freeCodeCamp/guide/english/c/structures/index.md

---
title: Structures
---
## Structures in C

### What are Structures?
* A **structure** is a user-defined type in C. It is based on the idea that at certain times, a programmer wants to manage not just primitive data-types, but also programmer-defined data-types.
* **Structure**, as the name suggests, consists of various primitive data-types, like character, integers, floating point variables, arrays, etc.
* **Structure** can also contain various other user-defined data types. You would learn about nested-structures next.
* **Structures** form the basis of **_object-oriented-programming_** as the concept of *class* originates from structures.
### struct keyword
* `struct` keyword can help us in defining a user-defined data type.
```C
struct StudentRecord
{
  char Name[20];
  int Class;
  char Address[30];
  char Phone[10];
};
```
* We can also define a **structure** using **typedef** which makes initializing a structure later in our program easier. Note that using typedef requires naming the structure, in the example below **struct StudentRecord** was given the name **Record**.
```C
typedef struct StudentRecord
{
  char Name[20];
  int Class;
  char Address[30];
  char Phone[10];
}Record;
```
In `main()`, the user-defined data-type **StudentRecord** is defined as:
```C
int main(void)
{
  struct StudentRecord student1;
}
```
the keyword struct must always precede **StudentRecord**, as it was not defined as a type.
Using **typedef**, only the given name is sufficient to declare a type, so the user-defined data-type looks like:
```C
int main(void)
{
  Record student1;
}
```
To access the data stored in **student1**, we use dot( **.** ) operator to access the contents of the structure type variable.
```C
int main(void)
{
  struct StudentRecord student1;
  student1.Class = 10;
  printf("Enter Name of Student\n");
  scanf("%s",&student1.Name);
  printf("Enter Address of Student\n");
  scanf("%s",&student1.Address);
  printf("Enter Phone Number of Student\n");
  scanf("%s",&student1.Phone);
  // Printing the Data
  printf("Name: %s \n, Class: %d \n, Address: %s \n, Phone: %s \n",student1.Name, student1.Class, student1.Address, student1.Phone);
}
```
We can also dynamically allocate memory for a struct, as follows:
```C
Record *student1Ptr = (Record *)malloc(sizeof(Record));
//always check for null after malloc
```
This will make malloc calculate the size of all the elements in the struct and allocate the appropriate amount of memory accordingly. To access members of a struct's pointer we use an arrow `->`
```C
int main(void)
{
  Record *student1Ptr = (Record *)malloc(sizeof(Record));
  //check for null
  student1Ptr->Class = 10;
  printf("Enter Name of Student\n");
  scanf("%s",student1Ptr->Name);
  printf("Enter Address of Student\n");
  scanf("%s",student1Ptr->Address);
  printf("Enter Phone Number of Student\n");
  scanf("%s",student1Ptr->Phone);
  // Printing the Data
  printf("Name: %s \n, Class: %d \n, Address: %s \n, Phone: %s \n",student1->Name, student1->Class, student1->Address, student1->Phone);
  free(student1Ptr);
}
```

### More Information  
https://www.tutorialspoint.com/cprogramming/c_structures.htm