### User Defined Functions in C

Almost all the programming languages uses functions. Functions are
the entities which are grouping a set of statements which do a specific
job or set of jobs.

Example: sum of integers, sum of float number, complex number addition.

All the above three can be implemented as a single function or three separate functions.

When someone wants to use that, a function can be simply called.

So function implementation happens as

This is the actual function definition which shows the function implementation.

for the above syntax here is the function

The last is the function call, which when being needed a simple call will make the function to work. Here is the example

name of the function is :

return type is

parameters are:

T S Pradeep Kumar

Example: sum of integers, sum of float number, complex number addition.

All the above three can be implemented as a single function or three separate functions.

When someone wants to use that, a function can be simply called.

So function implementation happens as

- Function prototype or Function declaration
- Function definition or function implementation
- Function call

**Function prototype**- It is necessary to specify the name of the function, the parameters and the return type to the compiler that the function is being defined in this program.
- The prototype ends with a semicolon

int sum(int, int); //function prototype

**Function Definition**This is the actual function definition which shows the function implementation.

for the above syntax here is the function

int sum(int a, int b)The above function is returning an integer, hence int is specified. If a function is not returning any thing, a void can be used.

{

int c;

c=a+b;

return c;

}

**Function call**The last is the function call, which when being needed a simple call will make the function to work. Here is the example

int main()Once the function is called, the control goes to the actual implementation and execute the statements inside the function and the value is returned to the main function.

{

int x,y,z;

scanf(“%d %d”,&x,&y);

z=sum(x,y);//function call

printf(“The sum is %d”, z);

return 0;

}

**Components of a function**- Name of the function
- Return type
- Parameters or arguments

name of the function is :

**sum()**return type is

**: int**parameters are:

**int, int**T S Pradeep Kumar