Functions Overview in C Language part-1

Functions Overview

Function is a basic building block of a C program. Any C program can be assumed as a collection of several functions. Function is a block of code which has some name for identification.

Key Point of Function

Function is a block of code, which has some name for identification

Any C program can have any number of functions. At least one function should be there in the program

Function names must be unique. No two functions can share same names

No keyword is a functions, so do not misinterpreted by the syntax of if, while, switch, return(), sizeof(), etc, they are not functions

Function cannot be defined inside body of another function

Function call, function definition and function declaration are three different terminologies with different meanings, so never used them interchangeably

You can call a function from a function any number of times, but can define only once.

Function is a way to achieve modularization.

Splitting up of a bigger task into several smaller sub tasks is known as modularization

Functions are of two types, Predefined and user defined

printf, scanf are examples of predefined function

main is an example of user defined function

Functions can be defined in any sequence in the program, without affecting the flow of the program

Function execution depends on the call of a function. Function can never execute in the life of program if it is not called from anywhere in the program

Function declaration is also known as function prototype

Function declaration for the predefined functions resides in the header files

Function definitions for all predefined functions resides in the library file

Programmer has to provide declaration of the user defined function

Execution of program begins with main function

Operating system calls main

Any function can call main

Any function can call itself, known as recursion

Benefits of functions

Easy to read

Easy to modify

Easy to debug

Avoids rewriting of code

Better memory utilization

Following example can be used to understand the flow of the program, when it contains several functions.

int main()
{
printf(“\nI am in function main() “);
a();
printf(“\nI am in function main() “);
b();
printf(“\nI am in function main() “);
a();
printf(“\nI am in function main() “);
return(0);
}
a()
{
printf(“\nI am in function a() “);
}
b()
{
printf(“\nI am in function b() “);
a( );
}

Output:

I am in function main()

I am in function a()

I am in function main()

I am in function b()

I am in function a()

I am in function main()

I am in function a()

I am in function main()