What is function?

what-is-function

A piece of code within a larger program, which is written to perform a specific task is called function. It is independent of the remaining code of the program. Functions are the building blocks of C program.

A program may have many functions. Each functions has a unique name. The function is called for executing with the reference of its name. A function can be called for executing by the main () function or any other function of the program.

Functions provide structured programming approach. In structured programming, a large program is divided into smaller units. These small units are called functions or modules, or subprograms.

Importance of Function

If a program is written without using functions then there may be repetition of the same piece of code at various places. So thje size of the program may become very large it becomes very difficult to modify and debug the program.

Using functions, a program can be divided into different units. Each unit can be managed easily. A piece of code for each unit is written as a function. The same piece of code is written only once in the program as a function. This function can be called again and again from multiple places in a program to perform a particular task. The size of program is reduced. The program can easily be modified and debugged.

Benefits / Advantages of using function

There are many advantages or benefits of using functions in C. the main advantages are as follows:

Easy to write a program

A problem becomes easier if it is broken down into smaller tasks. Similarly, writing a large program becomes easier if it is divided into smaller parts. Each part is called a function.

Easy to understand and modify the program

When large program is divided into subprograms, the complexity of their program is reduced. It makes easier to understand the logic of the program. It is also easy to make changes and detect errors in the program.

Eliminate duplicate code

The same piece of code is written only once in the program as a function. The function is called for executing with the reference to its name only. Thus same piece of code does not have to written at multiple places in the program to perform the same task. This reduces the size of the program.

Reusability

The function written for one program can be re-used into another new program. Thus, the programmer can develop a program quickly in a very short time. Suppose a function is written to draw a line graph. This function can be used in any program that needs to draw a line graph.

Type of Function

There are two type of function

·         Built-in functions

·         User-defined functions

Built-in Functions

The predefined functions that are part of the programming language are called built-in functions. The built-in functions are also called library functions. These functions can be used for different purpose. These functions make the programmer’s job easier to design the program. The program development time is also reduced by using built-in functions.

Every language has a large number of built-in functions. These functions are declared in the header files for example the printf() functions are declared in header file stdioi.h Similarly clrscr functions declared in conio.h header file. Every language has a large number of header files. Each header file has information of related function

User-Defined Functions

The functions written by user or programmer are called user-defined functions. These functions are also called programmer-defined functions. A user-defined function is written to perform a specific task. A program may contain many user-defined functions.

A user-defined functions has the following main parts:

Function declaration or prototype

Function definition