Variables:

1. A Variable is Nothing, but a name given to a Storage Area that our programs can manipulate.
2. Each variable in C has a specific type, which determines the Size and Layout of the Variable’s Memory; the Range of Values that can be stored within that Memory; and set of operations that can be applied to the variable.
3. The Name of a variable can be Composed of Letters, Digits, and the Underscore Character.
4. It must begin with either a Letter or an Underscore, Uppercase and Lowercase Letters are distinct because ‘C‘ is Case-Sensitive.

Type of Variables Support by ‘C’ Language:

1. Primary (Built-in) Data Types:

• int: Integer type, used for storing whole numbers.
• float: Floating-point type, used for storing numbers with a decimal point.
• double: Double-precision floating-point type, used for storing larger decimal numbers.
• char: Character type, used for storing single characters.

Example:

int age = 25;
float salary = 55000.50;
double pi = 3.14159265359;
char grade = ‘A’;

2. Derived Data Types:

• Arrays: Contiguous memory locations to store multiple values of the same data type.

         Example:

int numbers[5] = {1, 2, 3, 4, 5};

• Pointers: Variables that store memory addresses.
  Example:

int a = 10;
int *p = &a; // p now holds the address of variable a

• Structures: User-defined composite data type that groups variables of different types under a single name.
  Example:

struct Person {
char name[50];
int age;
};

• Unions: Similar to structures, but all members share the same memory location.
  Example:

union Status {
int errorCode;
char message[100];
};

3. Enumeration Data Type:

• enum: User-defined data type that consists of named integer constants.
  Example:

enum Days {Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday};

4. Void Data Type:

• void: Used to indicate that a function returns no value or that a pointer does not point to any specific type.
  Examples:

void printMessage() {
printf(“Hello, world!n”);
}

void *genericPointer;