# Structures, Unions and Bit Manipulation

## Concept of Structures

Structures are derived from different data types, **they're a collection of related variables under one name.**

- used to define records stored in files
- formation of complex data structures
- linked lists
- queues
- stacks
- trees

## Syntax

struct structure_name{
data_type member1
data_type member2
}; //remember the semicolon!

Example:

struct Person {
    char gender;
    unsigned int age;
    char name[50];
    int citNo;
    float salary;
};

## Self-Referential Structure

Structures cannot contain an instance of itself, **however pointers of the structure can be included:**

struct employee2 {
    char firstName[20];
    char lastName[20];
    unsigned int age;
    char gender;
    float hourlySalary;
    struct employee2 person; // ERROR
    struct employee2 *ePtr; // pointer
};

Pointers to reference the address of `struct employee2` can be accepted.

struct test{
  int x;
  int y;
  struct m{
    int z1;
    int z2;
  }z[2];
}a[2];

int main(){
   a[0].z[1].z1 = 5;
   printf("%d", a[0].z[1].z1);
}

## Definition

## Passing `struct` and Returning `struct` Using Functions

#include <stdio.h>

struct point {
  int x;
  int y;
}c;

struct point makepoint(struct point b){
    printf("%d %d", b.x, b.y);
    return b;
}

int main() {
    c.x = 20;
    c.y = 30;
    makepoint(c);
    return 0;
}