Functions in C


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Functions in C - Definition and Usage

  • 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.
C Function

Benefits of using function in C :

  • Functions provides reusable code.
  • In large programs of C, debugging and editing tasks is easy with the use of functions.
  • The program can be modularized into smaller parts.

Types of functions in C :

There are two types of functions in C

  • Built in(Library) Functions
  • User Defined Functions

Built in(Library) Functions :

  • These functions are provided by the system and stored in C library.
  • Example: scanf(), printf(), strcmp, strcpy, strlen, strlwr,

User Defined Functions :

  • These functions are defined by the user at the time of writing the program.

Parts of Function in C Programming :

There are three types of functions such as

  • Function Prototype (function declaration)
  • Function Definition
  • Function Call
C function definition

Function Prototype :

  • A function prototype is a function declaration that specifies the data types of its arguments in the parameter list.
  • Prototypes are syntactically distinguished from the old style of function declaration.

C Syntax

datatype functionName (Parameter List)
C function definition

Function Definition :

  • A function definition specifies the name of the function, the types and number of parameters it expects to receive, and its return type.
  • A function definition also includes a function body with the declarations of its local variables, and the statements that determine what the function does.

C Syntax

returnType functionName(Function arguments)
    //body of the function 

Function Call :

  • A function call in C , tells the compiler about a function's name, return type, and parameters , in which it defines the actual body of the function.
  • Apart from this in C , the standard library provides numerous built-in functions that our program can call.

C Syntax

function_name ( arguments list );

Sample - C Code

void addition();
void main()
void addition()
    int answer;
    int a = 5, b = 2;
    printf("The sum of two numbers is:%d\n",answer);

C Code - Explanation:

  1. In this Example, void addition(); is specified as a function declaration .
  2. Here, addition is specified as a function call that is considered as the local variable definition.
  3. Here, void addition() is said to be the calling function to get an addition values of a, b.
  4. In this example, int a = 5, b = 2 addition function returning the addition of two numbers 5 & 2 in the output statement stored in in the variable “answer”.

Sample Output - Programming Examples

  1. Here in this output “The sum of two numbers:“ is printed where its sum of 5 & 2 =7 is shown here.

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