16) What are Anonymous structures? Give an example.17) List out any 3 differences between static and dynamic memory allocations?18) Write an example program to demonstrate embedded nested structure?19) Write a C program to find the maximum and minimum of two numbers using macros?20) Explain the difference between arrays of structures and arrays within structures?

16. Anonymous structures are a feature of C programming language that allows the declaration of a structure without a name. These structures are useful when you want to use a structure only once in your program.

Example:

struct {
   int a;
   float b;
} x;
x.a = 10;
x.b = 20.5;

17. Differences between static and dynamic memory allocations:

• Static memory allocation is done at compile time while dynamic memory allocation is done at runtime.
• In static memory allocation, memory size is fixed while in dynamic memory allocation, memory size can be changed according to the needs at runtime.
• Static memory allocation can cause memory wastage if allocated memory is not fully utilized. In dynamic memory allocation, memory is used efficiently as it is allocated as per requirements.

18. Example program to demonstrate embedded nested structure:

#include<stdio.h>
struct date {
   int day;
   int month;
   int year;
};
struct employee {
   char name[20];
   struct date join_date;
};
int main() {
   struct employee emp;
   printf("\nEnter name: ");
   scanf("%s",emp.name);
   printf("\nEnter join date (dd mm yyyy): ");
   scanf("%d %d %d",&emp.join_date.day,&emp.join_date.month,&emp.join_date.year);
   printf("\nEmployee Details: ");
   printf("\nName: %s",emp.name);
   printf("\nJoin Date: %d/%d/%d",emp.join_date.day,emp.join_date.month,emp.join_date.year);
   return 0;
}

19. C program to find the maximum and minimum of two numbers using macros:

#include<stdio.h>
#define MAX(a,b) ((a>b)?a:b)
#define MIN(a,b) ((a<b)?a:b)
int main() {
   int num1, num2, max, min;
   printf("\nEnter two numbers: ");
   scanf("%d %d",&num1,&num2);
   max = MAX(num1,num2);
   min = MIN(num1,num2);
   printf("\nMaximum: %d",max);
   printf("\nMinimum: %d",min);
   return 0;
}

20. Difference between arrays of structures and arrays within structures:

• An array of structures is a collection of structure variables where each variable contains information about different entities. For example, an array of a structure 'student' can store information about multiple students.
• An array within a structure is a structure where one or more members are arrays. This is useful when you want to store multiple values of the same type that belong to a single entity. For example, a structure 'student' can have an array to store marks in different subjects for a single student.