definition by calling it and once function executed with return value, the control again transfer to the main function of a program.
Syntax of function call:
Function Name (arg1,arg2,arg3,…);
In above example multiplication(var1, var2); statement inside the main() function.
Function Prototype
It is the declaration of a function which specifies name of function, parameters and return type. it doesn’t contain function body.
It tells to compiler that the functions will have number of arguments and return type of a function required , it also tell about data type of a function parameter.
It also gives the information of function may be later used in program and If function not defined before it used, it must be declared by specifying the return type and the types of the parameters.
Syntax of Function Prototype
return type function name(type 1 argument1, type2 argument2, ….)
in above example multiplication(int num1, int num2) is the function prototype.
Passing argument to the function
When we pass variables to the functions we refer as argument and if we used argument inside the function call are called actual argument,
If we use argument in the function definition are known as formal arguments.
So when we pass to the function and formal parameter need to match otherwise compiler will give error.
In above example var1 and var2 are passed during the function call and parameter num1 and num2 accept the passed argument in the function definition
Hi I am Avinash S. working as teacher and blogger, my aim to start this blog is to make the most challenging topics easy for everyone to learn. I’m always open for feedback and you can send me your review about this blog.