Access Modifiers and Garbage Collection

#import<Foundation/NSObject.h>

@interface MyClass:NSObject {
	@private

    int a;
    int b;
}

   -(void) set:(int) x andb:(int) y;
   -(void) sum;
   -(void)show;

@end

#import<stdio.h>
#import"MyClass.h"
@implementation MyClass
  -(void) set:(int) x andb:(int) y {
    a=x;
    b=y;
}

-(void) sum {
printf("Sum is : %d \n",a+b);
}

-(void)show{
printf("value of a is : %d \n",a);
printf("value of b is : %d \n",b);
}
@end

#import<stdio.h>
#import"MyClass.m"
int main(){
MyClass *class1 = [[MyClass alloc] init];
MyClass *class2 = [[MyClass alloc] init];
[class1 set: 10 andb :12];
[class1 show];
[class1 sum];

// This is invalid statement because variable a is private.
// class2->a = 10;
class2->b = 15;
[class2 show];
[class2 sum];

[class1 release];
[class1 release];
return ;
}

value of a is : 10 
value of b is : 12 
Sum is : 22 
value of a is : 0 
value of b is : 15 
Sum is : 15