User Defined Function in C language

“Work hard in silence , and let the success be the noise”

Hello everyone!!!
I’m back with new article on user defined function.
Soo let’s start quickly 🙂

The functions that we create in a program are known as user defined functions or in other words you can say that a function created by user is known as user defined function.

Syntax of Function:-
return_type function_name (argument list)
Set of statements – Block of code

Points to be noted while writing function:-
1) return_type: Return type can be of any data type such as int, double, char, void, short etc.
2) function_name: It can be anything, however it is advised to have a meaningful name for the functions so that it would be easy to understand the purpose of function just by seeing it’s name.
3) argument list: Argument list contains variables names along with their data types. These arguments are kind of inputs for the function. For example – A function which is used to add two integer variables, will be having two integer argument.
4) Block of code: Set of C statements, which will be executed whenever a call will be made to the function.

•Function Declarations/Function Prototype:-
A function declaration tells the compiler about a function name and how to call the function. The actual body of the function can be defined separately. A function declaration has the following parts-
return_type function_name( parameter list );

•Suppose we need to write the prototype for function for adding two numbers then the prototype will be as follows:-
int sum (int num1, int num2);

Calling a Function:-
1)While creating a C function, you give a definition of what the function has to do. To use a function, you will have to call that function to perform the defined task.
2) When a program calls a function, the program control is transferred to the called function. A called function performs a defined task and when its return statement is executed or when its function-ending closing brace is reached, it returns the program control back to the main program.
3) To call a function, you simply need to pass the required parameters along with the function name, and if the function returns a value, then you can store the returned value.

Now let us see some examples, which will make my concept more clear.

Q1) write a C program to add two numbers using functions.

int addition(int, int);
int addition(int num1, int num2)
int sum;
sum = num1+num2;
return sum;
main( )
int a,b,c;
printf(“Enter number 1: “);
printf(“Enter number 2: “);
c = addition(a, b);
printf (“Output: %d”, c);

Enter number 1: 24
Enter number 2: 67
Output: 91

Q2) C Program using function to calculate maximum of two numbers.

int max(int num1, int num2);
int main ( )
int a = 100;
int b = 200;
int res;
res = max(a, b);
printf( “Max value is : %d\n”, res );
int max(int num1, int num2)
int result;
if (num1 > num2)
result = num1;
result = num2;
return result;

Max value is : 200

This is the simple programs to make you’ll understand easily.
Will see some more related programs in the upcoming article. Soo keep reading 🙂

Hope you all must have got an idea about user defined function.
Soo see you all in the next article.. Till then good bye.
Have a wonderful day ahead 🙂

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