What is function in C with example?
A  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser is a block of statements that performs a specific  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser. Let's say you are writing a C program and you need to perform a same task in that program more than once. In such case you have two options: a) Use the same set of  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser every time you want to perform the task
b) Create a  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser to perform that task, and just  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser it every time you need to  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser that task.

Why we need functions in C?
Functions are used because of following reasons –
a) To improve the  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser of code.
b) Improves the reusability of the code, same  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser can be used in any program rather than writing the same code from  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser.
c)  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser of the code would be easier if you use functions, as  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser are easy to be traced.
d) Reduces the  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser of the code, duplicate set of statements are replaced by function  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser.

How many types of functions are there in C?
There are  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser types of function in C programming:  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser library functions.  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser- argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser functions.

What is Predefined standard library function?
Standard library functions are also known as  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser-in functions.  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser such as puts(), gets(),  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser(), scanf() etc are  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser library functions. These functions are already  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser in header files (files with .h  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser are called  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser files such as stdio.h), so we just call them whenever there is a need to use them.
For example,  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser() function is defined in < argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser.h> header file so in order to use the printf() function, we need to include the header file in our program using #include .

What is User-defined function?
The  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser that we create in a  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser are known as user  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser functions or in other words you can say that a function  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser by user is known as user defined function.Syntax of a function
return_type  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser_name ( argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser list)
{
Set of  argumentbuiltcallcallscreatedDebuggingdefinederrorsextensionsfunctionFunctionsheaderperformprintfprogramreadabilityscratchsizeStandardstatementsstdiotasktwoUser – Block of code
}