Pointers for Inter-Function Communication in C Language

We know that functions can be called by value and called by reference.

• If the actual parameter should not change in called function, pass the parameter-by value.
• If the value of actual parameter should get changed in called function, then use pass-by reference.
• If the function has to return more than one value, return these values indirectly by using call-by-reference.

Read Also: Function Call by Value in C and Function Call by Reference in C

Example

Following is the C program for the demonstration of returning the multiple values −

 Live Demo

#include<stdio.h>
void main() {
   void areaperi(int,int*,int*);
   int r;
   float a,p;
   printf("enter radius of circle:
");
   scanf("%d",&r);
   areaperi(r,&a,&p);
   printf("area=%f
",a);
   printf("perimeter=%f",p);
}
void areaperi(int x,int *p,int *q) {
   *p=3.14*x*x;
   *q=2 * 3.14*x;
}

Output

When the above program is executed, it produces the following output −

Enter radius of circle: 5
Area=78.50000
Perimeter=31.40000

Note

• Pointers have a type associated with them. They are not just pointer types, but rather are the pointer to a specific type.
• The size of all pointers is same, which is equal to size on int.
• Every pointer holds the address of one memory location in computer, but the size of a variable that the pointer refers can be different.