Function

Function is a collection of statements. It means function is a block of code. Each and every c program used at least one function. Function is used to perform special type work.

C language provides more inbuilt functions. All inbuilt functions are defined by c language. Inbuilt function is called "predefine function". It is also called "library function".

That function definition is defined by user(programmer) that is called "User define function". In this tutorial we are learning "User define function".

NOTE:- you can learn predefine function or library function in different-different chapters.

Types of function

There are three types of function in c language.
(1) default function
(2) parameterize function
(3) return type function

Default function

It is also called non-parameterize function.

return-type: It tells what type value can be return from function. return type is same as data-type like void, int, float, etc.

functionName: It is the name of function. It is given by user(programmer).

Syntax

return-type functionName( ){
/* Type here block of code. */
}

How to call function?

Syntax

functionName();

Program

#include <stdio.h> 
#include <conio.h> 

void msg(){ 
 printf("\n This is default function."); 
}

void main(){
 clrscr();
 msg(); /*msg() function is calling */
 getch();
}

See Output

Below program calculate odd or even number using function.

Program

#include <stdio.h> 
#include <conio.h> 

int num; 
void readNum(){ 
 printf("\n Enter Number: "); 
 scanf("%d",&num);
}

void calculation(){ 
  int res;
 res = num % 2;
 if(res == 0){
 printf("\n %d is even number",num);
}
 else{
 printf("\n %d is odd number",num);
  }
}

void main(){
 clrscr();
 readNum();
 calculation();
 getch();
}

See Output

Parameterize Function

Syntax

return-type functionName( data-type variableName1, data-type variableName2,.......... ){
/* Type here block of code. */
}

How to call parameterize function?

Where you have called your function all parameters receive value from there respectively. You can understand from above syntaxes. variableName1 will receive data from value1 and variableName2 will receive data from value2.

Syntax

functionName(value1, vlaue2,........);

Program

#include <stdio.h> 
#include <conio.h> 

void getDataByPara(int a, int b, int c){ 
 printf("\n value of a: %d",a); 
 printf("\n value of b: %d",b);
 printf("\n value of c: %d",c);
}

void main(){ 
 clrscr();
 printf("\n This is parameterize function program."); 
 getDataByPara(10, 20, 30); /* 10, 20, 30 goes to a, b, c respectively. */
 getch();
}

See Output

Program

#include <stdio.h> 
#include <conio.h> 

int s;
void getDataByPara(int a, int b, int c){
  s = a + b + c;
 printf("\n %d + %d + %d = %d",a,b,c,s);
}

void main(){
 clrscr();
 printf("\n This is parameterize function program.");
 getDataByPara(10, 20, 30); /* 10, 20, 30 goes to a, b, c respectively. */
 getch();
}

See Output

Below program checks that a number is divided by 5 or not.

Program

#include <stdio.h> 
#include <conio.h> 

void divideBy(int a){
 int res;
 res = a % 5;
if(res == 0){
  printf("\n %d is divided by 5",a);
}
else{
  printf("\n %d is not divided by 5",a);
}
}

void main(){
  int v;
 clrscr();
 printf("\n This is parameterize function program.");
 printf("\n Enter value: ");
 scanf("%d",&v);
 divideBy(v);
 getch();
}

See Output

Optional Parameter

From below program you can understand "Optional Parameter" and "Required parameters". That parameter do not work without getting data(value) from user that is called "required parameter". It means user do not give value on parameter then compiler returns

Program

#include <stdio.h> 
#include <conio.h> 

int s;
void getDataByPara(int a, int b, int c=0, int d=0){
  s = a + b + c + d;
 printf("\n sum = %d",s);
}

void main(){
 clrscr();
 printf("\n This is parameterize function program.");
 getDataByPara(10, 20, 30); /* 10, 20, 30 goes to a, b, c respectively. */
 getch();
}

See Output

NOTE: In above program a and b is required parameter but c and d is optional parameter.

Return

"return" is a keyword. It is used to return value from function. "return" statement can be use with default function or parameterize function. A function returns only one value in one time calling. Mostly programmers use "return" as last statement.

If you have used "void" return-type then your function do not use "return" statement because void return-type do not return any value. Void is called empty return-type or data-type. It means you have used return-type excluding "void" then you can use "ret

Program

#include <stdio.h> 
#include <conio.h> 

int s;
int returnVal(int a, int b){
  s = a + b;
 return s;
}

void main(){ 
 int res;
 clrscr();
 printf("\n This is parameterize function program."); 
 res = returnVal(10, 20);
 printf("\n result = %d",res);
 getch();
}

See Output

Function

Function

Types of function

Default function

How to call function?

Parameterize Function

How to call parameterize function?

Optional Parameter

Return

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