Categories of function in C ?

1. function with no parameters and no return values
2. function with no parameters and return values
3. function with parameters and no return values
4. functions with parameters and return values

function with no parameters and no return values

There is no data transfer between the calling function and called function. So, calling function cannot send values and hence, called function cannot receieve the data. This is also called "void functions with no parameters".

 #include<stdio.h>
 #include<conio.h>
 void sum();
 void main()
 {                        
 sum();                    	
 getch();
 }
 void sum()
 {
 int a ,b,s;
 printf(“enter two no\n”);
 scanf(“%d%d”,&a,&b);
 s=a+b;
 printf(“%d”,s); 
 }

function with parameters and return values

there is data transfer between the calling function and called function. When parameters are passed, the called function can receieve values from the calling function. When the function returns a value, the calling function can receive a value from the called function.

 #include<stdio.h>
 #include<conio.h>
 int sum(int ,int );
 void main()
 {
 int a, b, c;
 printf(“enter Two no\n”);
 scanf(“%d%d”,&a,&b);
 c=sum(a,b);
 printf(“%d”,c);
 getch();
 }
 int sum(int  x, int  y)
 {
 int s; 
 s=x+y;
 return s;
 }

function with parameters and no return values

There is data transfer from the calling function to the called function using parameters. But, there is no data transfer from called function to the calling function.

  #include<stdio.h>
  #include<conio.h>
  void sum(int ,int );
  void main()
 {
 int a ,b;
 printf(“enter Two no\n”);
 scanf(“%d%d”,&a,&b);
 sum(a,b);
 getch();
 }
 void sum(int x, int y)
 {
 int s;
 s=x+y; 
 printf(“%d”,s);
 }