Functions In C Programming Ppt

Posted By admin On 27/11/21

A function depending an whether the arguments are present or not and whether a value is returned or not, may belong to one of following categories

  1. Function with no return values, no arguments
  2. Functions with arguments, no return values
  3. Functions with arguments and return values
  4. Functions with no arguments and return values.

1.).In this category, the function has no arguments. It does not receive any data from the calling function. Similarly, it doesn’t return any value. The calling function doesn’t receive any data from the called function. So, there is no communication between calling and called functions.
2.)In this category, function has some arguments . it receives data from the calling function, but it doesn’t return a value to the calling function. The calling function doesn’t receive any data from the called function. So, it is one way data communication between called and calling functions.
Eg: Printing n Natural numbers

It is necessary to have one main function section in every C program. This section contains two parts, declaration and executable part. The declaration part declares all the variables that are used in executable part. These two parts must be written in between the opening and closing braces. This program is divided in two functions: addition and main.Remember that no matter the order in which they are defined, a C program always starts by calling main.In fact, main is the only function called automatically, and the code in any other function is only executed if its function is called from main (directly or indirectly). In the example above, main begins by declaring the variable. TUTORIALS POINT Simply Easy Learning Page 2 Today, C is the most widely used and popular System Programming Language. Most of the state -of the art softwares have been implemented using C. Today's most popular Linux OS and RBDMS MySQL have been written in C. C was initially used for system development work, in particular the programs that make up. Generic programming is an approach of C programming where generic types are used as parameters so that they can work for various cases of suitable data type and data structure. The template is the basis for establishing the concept of generic programming, which entails writing code in a way that is independent of a particular type.

Enter n value: 5
1 2 3 4 5
In the main() function, n value is passed to the nat() function. The n value is now stored in the formal argument n, declared in the function definition and subsequently, the natural numbers upto n are obtained.
3.)In this category, functions has some arguments and it receives data from the calling function. Simillarly, it returns a value to the calling function. The calling function receives data from the called function. So, it is two-way data communication between calling and called functions.

Enter n: 5
Factorial of the number : 120
4.)In this category, the functions has no arguments and it doesn’t receive any data from the calling function, but it returns a value to the calling function. The calling function receives data from the called function. So, it is one way data communication between calling and called functions.

Many a times, we need to repeat the same process in a program multiple times. It is difficult for us to define functions for every function call of the same process.Based on the calling of the functions by the user in a program, functions are classified as

  1. Recursive functions
  2. Non-Recursive functions
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A function is a group of statements that together perform a task. Every C program has at least one function, which is main(), and all the most trivial programs can define additional functions.

You can divide up your code into separate functions. How you divide up your code among different functions is up to you, but logically the division is such that each function performs a specific task.

Functions In C++ Programming Language


A function declaration tells the compiler about a function's name, return type, and parameters. A function definition provides the actual body of the function.

The C standard library provides numerous built-in functions that your program can call. For example, strcat() to concatenate two strings, memcpy() to copy one memory location to another location, and many more functions.

A function can also be referred as a method or a sub-routine or a procedure, etc.

Defining a Function

The general form of a function definition in C programming language is as follows −

A function definition in C programming consists of a function header and a function body. Here are all the parts of a function −

  • Return Type − A function may return a value. The return_type is the data type of the value the function returns. Some functions perform the desired operations without returning a value. In this case, the return_type is the keyword void.

  • Function Name − This is the actual name of the function. The function name and the parameter list together constitute the function signature.

  • Parameters − A parameter is like a placeholder. When a function is invoked, you pass a value to the parameter. This value is referred to as actual parameter or argument. The parameter list refers to the type, order, and number of the parameters of a function. Parameters are optional; that is, a function may contain no parameters.

  • Function Body − The function body contains a collection of statements that define what the function does.


Given below is the source code for a function called max(). This function takes two parameters num1 and num2 and returns the maximum value between the two −

Function Declarations

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 −

For the above defined function max(), the function declaration is as follows −

Parameter names are not important in function declaration only their type is required, so the following is also a valid declaration −

Function declaration is required when you define a function in one source file and you call that function in another file. In such case, you should declare the function at the top of the file calling the function.

Calling a Function

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.

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.

Functions In C Programming Ppt

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. For example −

We have kept max() along with main() and compiled the source code. While running the final executable, it would produce the following result −

Function Arguments

If a function is to use arguments, it must declare variables that accept the values of the arguments. These variables are called the formal parameters of the function.

Formal parameters behave like other local variables inside the function and are created upon entry into the function and destroyed upon exit.

Functions In C Programming Ppt Example

While calling a function, there are two ways in which arguments can be passed to a function −

Sr.No.Call Type & Description
1Call by value

This method copies the actual value of an argument into the formal parameter of the function. In this case, changes made to the parameter inside the function have no effect on the argument.

2Call by reference

This method copies the address of an argument into the formal parameter. Inside the function, the address is used to access the actual argument used in the call. This means that changes made to the parameter affect the argument.

Call Function In C Programming

By default, C uses call by value to pass arguments. In general, it means the code within a function cannot alter the arguments used to call the function.